Lack of light is the number one killer of indoor plants behind too little or too much watering. If your plants don't have enough light they will grow slowly and could even die.
For young seedlings, light is particularly important. With too little light, new sprouts will become stretched (leggy) and fall over. Seedlings should be moved to light immediately after they sprout.
It's a good idea to experiment with different locations for your plants to find the best lighting conditions.
Indoor Lighting Considerations
- Duration. The hours of light per day.
- Intensity. The brightness of the light.
- Coverage. The distance of the light to the plant.
Each component is important to ensure your plant has enough light to thrive.
There are two ways your plant will get light indoors: from the sun or from grow lights.
Most plants prefer placement near a clean, unobstructed, brightly lit south-facing window with at least 6-8 hours of sunlight per day.
Ensure outdoor temperatures are consistently above 55-60°F as a cold windowsill can prevent or slow growth. Avoid drastic temperature changes.
With sunlight, the duration of light available is always the same every day. However, depending on the season and latitude the hours available every day will change.
More light is available in the spring and summer than in fall and winter. In the Northern Hemisphere, higher latitudes have less light per day than lower latitudes.
While the intensity of solar output is constant, obstructions and the time of day affect how much light reaches your plant. The most intense light is directly in front of a clean, unobstructed window.
Dirty windows, other plants and trees, buildings, and any other number of things can affect the intensity of light that reaches your plant's leaves.
Peak light intensity, depending on which direction your window is facing, is typically highest during the middle of the day.
The direction of your windows plays a critical role in how much light your plants receive. A south facing window is best (in the Northern Hemisphere), though an east or west facing window can work too.
- South-facing: Provides the most light. Plants can be placed far from the window and still receive bright light.
- East-facing: Much less light than south-facing. Plants can be placed a few feet from the window, but not much further.
- West-facing: Same as east-facing, but transmits more heat. Use a sheer curtain during the middle of the day.
- North-facing: Provides the least light. Plants must be placed directly in front of the window for any amount of light.
While indoor plants typically don't have a problem with too much sunlight, if your plant is wilting, and you're keeping it watered, try moving it a few feet from the window or put up a sheer curtain during the middle of the day.
Grow lights are specially designed light bulbs for growing plants that can be used anywhere. The most cost effective and energy efficient options are T5 fluorescent (get a 6500 K bulb) or LED grow lights (get a blue or full spectrum for vegetative growing).
By using a timer, grow lights can be controlled to turn on and off at specific times. This is incredibly helpful. The lights should be on for 12-18 hours per day, with the ideal duration closer to 16-18 hours per day for the fastest growth.
Don't leave them on 24 hours per day - give your plants a chance to rest.
Most lights designated as "grow lights" will be bright enough to grow a plant. However, there are exceptions.
T5 fluorescent lights are an excellent, energy efficient, and cost effective option. While 1 bulb can work, 2 or more is ideal - particularly when that's the only source of light for your plant. T5 bulbs typically come in 2-4 ft lengths so plan your layout accordingly. Make sure to get a bulb rated at 6500 K.
Even more energy efficient than T5 lights, LED grow lights may give off a purple or pink glow. This is normal as part of their incredible efficiency - plants prefer certain wavelengths of light so the LED emits only what it needs to. Make sure the light is at least 7-15 watts for adequate output. Very cheap options should be avoided as their actual output may not match the advertised wattage. For growing herbs or greens, get a blue or full spectrum LED system. For flowering plants (tomato, etc.), get a red spectrum.
Because the output of grow lights is less than that that of the sun (good thing too), the lights need to be kept close to the plant's leaves.
As the plants grow, simply adjust the grow lights up. Keep T5 grow lights 3-6 inches from the leaves. LED lights should be kept 8-12 inches away from plants.
If the leaves start to turn brown and crispy on the tips near the light, they may be getting burned - move the lights a bit further away.
That's it! Now all you have to do now is select the best lighting option for you - then your indoor garden will be lit!
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