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Is my window bright enough?

by Timber Press on June 25, 2018

in Gardening

My window is bright enough, right? New indoor growers ask this hopeful question all too frequently, and it often leads to disappointment.

While many books and websites insist that you need only a bright window to get your tomato seeds going or your orchids reblooming, this approach is rarely satisfying.

Ambient light levels inside your home are significantly lower in intensity and ultimately different in spectrum than natural outdoor light, especially during the winter months. Even a seemingly bright window may not provide enough light, or the right kind, for young seedlings or fruit-producing plants. Have you ever started seeds indoors in a sunny window, only to watch the tiny seedlings lean so far that they topple over? Perhaps you’ve tried some beautiful succulents and watched them do the same.

Your plants are starving for, and stretching toward, the light.

There are plenty of low-light tropicals and blooming plants that you can grow successfully indoors with good ambient light, and you can maintain certain light-loving succulents for a while in a windowsill. But even a bright windowsill is typically not the right location for plants you intend to harvest for food. The same goes for heavy-blooming plants. Reproduction is an energy-intensive process. Producing flowers, fruit, and seed requires a lot of juice. Plants need enough light, and the right kind of light, to get the job done.

You may have learned that in your outdoor garden, plants that produce large fruit, such as tomatoes, require roughly double the duration and intensity of direct sunlight as plants that produce mostly foliage, such as leafy greens and lettuce.

A plant’s heritage—that is, the geographical area where it naturally evolved—dictates its requirements for specific light intensity, duration, and spectrum to reproduce successfully. If you are going to invest time, effort, and money in indoor growing, quality supplemental lighting should be your number-one priority.

If you already garden outside, growing plants indoors under lights is a great way to supplement your efforts and extend your seasons and yields. If gardening indoors is your only option, grow lighting can transform your living and eating experiences and bring some much-needed nature into your home.


Leslie F. Halleck is a dedicated horticulturist with a master’s in horticulture from Michigan State University. She is a Certified Professional Horticulturist (CPH) via The American Society for Horticulture Science, with more than 25 years of green industry experience in research, greenhouse production, public gardens, garden center retail, landscape and design services, and gardening communications. She currently runs Halleck Horticultural, LLC, a company that provides consulting services to green industry businesses, as well as horticultural consulting.

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