Published Mar. 15, 2020, in the Wyoming Tribune Eagle, “Better lighting means stronger seedlings”
By Barb Gorges
When hours of daylight are quickly lengthening and seed packets are showing up at garden centers, you know it’s time for flower and vegetable seed starting. If you’ve never tried, it’s time to learn how.
You can go to my archived columns at https://cheyennegardengossip.wordpress.com/ and search “seed starting.” You’ll learn how starting from seed saves you money and gives you options for tomatoes and other vegetables adapted to Cheyenne. Get tips on selecting seeds, potting soil and pots. Learn how to time planting, how deep to plant seeds, how and how much to water and how to avoid damping off. Then learn how to harden off seedlings before transplanting them.
This year I want to talk about light. The right light will give you nice, stocky green plants instead of spindly, sickly ones.
There’s a misconception that windowsills work great for starting vegetable seeds. After all, millions of houseplants can’t be wrong. But houseplant origins are typically the shady understory of tropical forests. Vegetables prefer full sun. Also, many windows are now treated to improve energy efficiency (lowering heat transference) by blocking parts of the spectrum. Greenhouses work better than windows because they give plants direct light from more directions for more hours per day.
Without a greenhouse—glass or hoop house—we’re talking supplemental lighting. On a recent trip to my nearest big box store I found all kinds of grow light bulbs that will fit in a lamp but are not adequate for more than a couple pots. The store also had ordinary 4-foot-long fluorescent shop lights which fit perfectly over two flats of seedlings and will produce decent growth, whether you find full-spectrum bulbs or special grow light bulbs.
But LED lights are taking over. At the same big box store, I found 4-foot LED shop lights. The bulbs are integrated with the fixture and come in a variety of brightnesses, 3,200 to 10,000 lumens, with a range of prices to match, $15 to $75.
There are also LED bulbs, both regular and grow lights, that will replace the bulbs in your T8 or T12 fluorescent fixtures, but they won’t be quite as energy efficient as the integrated ones.
You’ll notice LED bulbs can be about four times more expensive than normal fluorescents, but they cost less than half as much to run and are supposed to last longer.
Then there are the industrial LED grow lights that emphasize blue and red lighting—the important part of the spectrum for growing plants. They come with industrial prices as well. Choosing one gets quite technical. Check out the Colorado cannabis grow suppliers for advice.
However, the few weeks of light our tomato seedlings need hardly justifies industrial lighting.
Because you want to keep the light about a couple inches above the tops of the seedlings, you need to be able to adjust the distance as they grow. Too close and seedlings dry out. Too far and they get spindly. Hang the shop light using the chains that come with it, shortening as needed. Joe Lamp’l, host of PBS’s Growing a Greener World, suggests using ratchet pulleys instead.
Or, rather than move the light, you can stack boxes under the flats to bring them up to the light and remove the boxes to adjust the distance as the plants grow.
How do you hang the shop light? You can hang it from the ceiling over a table, especially somewhere like an unfinished basement room.
A set of adjustable utility shelves works well if there is a way you can attach your light fixtures to the underside of the shelves and adjust them. Keep in mind the distance between shelves must accommodate seedling height at six or eight weeks plus a couple inches of space and the light fixture thickness.
Mark and I put freestanding utility shelves in our unused bathtub. For the top shelf we put an expandable shower curtain rod over it and hang the shop light from it.
Plugging it in
Some shop lights can be strung together. Otherwise, if you have multiple lights, you are looking at a power strip, giving you a handy way to flip them off at once. Or, plug the power strip into a timer. Lamp’l’s latest home research shows 16 hours of light per day is about right—seedlings need to sleep too.
Mark and I use electric heat mats under the flats and clear plastic domes or plastic wrap over them to keep the moisture in. But at the first sign of seed germination, they should both be removed.