When watering the Common mullein, you should aim to use filtered water that is at room temperature. Filtered water is better for this plant, as tap water can contain particles that are harmful to its health. The reason that the water should be at room temperature or slightly warmer is that the Common mullein comes from a warm environment, and cold water can be somewhat of a shock to its system. Also, you should avoid overhead watering for this plant, as it can cause foliage complications. Instead, simply apply your filtered room temperature water to the soil until the soil is entirely soaked. Soaking the soil can be very beneficial for this plant as it moistens the roots and helps them continue to spread through the soil and collect the nutrients they need.

Both overwatering and underwatering will be detrimental to the health of your Common mullein, but overwatering is a far more common issue. When this species receives too much water, its stems and leaves may begin to wilt and turn from green to yellow. Overwatering over a prolonged period may also lead to diseases such as root rot, mold, and mildew, all of which can kill your plant. Underwatering is far less common for the Common mullein, as this plant has decent drought tolerance. However, underwatering remains a possibility, and when it occurs, you can expect to find that the leaves of your Common mullein have become brittle and brown.

It is crucial that you notice the signs of overwatering as soon as possible when caring for your Common mullein. Some of the diseases that arise from overwatering, such as root rot, may not be correctable if you wait too long. If you see early signs of overwatering, you should reduce your watering schedule immediately. You may also want to assess the quality of soil in which your Common mullein grows. If you find that the soil drains very poorly, you should replace it immediately with a loose, well-draining potting mix. On the other hand, if you find signs that your Common mullein is receiving too little water, all you need to do is water more regularly until those signs have subsided.

If your plant is in a pot. The most precise way to decide whether your Common mullein needs water is to plunge your finger into the soil. If you notice that the first two to three inches of soil have become dry, it is time to add some water.

If you grow your Common mullein outdoors in the ground, you can use a similar method to test the soil. Again, when you find that the first few inches of soil have dried out, it is time to add water. During the spring and early fall, this method will often lead you to water this plant about once every week. When extremely hot weather arrives, you may need to increase your watering frequency to about twice or more per week. With that said, mature, well-established the Common mullein can show an admirable ability to withstand drought.

When it comes time to water your Common mullein, you should not be shy about how much water you give. With the first two to three inches of soil dry, this plant will appreciate a long and thorough watering. Supply enough water to soak the soil entirely. The amount of water you add should be enough to cause excess water to flow through the drainage holes at the bottom of your pot. If you don’t see excess water draining from the pot, you have likely underwatered your plant. But do not let the water accumulate inside the soil, which will be very dangerous to the plant as well. Alternatively, a lack of water draining through the pot could indicate poorly draining soils, which is detrimental to the health of this plant and should be avoided. If the plant is outside, 1 inch of rain per week will be sufficient.

The water needs of the Common mullein can change depending on growth stages as well. For example, when your Common mullein is in the first few years of its life, or if you have just transplanted it to a new growing location, you will need to give more water than usual. During both of those stages, your Common mullein will put a lot of energy towards sprouting new roots that will then support future growth. For those roots to perform their best, they need a bit more moisture than they would at a more mature phase. After a few seasons, your Common mullein will need much less water. Another growth stage in which this plant may need more water is during the bloom period. Flower development can make use of a significant amount of moisture, which is why you might need to give your Common mullein more water at this time.

The Common mullein will have its highest water needs during the hottest months of the year. During the height of summer, you may need to give this plant water more than once per week, depending on how fast the soil dries out. The opposite is true during the winter. In winter, your plant will enter a dormant phase, in which it will need far less water than usual. In fact, you may not need to water this plant at all during the winter months. However, if you do water during winter, you should not do so more than about once per month. Watering too much at this time will make it more likely that your Common mullein will contract a disease.

It is most common to grow the Common mullein indoors for any gardener that does not live in temperate and tropical regions. Those gardeners should consider the fact that soil in a container can dry out a bit faster than ground soil. Also, the presence of drying elements such as air conditioning units can cause your Common mullein to need water on a more frequent basis as well. if you planted it outside. When that is the case, it’s likely you won’t need to water your Common mullein very much at all. If you receive rainfall on a regular basis, that may be enough to keep your plant alive. Alternatively, those who grow this plant inside will need to water it more often, as allowing rainwater to soak the soil will not be an option.

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 Common mullein 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.

The Common mullein 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 Common mullein is always exposed to the sun.

When the temperature rises above 90℉(32℃), the Common mullein 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 Common mullein 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 Common mullein is still drooping, this means that the plant is losing water fast, and you need to water them.

The Common mullein 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 Common mullein 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.

When the Common mullein 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 Common mullein 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.

When the Common mullein 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.

During summer or late spring, the Common mullein needs 6 to 8 hours of direct light every single day. This is whether they are planted outdoors. If the Common mullein 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.

When transplanting the plants, they should not be exposed to sudden sunlight. Give the Common mullein 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 Common mullein 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.

The best temperature for Common mullein 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 Common mullein 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 Common mullein may be able to survive with some help.

During the warmer parts of the year, Common mullein 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 Common mullein. Hotter temperatures can cause wilting, drooping, and even sunburn on the leaves, which can be difficult for Common mullein to recover from. There are quite a few ways to combat this issue that are quick and easy!

If this is the first year of your Common mullein 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 Common mullein, 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 Common mullein 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 Common mullein 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 Common mullein 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.

If cold temperatures (below 15℉(-10℃)) do occur during the growing season, there are a few measures you can take to help protect Common mullein from frost or cold damage. If you’re growing Common mullein 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 Common mullein 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 Common mullein 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.

During the cold winter months, Common mullein 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 Common mullein, 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 Common mullein. 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, Common mullein will be able to resprout at the correct time without any help, but this method increases the chances of a successful second sprouting.