Starting Seeds Indoors | Seed-Starting in Winter

Although it is still winter in New England, it’s already time to begin preparing for the coming gardening season. Even while the ground is frozen and covered in snow, we can be starting seeds indoors and giving them a head start to ensure that they reach their full potential during peak growing season.

Starting Seeds Indoors in Winter

Starting seeds indoors — where the environment is a little friendlier than the wintry landscape outside — is a great way to get your plants primed and ready for life outdoors. In fact, some plants should even be started as early as February! Peppers are probably the best example of a vegetable that should be sown indoors before spring. Pepper seeds commonly take between ten days and three weeks to germinate, depending on the temperature of the soil. The plants grow slowly at first, although growth rate is also temperature-dependent. Since the growing season is relatively short in the Northeast, many want their pepper plants to be over eight inches tall by the time they plant them outside in late May. A larger pepper plant will bear more fruit over the season, so an early start is desirable.

Using a Seed-Starting Soil Mix

Whether you’re growing peppers or other plants, it’s a good idea to buy new seed-starting mix from the garden center. “Why do I have to use a special seed-starting mix?” a woman at my seed-starting class asked me. “When my father started seeds up in Maine, he just scooped some dirt out of the garden and put it in an old wooden box.” This was a typical question asked during my class, so I’ll give several good reasons for using a soil mix made specifically for seed-starting.

The first argument for using a seed-starting mix is that it can hold moisture evenly as seeds germinate. Seed-starting mixes are primarily made up of peat moss and vermiculite, and this mix retains water longer than soil from the garden. Secondly, these media are weed free, so you’ll be sure that the tiny plants that emerge from it are actually what you intended to cultivate. Studies show that when a planting medium contains peat moss, germination rates are better, which is the third reason to use such a seed-starting mix. And finally, a new bag of seed starter doesn’t contain the range of fungi that outdoor dirt does, which can cause something known as “damping off.”

What is Damping Off?

“Did your father ever complain about damping off?” I asked the woman whose father had used garden soil. “Oh yes, all the time,” she answered. Damping off is the term for a fungal problem that sometimes plagues people who germinate seeds indoors. There are at least three types of fungi that cause this condition, and they make young seedlings suddenly collapse where their stems meet the soil. One day you can have a flat of young, eager seedlings, and the next day they are prostrate and wilted on top of the dirt. Once seedlings succumb to damping off, there is no cure, so using a seed-starting mix without errant fungi gives your plants a better chance at thriving. As I discussed this fungal problem in class, someone asked about sterilizing garden soil. I agreed that if soil is baked in a hot oven for long enough it will kill both weed seeds and fungi, but such heat also kills beneficial microorganisms. I finished with the final reason you might not want to bake your garden dirt, and this is one I know from experience: “Do you know how baking dirt smells?” I asked them. “It isn’t exactly potpourri…”

Tips for Successful Seed-Starting:

• Get the seed-starting mix evenly moist in a tub or bowl before you fill the pots or flats where you’ll plant the seeds. If you don’t have any spare pots or flats, make a mini greenhouse to start your seeds in.

• Read the seed packets carefully for instructions on the best planting times and methods of germination. Some plants, such as zinnias and tomatoes, grow fairly quickly, while others take more time. Some seeds germinate better when exposed to light and others do best when covered with a thin later of soil. Most seed packets will either list this information on the back or will point you toward a website where it can be found.

• After the seeds are sown, cover the pots or flats with clear plastic that will stay in place until you see the green seedlings emerge. Check the flats daily. Moist seed-starting mix will hold the right degree of moisture for up to three weeks when covered by plastic.

• If you don’t have a very bright window for young plants, grow them under lights. Keep common fluorescent bulbs 3-5 inches above the plants.

• Don’t overwater. When the seedlings are small, they won’t need as much moisture. Once they are larger, water as the soil mix dries. Transplant larger seedlings into bigger pots as they grow.

With this advice in mind, starting seeds indoors should be a breeze. Do you start your seeds indoors each winter? This post was first published in 2017 and has been updated. 

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