A Guide to Giving Your Houseplants the Perfect Sunlight

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Monitoring the lighting needs of houseplants can be a challenge. Here’s a guide to getting it right, no matter the time of year. Read on to learn how to gauge indoor light intensity and make changes for healthier plants.

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Every plant grower knows that light is critical for healthy houseplants. Without it, your plants will wither and never reach their full potential. However, determining precisely how much light each plant needs can be challenging, and you may feel limited by what’s naturally available in your space.

A Guide to Giving Your Houseplants the Perfect Sunlight

Light, whether natural or artificial, provides plants with the energy they need to photosynthesize. While lighting requirements vary by variety, all species need a minimum light exposure to continue growing.

The key to healthy indoor plants is determining how much light they need and modifying your space to accommodate those requirements. Unsure where to start? Here’s what you need to know.

A Guide to Giving Your Houseplants the Perfect Sunlight
More or Less Light?

It can be challenging to determine whether your plants require more or less light exposure. Some signs that your place has too much light exposure include:

In contrast, slow, leggy growth is a sign that plants are struggling to get enough light and need more direct exposure.

A Guide to Giving Your Houseplants the Perfect Sunlight
Understanding Indoor Lighting Needs

Growing plants indoors is a far different process than outside. Even the brightest window lets in only a fraction of light compared to being outside.

As a general rule, expect to lose up to 50% of the light intensity even just one meter away from the window. But even so, the window you choose will make a big difference in how much light exposure your houseplant gets.

A Guide to Giving Your Houseplants the Perfect Sunlight
The Importance of Window Orientation

Where your windows are located in the home has a direct effect on the light exposure for your houseplants. Here are the general rules for everyone in the Northern Hemisphere.

A Guide to Giving Your Houseplants the Perfect Sunlight
A Guide to Giving Your Houseplants the Perfect Sunlight
How to Measure Light Intensity

The intensity of light is measured in units known as foot candles (ftc). As a way of explanation, one foot candle is the approximate brightness of a single candle placed one foot away.

Outdoor light is exceptionally bright compared to indoors. Even in the middle of winter, outdoor brightness easily reaches over 400 ftc. In contrast, north-facing windows might not ever get over 40 ftc.

A Guide to Giving Your Houseplants the Perfect Sunlight

What do these terms mean for light intensity? Here’s a primer on different indoor light intensities:

A Guide to Giving Your Houseplants the Perfect Sunlight

Note that it’s hard to gauge light intensity objectively, as our eyes acclimate to different lighting conditions and will perceive them as more similar than they are.

One way to gauge the lighting is to assess the shadows cast. Sharp, well-defined shadows are signs of bright light, while fuzzy, indistinct shadows indicate moderate light. If shadows are faint or non-existent, then you’re dealing with low light intensity.

A better option is to measure light intensity with professional tools, such as a light meter. Look for the type that will give you a reading in foot-candles or lux (one foot candle is equivalent to about 10 lux). You can also consider using phone apps for a measurement, though these tend only to give estimations.

A Guide to Giving Your Houseplants the Perfect Sunlight
How to Manage Sunlight Intensity

The brightest indoor spaces rarely approach even half the brightness of being outdoors. Even so, it’s possible to burn plants by placing them too close to windows. That’s due to the magnifying effects of the glass, which can concentrate the heat in one direction. For this reason, it’s important to keep plants a few feet away from glass on the brightest days.

You can also dim down the reflective power of windows by covering them with sheer curtains that filter the light.

A Guide to Giving Your Houseplants the Perfect Sunlight

If you want to enhance the light within a room naturally, ensure that walls are painted light colors and place mirrors around the room. Both will reflect light around and boost the ambient brightness within your space. However, the easiest way to increase light intensity is by adding grow lights to the planting space.

Note that light intensity within your home will change throughout the year. Houseplants that thrive in sunny south-facing windows in the summer might need supplemental light to get through the winter months when sunbeams are weaker and angled lower in the sky. Likewise, you may need to move sensitive plants to a more protected space once the summer sun starts to heat your windows.

A Guide to Giving Your Houseplants the Perfect Sunlight

For this reason, it’s important to be flexible with your houseplant placements. For certain varieties to be at their healthiest, they may need to rotate through your home to optimize their light exposure for the time of year.