Question: It seems like a lot of trouble and expense to germinate herb seeds under lights. How hard is it? Is it worth it?
Answer: If you want just one or two plants or if you’re after a cultivar that doesn’t come true from seed, buy them. If you want to fill in a large area in the garden, or if you want varieties that you can’t find at your local nursery, or if you want to save money, consider setting up grow-lights in an out-of-the-way spot in the house. Over time, they will more than pay for themselves.
A basement is an ideal spot for a grow-light setup because the cooler temperatures there (60° to 65°F) promote sturdy, steady growth of many kinds of young plants. A spare bedroom, a garage that isn’t too cold, or even a closet are other possible locations. My grow-lights, inexpensive shop fixtures available at any hardware store, are 4 feet long with double fluorescent tubes and are suspended on chains that let me raise the height of the lights as the plants grow. Adjustability is crucial to success. An inexpensive timer turns the lights on for sixteen hours, then off for eight, freeing me from having to remember to do it myself.
Before you purchase lights, decide which kinds of seeds you want to sow so you can buy the right amount. To find out how many weeks each type will take to grow to transplanting size, consult the seed packet or a good reference such as New Seed-Starters Handbook, by Nancy Bubel (Rodale Press, 1988), then count back from your average frost-free date to determine when to sow them. Call your county extension service if you’re not sure of the frost-free date in your region.
Some seeds need special treatment to help them germinate, such as soaking in water overnight or nicking the hard seed covering. Some need light to sprout, so they’re sown on or just below the surface of the potting mix. Others need to be kept dark–cover the pot with brown paper but remove it after sprouts begin popping up.
Fill a clean flat (or individual pots that have holes for drainage) with slightly moist potting mix, sow the seeds (sparingly!), and cover them lightly with more potting mix (or not, if they need light to germinate), firming it with your fingertips. Water thoroughly, taking care not to dislodge the seeds.
Seeds need warmth and moisture to germinate. Set the flat in a warm spot and keep the potting mix evenly moist. Because the air in my house tends to be dry, I keep a mister nearby and spritz the flat several times a day. As soon as you see the first little green sprouts emerging, move the flat under the lights. Position the lights as close to the plants as you can without touching the leaves. If the lights are too far away, the plants grow slowly and get leggy. For fast-growing plants, you may need to raise the lights every few days. (Place flats of slower-growing plants on slabs of wood or other props to keep their leaves close to the lights if you don’t have a separate fixture for them.) Feed the plants regularly with a dilute solution of a soluble all-purpose fertilizer, following instructions on the package. Thin out the seedlings by clipping off extras at soil level rather than pulling them out and disturbing the roots of the ones you want to keep. Water only as needed to keep the soil moist. As the plants grow, they’ll begin using water more rapidly than they did when they were tiny.
When the seedlings have their first sets of true leaves (they’ll look different from the plants’ first, seed leaves), fork them gently out of the flat and transplant them into individual pots. I use recycled 21/2-inch-square plastic pots, which I’ve washed with a detergent and bleach solution to prevent disease, and I line them up in shallow trays to catch any water that may come out of the drain holes. You’ll know a plant has outgrown its current pot when roots start growing out the hole in the bottom.
Allow at least a week of gradually increasing exposure to outdoor conditions (start with an hour in the shade in a protected spot) to harden off the plants before planting them in the garden.
Kathleen Halloran is a freelance writer and gardener in LaPorte, Colorado.