If you’re a gardener, thoughts turn to germinating tomato (Lycopersicon esculentum) seeds when January rolls around, because tomatoes can be started from seed indoors about six to eight weeks before the last frost date. As noted by North Carolina State University, tomato seeds germinate with or without light, so there’s no need to place them in a sunny window, but, once seeds sprout, they do need lots of light to grow and become vigorous.
Since seeds don’t need light to germinate, you can germinate them anywhere, even inside a dark cabinet if you like. Start seeds by sterilizing a seed tray by soaking it for 10 minutes in a solution of 1 cup bleach and 9 cups water. Thoroughly rinse and dry the tray before filling it with seed-starting mix that contains fertilizer, available from garden centers. Fill to within 1/4 inch from the lip, tamp the soil down slightly to remove air pockets. Water the mix so it’s wet all the way through, but not soggy. Sow the seeds by poking a hole in each tray cell, with your finger, 1/4-inch deep into the soil. Drop in one seed per hole and cover with enough soil so it’s level. Add enough water to moisten the seed and added soil, and replace the tray’s plastic cover to prevent moisture loss.
Keeping Seeds Warm
For seeds to germinate, the soil needs to be kept between 70 and 80 degrees Fahrenheit. You can place them in a warm location in your house or place the tray on a heat mat. A heat mat keeps soil at about 70 degrees Fahrenheit. Generally, seeds germinate in seven to 10 days. While you’re waiting for the seeds to sprout, keep the soil moist. Use your finger to see if the top 1/4 inch is dry, if so, add enough water to moisten the soil. Don’t overwater. Soggy seeds rot and won’t germinate.
Once seeds have sprouted, seedlings prefer temperatures around 65 F. You can place them in a south-facing window, but because sunlight in winter is not as intense as in summer, tomato sprouts may grow into spindly, weak seedlings if only given natural light. The University of California Cooperative Extension explains that you can strengthen seedlings by providing bright light for an additional three or four hours a day, for a total of 16 to 18 hours of light per day. Place newly sprouted seeds under two 40-watt fluorescent bulbs hung about 4 inches above the plants, or some other kind of grow light. Don’t use incandescent light bulbs as they are hot and scorch plants. As the plants grow, adjust the bulbs upward. Plants also need a period of dark, so turn off the lights each evening. Don’t grow seedlings on a heat mat, and continue to water them when the soil mix dries out. Supplemental fertilizer is not needed until the seedlings are transplanted outdoors.
Transplanting Spindly Seedlings
If you do try growing tomato seedlings in a sunny window and the plants become leggy and weak, don’t despair. Just plant them in the ground deeper than you would normally, at a 45-degree angle with only the top two or three sets of leaves sticking out. Before planting, remove the lower leaves from the stem of the tomato plant. Cover the seedling so the soil is level. Water thoroughly and in time new roots will form along the stem, where you removed the leaves, creating a healthy, vigorous plant.
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