Starting Seeds: Light

If you’ve ever tried growing seeds indoors, you may have ended up with tall and spindly plants, flopping over, adorned with pale leaves. When planted outside, these ungainly wisps quickly succumb to bright sunlight and the gentlest of breezes. What’s a gardener to do?

While overabundant food and water, coupled with too-warm temperatures, contribute to this problem, the primary culprit is insufficient light.

The crops most commonly grown in our veggie gardens all require full sun—at least eight hours per day. Likewise, bright light is essential for producing stocky seedlings with healthy green leaves.

Many gardeners successfully start their seeds on a sunny windowsill. While readily available in most homes, this is actually the more difficult route to take. All that sun pouring through the glass also provides plenty of heat—more than enough to fry tiny seedlings. Then at night, the windowsill becomes much colder than the rest of the room. Leaves that actually touch the glass may freeze. These temperature extremes are a significant problem. Keeping your seedlings a few inches away from the window helps, but leads to yet another problem.

Light from a window comes from only one direction. Your tiny veggies, in their efforts to receive enough light for healthy growth, will tend to grow toward that light. The result is that familiar row of spindly plants, bending toward the sun. Rotating the pots helps, but it doesn’t really solve the issue. Finding the exact balance between light intensity and temperature fluctuations is difficult, and sometimes impossible.

With some investment in light fixtures, bulbs, and space, you can provide a much better alternative. I’ve been raising my transplants under artificial light sources for many years.

plant-lights-lahTo start, you need a couple of 4-foot fluorescent light fixtures for each two trays of seedlings. They don’t need to be fancy, unless you are concerned with appearance. Shop lights work fine. Fit them with 40 watt light tubes. There are various plant lights on the market, all at increased cost. Save your money. Specialized bulbs are not necessary if all you are doing is raising seedlings to transplant size. Some newer energy-saving bulbs have less wattage. If they produce the same number of lumens, they’ll work just as well. The key is light intensity.

Now decide how you will suspend your fixtures over your plant trays. My husband built a stand for me that holds six fixtures, enabling me to start six trays of seeds at one time. You can hang the lights from the ceiling, prop them up on blocks, or screw them to the bottom of a bookcase shelf. You will need enough space to raise the light bulbs (or lower the trays) as the plants grow.

light-timer-003rsA timer isn’t essential, but it will make your life easier. Set it so that the seedlings receive 14 – 16 hours of light per day. (If you are growing lettuce of spinach seedlings, keep their “days” to 14 hours or less, or they will try to flower and set seed instead of producing a crop.)

Set your planted trays under the lights. You want them as close as possible to the bulbs without having them actually touching. Be careful not to catch the labels on the light bulbs.( I can’t tell you how many carefully planted pots have had to be redone because I forgot that the labels were sticking up taller than the trays.)

The fluorescent lights provide just the right amount of warmth to speed germination, but are cool enough to be safe for the plants. I’ve even started trays by placing them on top of the light fixtures, to take advantage of the heat. Of course, once the seeds germinate, I have to move them where the light shines on the tiny sprouts.

Keep the lights as close as possible as the plants grow. If your lights are suspended on chains, you can just raise them link by link. I find it easier to raise and lower the seed trays, which I accomplish with a pile of wood pieces cut into varying thicknesses.

The growing seedlings can stay under these lights until it is time to begin hardening them off for planting into the garden.

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