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Growing tomatoes and peppers in central Ohio can be a bit challenging. With an annual average of only 150 days between the last spring and the first fall frost, there isn’t much time to get a long harvest period from crops that thrive in warm weather. Most of the larger-sized slicing tomatoes take an average of 80 or more days to mature, meaning that from the time you plant a seed to the first ripe tomato will take three full months!
We work hard to get an early start on that three months to have large tomatoes earlier. Beginning in early March, we seed flats of tomatoes in 72-cell growing trays. To get tomatoes to germinate in the coolness of our basement, the trays sit on temperature-controlled heat mats and are covered with humidity domes. After about six days at 75 degrees, the seedlings emerge, ready to move over to the light shelves. We use 4 ft long wire shelving with pink LED grow lights suspended over each shelf. The lights are controlled with a timer to allow the plants a 12-hour on/off photoperiod. After about three weeks in the trays, the seedlings are ready to be “potted up” into larger pots. The seedlings’ roots are quickly expanding, and we find that 3.5 to 4-inch square pots give the plants enough room while maintaining efficient use of space under the lights.
After about another 3 to 4 weeks, the seedlings are 6 to 8 inches tall and are ready to be hardened off. Hardening off is the process of acclimating the plants to outside conditions. To harden off young plants, we transfer them to benches in our polycarbonate propagation greenhouse. By opening the vents in the roof of the propagation greenhouse, the seedlings are exposed to breezes and stronger sunlight, which quickly strengthens them and causes them to ramp up their growth rate. If you don’t have a shelter like a greenhouse to harden off your seedlings, simply allowing them to hang out on the porch for a few hours each day will also help them adjust to outside growing conditions. Bring them inside each night since overnight temps in Ohio can fluctuate quite a bit, and you don’t want to shock your plants.
After a week of careful observation, watering, and monitoring the plants’ response to being outside, it’s usually safe to plant them in their final spot. For us, tomatoes, peppers, and cucumbers grow inside one of two high tunnels we have on our farm. The high tunnels do a great job of controlling the rainfall that gets on the plants (like, none!) and also help us control the air temperature. Tomatoes and peppers love the heat and will not produce well if the temperature drops below 50 degrees. Studies show that even though tomatoes can survive temperatures below 50, exposure to low temps can permanently stunt their potential production of fruits.
So there you have it, our method of starting seedlings under lights to produce better and earlier tomatoes, cucumbers, and peppers. We hope this helps you get a start on your summer garden plans. There’s nothing in a store that compares to a homegrown tomato!