Horseweed (Erigeron canadensis) Flower, Leaf, Care, Uses

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Horseweed

Erigeron canadensis

Also known as: Canadian fleabane, Marestail

Horseweed is a North American herbaceous annual plant with a hairy stem, numerous pointed leaves, and waxy inflorescence. It has been naturalized in Eurasia and Australia, where it is a common weed in urban and agricultural regions. Horseweed can be used in a survival situation to start a friction fire.

Water

Twice per week

Sunlight

Full sun

Weeds

Care Guide for Horseweed

Water

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Horseweed is a drought-tolerant plant, so its water needs are minimal and it prefers drier soils. In winter, it should only be watered when its leaves shrivel. At other times of year, it should be watered only in moderation, and care should be taken to ensure that the soil never becomes too damp.

Fertilization

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Horseweed is an easy-to-care-for plant that gets all of its nutrients from the soil. It prefers loamy, fertile soils but can grow in a variety of other soil types as well. Because of this adaptability, it does not need to be fertilized at all.

Soil

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Sand, Loam, Chalky, Clay, Acidic, Neutral, Alkaline

Sunlight

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Full sun, Partial sun

Hardiness Zones

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3 to 10

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Horseweed

Water

Twice per week

Sunlight

Full sun

Hardiness Zones

3 to 10

Planting Time

All year around

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Questions About Horseweed

Watering

Pruning

Sunlight

Temperature

Fertilizing

What is the best way to water my Horseweed?

To water Horseweed, you can use a garden hose with a spray nozzle, a watering can, or just about any other common watering tool. Generally, Horseweed is not too picky about how they receive their water, as they can live off of rainwater, tap water, or filtered water. Often, you should try not to water this plant from overhead, as doing so can damage the leaves and flowers and may lead to disease as well. At times, the best method for watering this plant is to set up a drip irrigation system. These systems work well for Horseweed as they apply water evenly and directly to the soil. For one Horseweed that grows in a container, you can use a similar watering approach while changing the tools you use. To water a container-grown Horseweed, use a cup, watering can, or your tap to apply water directly to the soil.

What should I do if I water my Horseweed too much or too little?

The remedy for underwatering Horseweed is somewhat obvious. When you notice that your plant lacks moisture, simply begin watering it on a more regular basis. The issue of overwatering can be a much more dire situation, especially if you fail to notice it early. When your Horseweed is overwatered, it may contract diseases that lead to its decline and death. The best way to prevent this outcome is to choose a proper growing location, one that receives plenty of sunlight to help dry the soil and has good enough drainage to allow excess water to drain rather than pooling and causing waterlogged soils. If you overwater your Horseweed that lives in a pot, you may need to consider changing it to a new pot. Your previous container may not have contained soil with good drainage or may not have had sufficient drainage holes. As you repot your overwatered Horseweed, make sure to add loose soils and to use a pot that drains efficiently.

How often should I water my Horseweed?

Horseweed needs water regularly throughout the growing season. Beginning in spring, you should plan to water this plant about once per week. As the season presses on and grows warmer, you may need to increase your watering rate to about two to three times per week. Exceeding at this rate can be detrimental to your Horseweed. With that said, you should also ensure that the soil in which your Horseweed grows remains relatively moist but not wet, regardless of how often you must water to make that the case. Watering Horseweed that lives in a pot is a bit different. Generally, you'll need to increase your watering frequency, as the soil in a pot can heat up and dry out a bit faster than ground soil. As such, you should plan to water a container-grown Horseweed a few times per week in most cases, versus just once per week for an in-ground plant.

How much water does my Horseweed need?

There are a few different ways you can go about determining how much water to give to your Horseweed. Some gardeners choose to pick their water volume based on feeling the soil for moisture. That method suggests that you should water until you feel that the first six inches of soil have become moist. Alternatively, you can use a set measurement to determine how much to water your Horseweed. Typically, you should give your Horseweed about two gallons of water per week, depending on how hot it is and how quickly the soil becomes dry. However, following strict guidelines like that can lead to overwatering if your plant requires less than two gallons per week for whatever reason. When growing Horseweed in a container, you will need to use a different method to determine how much water to supply. Typically, you should give enough water to moisten all of the layers of soil that have become dry. To test if that is the case, you can simply stick your finger in the soil to feel for moisture. You can also water the soil until you notice a slight trickle of excess water exiting the drainage holes of your pot.

How can I tell if i'm watering my Horseweed enough?

It can be somewhat difficult to avoid overwatering your Horseweed. On the one hand, these plants have relatively deep roots that require you to moisten the soil weekly. On the other hand, Horseweed are plants that are incredibly susceptible to root rot. Along with root rot, your Horseweed may also experience browning as a result of overwatering. Underwatering is far less likely for your Horseweed as these plants can survive for a while in the absence of supplemental watering. However, if you go too long without giving this plant water, it will likely begin to wilt. You may also notice dry leaves.

How should I water my Horseweed through the seasons?

You can expect your Horseweed’s water needs to increase as the season moves on. During spring, you should water about once per week. Then, as the summer heat arrives, you will likely need to give a bit more water to your Horseweed, at times increasing to about three times per week. This is especially true of Horseweed that grow in containers, as the soil in a container is far more likely to dry out faster than ground soil when the weather is warm. In autumn, while your Horseweed is still in bloom, it may need a bit less water as the temperature has likely declined, and the sun is no longer as strong as it was in summer.

How should I water my Horseweed at different growth stages?

Horseweed will move through several different growth stages throughout the year, some of which may require more water than others. For example, you will probably start your Horseweed as a seed. While the seed germinates, you should plant to give more water than your Horseweed will need later in life, watering often enough to maintain consistent soil moisture. After a few weeks, your Horseweed will grow above the soil and may need slightly less water than at the seedling phase. Then, once this plant is mature, you can begin to use the regular watering frequency of about once per week. As flower development takes place, you may need to give slightly more water to aid the process.

What's the difference between watering Horseweed indoors and outdoors?

There are several reasons why most Horseweed grow outdoors rather than indoors. The first is that these plants typically grow to tall. The second reason is that Horseweed needs more daily sunlight than most indoor growing locations can provide. If you are able to provide a suitable indoor growing location, you may find that you need to give your Horseweed water a bit more often than you would in an outdoor growing location. Part of the reason for this is that indoor growing locations tend to be a lot drier than outdoor ones due to HVAC units. The other reason for this is that soil in containers can dry out relatively quickly as well compared to soil in the ground.

Is pruning necessary for my Horseweed?

Horseweed is a kind of annual plant so it doesn't need much pruning. You only need to cut off and clean the diseased, yellow or dropped leaves and stems during its growing period. This will help your Horseweed to stay away from pathogens infection.

How do I prune my Horseweed?

During the growth of the plant, yellowing, drying and spotted leaves are produced, and these spotted and discolored leaves need to be trimmed off. If the whole piece of leave is discolored or infected, you will need to cut it off completely. In other situations, you will only need to cut off the discolored or infected part on certain leaves. Horseweed above the ground will die and dry up in the winter, and the dead plants need to be cleaned up.

Are there any cautions I should be careful with when pruning my Horseweed?

Horseweed leaves are delicate, so take care not to score or bruise them. Unless the leaves are withered or heavily discolored, do not prune the leaves from the lowermost branches unless they’re damaged. They typically grow the largest, so they supply the plant with critical energy to keep it growing right. Please prevent the wounds from water after pruning until they are fully recovered. Remember always sterilize the tools before pruning. When the pruning is finished, please throw all the waste leaves and stems into the trashbins to avoid diseases and bugs.

Are there any tips for pruning my Horseweed?

Sterilize all the tools before pruning; unclean tools will pass pathogens to the plant through wounds;
Prune on sunny days because the new cuts will be infected by pathogens if they're distained by rain or water.
Throw all the waste leaves and stems into trashbins, they will easily rot and attract diseases and bugs

When should/shouldn't I prune my Horseweed?

Expect to prune your Horseweed every week if it’s growing well or every two weeks if it grows slowly. It is always good to prune it on sunny days because if you prune it on rainy days, the rainwater will distain the cuts and cause the whole plant to be infected.

What should I look for when pruning my Horseweed in different seasons?

Because Horseweed is an annual plant, the pruning should take place basically during the seasons that the plant grows rapidly. During the growth of the plant, yellowing, drying and spotted leaves are produced, and these spotted and discolored leaves need to be trimmed off.

How much sunlight should Horseweed get per day to grow healthily?

You must expose the plants to at least 6 to 8 hours of sunlight daily. They prefer more exposure to the morning light, especially in the summer. The Horseweed needs full sun and more sunlight that it can get. The more light these species get, the more they can manufacture food, produce beautiful blooms, and survive.

What type of sunlight does Horseweed need?

The Horseweed grows best under full sunlight. It's best not to crowd them together so they can get exposure to the sun evenly. The leaves shouldn't be starved with sunlight. If planted in pots, try to expose the herbaceous flowers in windows with direct sun and ensure they receive full sunlight regardless of the months.

They don't tend to do well in partial or filtered light as this will not produce strong stems and healthy flowers. It's best if the Horseweed is always exposed to the sun.

Can sunlight hurt plants? How to protect Horseweed from sun and heat damage?

When the temperature rises above 90℉(32℃), the Horseweed can get damaged by extreme temperatures, especially if they are exposed to many hours of sun. It's always ideal for providing some shade from the light in the afternoon in the summer. It's always important to keep in mind that the sunlight in the summer is stronger than the one in the winter. Sunlight exposure is also 50% longer in the summer than in the winter.

If the Horseweed is too stressed with sunlight, you might want to keep them fully hydrated. Water them when the top of the soil is about 2 inches dry, and move the plants indoors if it's too hot outside. This is the case if they are planted in containers.

It can be normal for the plant leaves to wilt during the day. Generally, they can recover at night. However, when you notice that the Horseweed is still drooping, this means that the plant is losing water fast, and you need to water them.

Should I protect Horseweed from sun exposure?

The Horseweed does not need any protection from the sun. In fact, they love the sun, and some species are heliotropic. Plant them in south-facing gardens whenever possible so they can be exposed from morning to afternoon. While the sun can benefit them, some may experience a sunburn. You might offer protection from the afternoon and midday sun through a shade of a tree or a wall.

Growing the Horseweed in shady areas is impossible because the larger flowers would require a lot of energy to grow and produce. Always provide the lighting conditions and set them in an area with full sun for best results.

What will happen if Horseweed gets inadequate sunlight?

When the Horseweed does not get adequate sunlight, or they are not placed in full sun locations, it's worth noting that the photosynthetic process will slow down. A lack of sunlight will cause the stems to become more leggy since they become thin and long since they tend to seek too much sunlight. They will not bloom and produce seeds in the shade.

Inadequate sunlight will also mean that the older leaves can die, the color of the new ones is lighter than the old foliage, and the new growth is smaller than the last ones.

The Horseweed indeed loves the sun so much. However, they can wilt when exposed to excessive heat and ultraviolet light during the extreme summer months, so be careful. You might want to cover them with a net that has a green shade, especially in the summer, to prevent the leaves and the flowers from scorching. When they are indoors, reduce the heat with the help of a fan.

Does Horseweed need special care about sunlight during its different growth stages?

When the Horseweed is growing, they need more light than their mature counterparts. The younger ones should receive adequate light, but they might not be prepared for sudden full sunlight, especially if they are grown in a nursery. They can be more sensitive to the summer sun, so the lighting should be gradual and slow.

How much light does Horseweed need for photosynthesis?

During summer or late spring, the Horseweed needs 6 to 8 hours of direct light every single day. This is whether they are planted outdoors. If the Horseweed is planted in pots or you're growing them in the winter, they need direct fluorescent lights that help them grow better. Make sure to place them in an indoor area where they are facing south or east so they can have enough sunlight for photosynthesis.

Are there any cautions or tips for sunlight and Horseweed?

When transplanting the plants, they should not be exposed to sudden sunlight. Give the Horseweed to grow and mature before transplanting outside. Some species of herbaceous plants can grow taller and might cast a shade on other young plants. Allow between 80 to 100 days of growing season before planting another batch to ensure that every plant receives more than enough sunlight for at least 6 hours a day.

Make sure that the Horseweed receives the best light possible, especially if it's planted in a nursery. These are sun-loving plants, but too much sunlight with a very hot temperature is also detrimental to their growth. Indoor lights should be replaced with natural sunlight as much as possible since these species crave this every day.

What is the optimal temperature for Horseweed?

The best temperature for Horseweed depends on the time of year. There are two primary seasons to discuss for temperature: the growing season, and the dormancy season. During the growing season, once Horseweed has begun to sprout, the ideal temperature range should be anywhere from 65~80℉(18~27℃). Any colder than 15℉(-10℃), and the plant will suffer; its leaves may brown and wilt, but if this is a short cold snap, then Horseweed may be able to survive with some help.

During the warmer parts of the year, Horseweed will need to be similarly protected from temperatures that are too high. 95-105℉ (35-40℃) is the top of this plant’s temperature range, and anything above that will compromise the integrity of the foliage and blooms of Horseweed. Hotter temperatures can cause wilting, drooping, and even sunburn on the leaves, which can be difficult for Horseweed to recover from. There are quite a few ways to combat this issue that are quick and easy!

Temperature requirements for first year or seedling Horseweed

If this is the first year of your Horseweed outside as a new plant, then it may need a little extra tending during the coldest months of the year. Not only can frost more severely damage a first-year Horseweed, but it can also prevent it from growing back as a healthy plant come spring. This plant needs to be kept at 40℉(5℃) or above when they’re not yet established, which can be done either by bringing your Horseweed inside for a month or two, or putting up mulch or fabric barriers that protect from frost damage.

It’s also a good idea to plant Horseweed in a shadier spot during the first year or two, as smaller and weaker plants have a more difficult time maintaining their own temperatures in the heat. First-year Horseweed should receive no more than five hours of direct sunlight per day, particularly if the ambient daytime temperature gets above 80℉(27℃). Shadecloth and frequent watering or misting are the keys to summer heat control.

How can I protect Horseweed from extreme temperatures?

If cold temperatures (below 15℉(-10℃)) do occur during the growing season, there are a few measures you can take to help protect Horseweed from frost or cold damage. If you’re growing Horseweed in a container, then the container can simply be brought inside in bright, indirect light until the temperatures rise up over the lower threshold again. Another option that’s better suited for ground-planted Horseweed is to use mulch or horticultural fabric to create an insulated barrier around the plant, which will protect the plant from frost and cold wind.

For temperatures that are hotter than 80℉(27℃) in the shade during the day, be careful to only expose Horseweed to six hours or less of sunlight per day, preferably in the morning hours. Putting up shade cloth, or a fine plastic mesh, can help reduce the amount of direct sunlight that hits the plant during the hottest parts of the day. You can also install a misting system that allows for a slow release of cooling mist around the base of the plant during the day to lower ground temperatures.

Dormant season temperature recommendations for Horseweed

During the cold winter months, Horseweed needs a certain measure of cold in order to stay in dormancy until it’s time to sprout. Sprouting too early, that is before the danger of the last frost has passed, can be fatal to Horseweed, especially if it’s already had a head start when the frost hits. Winter temperatures should ideally stay below 32℉(0℃), but if they get up to 40℉(5℃), everything will be just fine.

An unexpected warm spell during the cold months, which can happen in more temperate climates like woodland rainforests, can trigger a premature sprout from Horseweed. In this case, if there’s still imminent danger of frost, you may want to try covering it with clear plastic on stakes so that the cold has less of a chance of damaging the new sprout. This setup can be removed when the danger of frost has passed. Occasionally, Horseweed will be able to resprout at the correct time without any help, but this method increases the chances of a successful second sprouting.

Why do I need to fertilize my Horseweed?

All plants need nutrients to grow, but some types are able to take what they need and don’t need any supplementation with fertilizers. Horseweed, like other plants, use nutrients to support growth and all internal processes.

Each of the main nutrients that plants use (nitrogen, phosphorus, and potassium) contribute to one or more of a plant’s essential functions, and in the case of foliage it is nitrogen that provides the most support. It can be difficult for a Horseweed to get enough nitrogen from the soil, which is why many gardeners prefer to supplement by feeding Horseweed with a source of nitrogen.

When is the best time to fertilize my Horseweed?

Horseweed generally grows well, but a fertilizer can be applied about once a month to give the plant a boost when it is actively growing. You should fertilize Horseweed about once a month only during the spring and summer months, but not during fall and winter when it becomes less active and does not use as many nutrients.

You’ll know when to start fertilizing Horseweed if you see signs of new growth. The fertilization schedule remains the same whether the plant is grown outside or indoors in a container. However, if your Horseweed is in a container, you probably will not need to fertilize for the first one to two months. Potting soil made for container plants already contains plenty of nutrients, so you should only start to fertilize after your plant has been in the same soil for a while.

When should I avoid fertilizing my Horseweed?

Never fertilize your Horseweed if it is not healthy, for example if it has developed a disease or has insect pests on it. Also do not fertilize a dehydrated plant, since the fertilizer will make this problem even worse. Only fertilize healthy plants.

Do not splash fertilizer onto the leaves or stem of this plant when watering, since it can cause burned spots. Be careful not to allow the fertilizer to make direct contact with the plant, unless you are usually a special fertilizer designed to be applied to the foliage.

What type of fertilizer does my Horseweed need?

Fertilizers contain high levels of nitrogen, potassium and phosphorus, along with other essential nutrients such as iron, manganese and zinc. These are all necessary elements that promote growth in Horseweed.

A balanced fertilizer works well for Horseweed, for example an all-purpose fertilizer with a 10-10-10 NPK number. For natural fertilizers, blood meal or worm castings work well. You may also choose a fertilizer that is higher in nitrogen than other nutrients, such as fish fertilizer. Nitrogen provides support to leaves, which are the main feature that people want from Horseweed. There is no point in providing a lot of supplements for flowers or seeds if that is not your purpose in growing the plant.

How do I fertilize my Horseweed?

Apply fertilizer based on the instructions on the particular type you have purchased. It is generally a good idea to start with half-strength fertilizer to avoid accidentally over-fertilizing your Horseweed. Since this plant requires frequent fertilization, it is common to accidentally fertilize too much. Remember that it’s always easier to add more fertilizer than it is to try to save an over-fertilized plant.

Don’t apply fertilizer to dry soil - it should already be at least somewhat moist before fertilizing. This helps the fertilizer absorb more easily and helps avoid fertilizer burn. You should also water after applying dry fertilizers to your soil.

Some fertilizers are meant to be mixed into the soil when planting, while others are applied on top of the soil and then watered in. For most types of Horseweed, a water soluble fertilizer is an easy choice. Simply mix the fertilizer solution into your watering can at the recommended dosage for Horseweed and then water the plant as usual. Slow-release granules or fertilizer spikes can also work well if you prefer not to remember to fertilize monthly.

What happens if I fertilize my Horseweed too much?

Over-fertilization leads to a build-up of salts in the soil which leads to a lack of vitality overall and pale coloration in the leaves. Leaves may also wilt or develop brown tips as the excess salt from the fertilizer tries to make its way out of the leaves.

Too much fertilizer makes it impossible for the plant to take up water and nutrients, which will eventually kill it if you don’t take steps to save your Horseweed. If the Horseweed is in a container, you could either remove it from the pot and repot it in fresh potting mix, or flush out the soil by running a lot of water through and letting it drain out thoroughly.

If your Horseweed is outdoors, the same theory applies, although it can be more difficult to flush outdoor soil. Water thoroughly and hold off on fertilizing again for a while. You may want to perform a soil test before you add any more fertilizer to make sure you don’t provide too much of any one nutrient.

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More About How-Tos

Explore 5 of plant how-tos on Feng shui direction, Water, Lighting, Temperature, Transplant, etc.

Feng shui direction

Southwest

Horseweed contributes subtly yet significantly to the chi flow, potentially enhancing the overall harmony of a space. When placed in a Southwest-facing direction, it may foster stability and strength, courtesy of its inherent earth-centric qualities often associated with this particular orientation. However, the outcomes may vary due to numerous underlying factors, making each experience inherently unique.

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Water

Twice per week

Horseweed originates from regions with seasonal climates, preferring evenly moist soil. Ensure to water only when necessary to prevent overwatering, and always check soil moisture beforehand.

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Lighting

Full sun

Horseweed has a strong appetite for plentiful sun exposure to thrive. Its growth significantly benefits from the radiant energy of the sun. However, its resilience allows it to also grow in areas with somewhat lower sun levels. In its native habitat, it's often seen in locations with ample sunshine. Unreasonably low or high light exposure can hamper its proper growth.

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Temperature

-10 to 35 ℃

Horseweed is native to areas with moderate climates and performs best in temperatures ranging between 68 to 95 °F (20 to 35 ℃). Adjustments regarding temperatures in varying seasons may be necessary to replicate these conditions.

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Transplant

1-2 feet

Transplant horseweed ideally during the balmy window of mid-spring to early summer. Choose a well-draining location with adequate sunlight. For best results, acclimate seedlings to outdoor conditions and keep soil evenly moist.

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Common Pests & Diseases

Common issues for Horseweed based on 10 million real cases

Flower withering

Flowers may dry out due to a sudden change in environment or because the plant has completed its normal flowering period.

Solutions: If flower withering is a natural progression due to age, there is nothing that can be done to slow or stop the process. Once hormones within the plant begin the process of senescence, it’s irreversible. For lack of water, immediately water the plant using room temperature rainwater, bottled spring water, or filtered tap water. Water container plants until excess water drains out the bottom; water in-ground plants until the soil is soaked but there isn’t standing water on the surface. In the event of nutritional deficiencies, the best solution is to use a granular or water-soluble liquid fertilizer, and apply it to the soil at about half the recommended dosage. Keep it off the leaves and make sure granular products are watered into the soil well. If the plant is infected with a bacterial or fungal pathogen, there is no course of treatment that cures the diseased plants. The best solution is to remove the infected plants and dispose of the plant material off-site. Do not put in a compost pile.

Leaf beetles

Leaf beetles are a class of colored insects 1 to 2 cm in size. They gnaw on leaves and petals resulting in small, round holes scattered over the surface.

Solutions: For less serious cases: Remove beetles, nymphs, and eggs. Remove all life stages of the beetles and kill them by placing them in a bucket of warm, soapy water. This can be done more easily by placing the bucket under affected leaves and shaking the plant. This method is most effective in the afternoon when leaf beetles are more active. Always dispose of insects in a sealed bag or container to avoid escape and spread. To treat more serious infestations: Apply organic insecticides. Use naturally-derived insecticides before moving on to synthetic insecticides. Neem oil and pyrethrum are naturally-derived insecticides that should be applied following label instructions. Apply synthetic insecticides. Examples of insecticides effective for leaf beetles include carbaryl, permethrin, and bifenthrin. Apply insecticides according to label instructions.

Plant dried up

The entire plant may dry out due to dieback or normal seasonal dormancy.

Solutions: The solution for a dried out plant depends on the cause, so determine the cause before selecting a treatment method. Adjust your watering: Stick your finger in the soil near the roots. If it feels bone dry or overly saturated, you need to adjust your watering frequency accordingly. Prune back dead foliage: Snip off any brown stems and leaves on the plant to make space for new growth. This encourages the roots to send up fresh stems. Move to a proper environment. This may involve decreasing or increasing sun exposure, depending on the species. Decrease fertilizer applications. If you have applied too much fertilizer, you can repot plants with fresh potting soil. Wait. If your plant has dried out as daylight is decreasing, it is entering dormancy. Decrease watering and wait until the plant resumes growth.

Brown spot

This infection can cause brown spots or patches to appear on the plant.

Solutions: In minor cases of brown spot, there isn’t any need to treat the disease. However, if much of the foliage is affected and defoliation occurs, the plant will benefit from getting rid of the infection. It is recommended to start by applying organic treatment options, working up to the more potent synthetic, chemical fungicides if necessary. Organic options won’t kill the fungus, but will prevent it from spreading. Dissolve ½ teaspoon of baking soda and one teaspoon of liquid soap in a gallon of water. Using a spray bottle, spray on tops and bottoms of leaves until the mixture drips off. Repeat every two weeks until existing spots stop enlarging and new spots no longer appear. Spray a copper-based fungicidal soap on the leaves, coating the top and bottom leaf surfaces. Reapply as directed on the product label. Copper penetrates the leaf surface and prevents germination of spores so the fungus cannot spread. Apply an all-purpose fungicide to the entire plant, following the label instructions carefully.

Leaf rot

This pathogen can cause the leaves to rot.

Solutions: Bacterial infections need to be treated quickly to prevent the spread to neighboring, healthy plants, potentially wiping out large sections of your indoor or outdoor garden. In mild cases: Use sterilized (10% bleach solution) pruning shears or scissors to remove any infected plant parts, making sure to dispose of them off site. Use a copper-based bactericide to treat the unaffected foliage, as well as the soil, and neighboring plants. Follow the manufacturer’s rate and timing directions found on the product label. In severe cases, where more than half the leaves are affected: Remove all of the infected plants from the garden, disposing of them off site. Treat the soil and neighboring plants using a copper-based bactericide. Follow the manufacturer’s rate and timing directions found on the product label.

Aged yellow and dry

Natural aging can cause leaves to turn yellow and dry out.

Solutions: If the yellowing and drying of leaves and flowers is a natural progression due to age, nothing can be done to slow or stop the process. Once hormones within the plant begin the process of senescence, it’s irreversible.

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Weed Control

Weeds

Horseweed is a common landscape and agricultural weed, mainly found on undisturbed lands. It is infamous for being the first weed to develop resistance to the widely used herbicide, glyphosate. What's more, the germination time is flexible, so horseweed can emerge in all seasons except winter, and the seeds spread efficiently like dandelion seeds. Horseweed has been spreading outside of its native range for centuries and can now be found in grasslands, fields, and many disturbed areas in Europe, Asia, Australia, northern Africa, and tropical parts of the Americas. It is considered an agricultural weed both in its native and naturalized range.

How to Control it

Once the weeds start to flower and fructify, it will be difficult to control them effectively. In fact, the best time to remove weeds is before flowering and fructification because the seeds will spread rapidly after that. So, it is necessary to remove weeds more often and to take precautions in advance next year. Horseweed is resistant to many herbicides, such as glyphosate. Hence, chemical removal methods are not necessarily effective. However, its propagation can still be controlled by pulling out the root system and pruning frequently. Different methods of removal can be chosen based on different periods. Mulching: During the seed stage, covering with sawdust, straws or black mulches to effectively inhibit seed germination and the growth of the seedling. Generally, this method is used in winter or spring to inhibit the germination of weed in the soil. If the weeds have already flowered and fructified, this method can be used to isolate the seeds and the soil to prevent the seeds from falling into the soil. Pulling out: Before the weeds fructify, wear gloves or use tools to pull them out. If it is difficult to pull out weed due to dry soil, adding water to the soil helps to make it easy to remove the roots thoroughly. After pulling out the weed, deep tillage can be adopted to remove the residual roots. This method is especially effective for weeds that are in the seedling stage or low growing size. Pruning: Pruning weeds before they fructify can effectively control the propagation of weeds. Frequent pruning can inhibit the growth and fructification of weeds and effectively them in the same year. Note: When removing weeds, it is necessary to wear gloves to avoid direct contact with the weeds, especially for the ones that are poisonous, thorny and allergenic. When removing weeds at the flowering stage, special masks should be worn to prevent allergic reactions caused by the inhalation of pollen.

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Distribution Map

Habitat

Waste and cultivated land, walls

Native

Cultivated

Invasive

Potentially invasive

Exotic

No species reported

More Info

Plant Type

Herb

Flower Color

White

Yellow

Bloom Time

Summer, Fall

Leaf Color

Green

Name story

Mare's tail||Horseweed

If you observe the plant closely, you discover that its stalk has many branches and the branches all grow upwards. What makes it magical is that each branch is covered with short hairs. When the sun shines on it, the shadow cast on the ground looks like a horse tail. So, it is called mare's tail or horseweed.

Symbolism

Sanctity, purification, driving away the unwanted

Usages

Garden Use

Horseweed is a tolerant, low-maintenance plant. Often used in the garden to attract wildlife and pollinators, this plant can be put in a sunny or partially shaded area with well-draining soils. Horseweed is drought-tolerant and can be planted in areas where erosion control is needed.

Scientific Classification

Phylum

Vascular plants

Class

Dicotyledons

Order

Asters bellflowers fanflowers and allies

Family

Daisy

Genus

Fleabanes

Species

Horseweed

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Plan your green oasis based on your criteria: plant type, pet safety, skill level, sites, and more.

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Add to My Garden

Horseweed

Erigeron canadensis

Also known as: Canadian fleabane, Marestail

Water

Twice per week

Sunlight

Full sun

Weeds

Care Guide for Horseweed

Water

Fertilization

Soil

Sand, Loam, Chalky, Clay, Acidic, Neutral, Alkaline

Sunlight

Full sun, Partial sun

Hardiness Zones

3 to 10

Know the light your plants really get.

Find the best spots for them to optimize their health, simply using your phone.

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Questions About Horseweed

Watering

Pruning

Sunlight

Temperature

Fertilizing

What is the best way to water my Horseweed?

What should I do if I water my Horseweed too much or too little?

How often should I water my Horseweed?

How much water does my Horseweed need?

How can I tell if i'm watering my Horseweed enough?

How should I water my Horseweed through the seasons?

How should I water my Horseweed at different growth stages?

What's the difference between watering Horseweed indoors and outdoors?

Is pruning necessary for my Horseweed?

How do I prune my Horseweed?

Are there any cautions I should be careful with when pruning my Horseweed?

Are there any tips for pruning my Horseweed?

When should/shouldn't I prune my Horseweed?

What should I look for when pruning my Horseweed in different seasons?

How much sunlight should Horseweed get per day to grow healthily?

What type of sunlight does Horseweed need?

Can sunlight hurt plants? How to protect Horseweed from sun and heat damage?

Should I protect Horseweed from sun exposure?

What will happen if Horseweed gets inadequate sunlight?

Does Horseweed need special care about sunlight during its different growth stages?

How much light does Horseweed need for photosynthesis?

Are there any cautions or tips for sunlight and Horseweed?

What is the optimal temperature for Horseweed?

Temperature requirements for first year or seedling Horseweed

How can I protect Horseweed from extreme temperatures?

Dormant season temperature recommendations for Horseweed

Why do I need to fertilize my Horseweed?

When is the best time to fertilize my Horseweed?

When should I avoid fertilizing my Horseweed?

What type of fertilizer does my Horseweed need?

How do I fertilize my Horseweed?

What happens if I fertilize my Horseweed too much?

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Keep your plants happy and healthy with our guide to watering, lighting, feeding and more.

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More About How-Tos

Common Pests & Diseases

Common issues for Horseweed based on 10 million real cases

Flower withering

Flowers may dry out due to a sudden change in environment or because the plant has completed its normal flowering period.

Learn More

Leaf beetles

Leaf beetles are a class of colored insects 1 to 2 cm in size. They gnaw on leaves and petals resulting in small, round holes scattered over the surface.

Learn More

Plant dried up

The entire plant may dry out due to dieback or normal seasonal dormancy.

Learn More

Brown spot

This infection can cause brown spots or patches to appear on the plant.

Learn More

Leaf rot

This pathogen can cause the leaves to rot.

Learn More

Aged yellow and dry

Natural aging can cause leaves to turn yellow and dry out.

Learn More

Treat and prevent plant diseases.

AI-powered plant doctor helps you diagnose plant problems in seconds.

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Weed Control

Weeds

How to Control it

Do you have weeds in your garden?

Differentiate them from your plants by a picture, and learn how to control them.

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Distribution Map

Habitat

Waste and cultivated land, walls

Map

Native

Cultivated

Invasive

Potentially invasive

Exotic

No species reported

More Info

Plant Type

Herb

Flower Color

White

Yellow

Bloom Time

Summer, Fall

Leaf Color

Green

Name story

Mare's tail||Horseweed

Symbolism

Sanctity, purification, driving away the unwanted

Usages

Garden Use

Scientific Classification

Phylum

Vascular plants

Class

Dicotyledons

Order

Asters bellflowers fanflowers and allies

Family

Daisy

Genus

Fleabanes

Species

Horseweed

Find your perfect green friends.

Plan your green oasis based on your criteria: plant type, pet safety, skill level, sites, and more.

Download the App

Related Plants

Alternanthera brasiliana

Discover more articles?

Indoor

Requirements

Full sun

Ideal

Above 6 hours sunlight

Partial sun

Tolerance

About 3-6 hours sunlight

Watch how sunlight gracefully moves through your garden, and choose spots that provide the perfect balance of light and shade for your plants, ensuring their happiness.

Essentials

Preferred

Tolerable

Unsuitable

Know the light your plants really get.

Find the best spots for them to optimize their health, simply using your phone.

Download the App

Artificial lighting

Indoor plants require adequate lighting for optimal growth. When natural sunlight is insufficient, particularly in winter or in less sunny spaces, artificial lights offer a vital solution, promoting faster, healthier growth.
1. Choose the right type of artificial light: LED lights are a popular choice for indoor plant lighting because they can be customized to provide the specific wavelengths of light that your plants need.
Full sun plants need 30-50W/sq ft of artificial light, partial sun plants need 20-30W/sq ft, and full shade plants need 10-20W/sq ft.
2. Determine the appropriate distance: Place the light source 12-36 inches above the plant to mimic natural sunlight.
3. Determine the duration: Mimic the length of natural daylight hours for your plant species. most plants need 8-12 hours of light per day.

Important Symptoms

Insufficient light

Horseweed, a plant that thrives in full sunlight, is commonly grown outdoors with ample sunlight. When cultivated indoors with inadequate light, it may exhibit subtle symptoms of light deficiency.

(Symptom details and solutions)

Small leaves

New leaves may grow smaller in size compared to the previous ones once they have matured.

Leggy or sparse growth

The spaces between leaves or stems of your horseweed may become longer, resulting in a thin and stretched-out appearance. This can make the plant look sparse and weak, and it may easily break or lean due to its own weight.

Faster leaf drop

When plants are exposed to low light conditions, they tend to shed older leaves early to conserve resources. Within a limited time, these resources can be utilized to grow new leaves until the plant's energy reserves are depleted.

Slower or no new growth

Horseweed enters a survival mode when light conditions are poor, which leads to a halt in leaf production. As a result, the plant's growth becomes delayed or stops altogether.

Lighter-colored new leaves

Insufficient sunlight can cause leaves to develop irregular color patterns or appear pale. This indicates a lack of chlorophyll and essential nutrients.

Solutions

1. To ensure optimal growth, gradually move plants to a sunnier location each week, until they receive at least 6 hours of direct sunlight daily. Use a south-facing window and keep curtains open during the day for maximum sunlight exposure and nutrient accumulation.2. To provide additional light for your plant, consider using artificial light if it's large or not easily movable. Keep a desk or ceiling lamp on for at least 8 hours daily, or invest in professional plant grow lights for ample light.

Excessive light

Horseweed thrives in full sun exposure and can tolerate intense sunlight. With their remarkable resilience, symptoms of sunburn may not be easily visible, as they rarely suffer from it.

(Symptom details and solutions)

Chlorosis

Chlorosis is a condition where the plant's leaves lose their green color and turn yellow. This is due to the breakdown of chlorophyll from excessive sunlight, which negatively affects the plant's ability to photosynthesize.

Sunscald

Sunscald occurs when the plant's leaves or stems are damaged by intense sunlight exposure. It appears as pale, bleached, or necrotic areas on the plant tissue and can reduce the plant's overall health.

Leaf Curling

Leaf curling is a symptom where leaves curl or twist under extreme sunlight conditions. This is a defense mechanism used by the plant to reduce its surface area exposed to sunlight, minimizing water loss and damage.

Wilting

Wilting occurs when a plant loses turgor pressure and its leaves and stems begin to droop. Overexposure to sunlight can cause wilting by increasing the plant's water loss through transpiration, making it difficult for the plant to maintain adequate hydration.

Leaf Scorching

Leaf scorching is a symptom characterized by the appearance of brown, dry, and crispy edges or patches on leaves due to excessive sunlight. This can lead to a reduction in photosynthetic capacity and overall plant health.

Solutions

1. Move your plant to the optimal position where it can receive abundant sunlight but also have some shade. An east-facing window is an ideal choice as the morning sunlight is gentler. This way, your plant can enjoy ample sunlight while reducing the risk of sunburn.2. It is recommended to trim off any completely dehydrated or withered parts of the plant.

Discover information about plant diseases, toxicity, weed control and more.

Indoor

Requirements

Ideal

Tolerable

Unsuitable

Just like people, each plant has its own preferences. Learn about your plants' temperature needs and create a comforting environment for them to flourish. As you care for your plants, your bond with them will deepen. Trust your intuition as you learn about their temperature needs, celebrating the journey you share. Lovingly monitor the temperature around your plants and adjust their environment as needed. A thermometer can be your ally in this heartfelt endeavor. Be patient and gentle with yourself as you explore your plants' temperature needs. Cherish your successes, learn from challenges, and nurture your garden with love, creating a haven that reflects the warmth of your care.

Essentials

Regional wintering strategies

Horseweed has strong cold resistance, so special frost protection measures are usually not necessary during winter. However, if the winter temperatures are expected to drop below {Limit_growth_temperature}, it is still important to provide cold protection. This can be achieved by covering the plant with materials such as soil or straw. Before the first freeze in autumn, it is recommended to water the plant abundantly, ensuring the soil remains moist and enters a frozen state. This helps prevent drought and water scarcity for the plant during winter and early spring.

Important Symptoms

Low Temperature

Horseweed is cold-tolerant and thrives best when the temperature is above {Suitable_growth_temperature_min}. During winter, it should be kept above {Tolerable_growing_temperature_min}. When the temperature falls below {Limit_growth_temperature}, although there may not be any noticeable changes during winter, there may be a decrease in sprouting or even no sprouting during springtime.

Solutions

In spring, remove any parts that have failed to sprout.

High Temperature

During summer, Horseweed should be kept below {Suitable_growth_temperature_max}. When the temperature exceeds {Tolerable_growing_temperature_max}, the leaves of the plant may become lighter in color, prone to curling, susceptible to sunburn, and in severe cases, the entire plant may wilt and become dry.

Solutions

Trim away the sunburned and dried-up parts. Move the plant to a location that provides shade from the midday and afternoon sun, or use a shade cloth to create shade. Water the plant in the morning and evening to keep the soil moist.

Discover information about plant diseases, toxicity, weed control and more.

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Care Guide for Horseweed

Questions About Horseweed

More Questions People Also Ask

More About How-Tos

Common Pests & Diseases

Weed Control

Distribution Map

Habitat

More Info

Name story

Symbolism

Usages

Scientific Classification

Related Plants

Related Articles

Care Guide for Horseweed

Questions About Horseweed

More Questions People Also Ask

More About How-Tos

Common Pests & Diseases

Weed Control

Distribution Map

Habitat

Map

More Info

Name story

Symbolism

Usages

Scientific Classification

Related Plants

Related Articles