Emma Erler, host of Homegrown NH and lead horticulturist with Kirkwood Gardens, says New Hampshire gardeners can finally get their hands in the soil!
She starts her pepper seeds in early March, due to their long germination period. It’s just one of some 600 plants she gets started under grow lights this month.
With her experience, she has some recommendations for using grow lights to jumpstart your garden by starting seeds indoors.
Erler sets up her seed-starting operation in an out-of-the-way spot, away from heavy traffic, pets, cold drafts, and excess heat. Spills will happen, she says, whether it’s potting mix, water, or fertilizer, so you want to set up in a spot where this isn’t a problem. The air temperature must be consistently above 60F.
“Avoid the windowsill,” she says. “It’s the coldest place in the house, especially at night, and cooler soil temperatures can lead to seedling death due to disease.”
Window-sill grown plants tend to be too tall, with thin, bent stems.
Erler says it’s better to grow seedlings under fluorescent or LED lights than to rely solely on natural light (unless you are lucky enough to have a greenhouse).
Lack of light is the major cause of elongated, skinny stems. You can find lights that are sold specifically as “grow lights,” designed to provide light in the specific ranges required by plants. But you can also use the less expensive standard fixtures with two cool white fluorescent tubes in each.
The lights need to be no more than 4 inches above the tops of seedlings, although 2 inches is ideal. As the plants grow, you will have to be able to raise the lights, so Erler suggests hanging the lights from chains to make it easier.
Plants need 12 to 16 hours of light daily. But you can’t leave lights on continuously, as many plants need a dark period each night to develop properly. Erler suggests a simple timer as part of the set-up so lights are turned off and on automatically.
Erler uses electric heat mats to provide gentle heat from underneath, which is especially helpful in the uneven heat of drafty New England homes. It prevents damping off, and encourages faster germination and healthier roots.
Erler says the germinating seeds benefit from constant heat while they’re germinating, so she doesn’t plug the heat mats into the timer for the lights. Electric heat mats specifically for seed starting can withstand moisture. They are available from many garden centers and online suppliers.
Start seeds in small, individual containers, such as cell flats or small individual plastic pots with drainage holes. If you’re reusing containers, sterilize them in a 10% bleach solution for 30 minutes.
Fiber or newspaper pots can be a good option for plants that don’t transplant well, like squashes, with the caveat that these will dry out faster than other materials. Trays with clear plastic dome lids allow light in and keep moisture from escaping and trap heat.
Erler recommends using a commercial, sterile, seed-starting mix composed of peat, perlite, vermiculite, or coir to get your seeds started.
See you in the garden!
Homegrown New Hampshire is a collaboration between Squam Lakes Natural Science Center and NHPR.
