The true measure of any home gardener is their first tomato. Not just any tomato, but one of those giant heirloom slicers, which they will display with smug self satisfaction over social media. The earlier in the summer, the better, which leads gardeners to do all kinds of wacky things to get bigger plants in the ground sooner. We’ve constructed temporary greenhouses and moved heaters into our tomato beds—anything to get a tomato sooner in the year.
To complicate matters, each year our tomatoes do unpredictable things. A consistent variety will suddenly perform differently, or the seeds won’t take. There is one perfect way to solve both of these issues: Preserve your favorite tomatoes and get them earlier in the season next year by overwintering them.
You won’t be producing tomatoes over the winter—that requires a greenhouse or a lot of plant lights and manual pollination, and it risks bringing a lot of bugs into the house. Instead, you’ll be sending these plants into hibernation.
Experienced tomato gardeners chop their plants back starting in late July to prevent more flowers and tomatoes from starting that won’t have time to ripen by fall. Harsh, but necessary. Ideally, you’ll have time for your tomatoes to ripen before you get consistent 40°F at night, but if you don’t have time, either concede that you’ll be eating fried green tomatoes or try to cut off a fair amount of branch with the tomato and hang it upside down inside to ripen. If the tomato has any blush whatsoever, it’ll likely ripen on its own, without the branch, inside.
How to overwinter tomato plants
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There are a variety of ways to overwinter tomatoes, and one of the most popular is to take a cutting from your favorite tomato plant and reroot it over the winter. Since tomato stems are highly rootable, this is an easy way to start next year with a decent sized tomato plant, assuming your cutting makes it through winter. However, since you are bringing a branch with leaves indoors, you are also possibly bringing in bugs, so I defer to a less popular method—bare root overwintering.
Much like you do with peppers, this method involves pruning your tomato plant all the way back to a main stem and a few nodes. You’ll trim off all leaves. Dig generously around the plant with your garden spade, since tomatoes tend to have prodigious roots. Once you’ve freed your tomato plant, you’ll remove the dirt from all the roots, carefully using your fingers. Trim the roots to twelve inches or so, and then it’s time to dip.
Prepare a bucket of water and neem oil and castile soap. Fill a five-gallon bucket about halfway with water. Add a teaspoon of castile soap and the same amount of neem oil and stir. Think of this like a flea dip: Make sure you get all the roots, and use the water to really get rid of any dirt still hanging onto them. Allow it to sit for a minute to soak before flipping it upside down and doing the same to the stem.
How to store tomato plants for winter
You can take two different approaches to storing your tomatoes. The first is to keep the plant bareroot, carefully wrapping the roots in some damp newspaper and fabric, securing it with twine, and then leaving it in your fridge or another suitably cold—but not freezing—location for winter. You want them to remain above 40°F but below 60°F.
Frankly, I have a small fridge, so I have always gone the other way, which is to root them in a gallon-sized pot. Take an eight-inch pot, and place some moistened potting soil in the bottom, filling up an inch or two. Carefully spread out the roots of the tomato plant on the soil, and use your fingers to add soil between the roots. Continue filling the pot with soil, and because they’re tomatoes, it’s OK to cover up some portion of the stem with soil. You’ll want to expose the nodes, so I leave an inch or two below the first branch above the soil line.
Now give the plant a light water, and place it someplace it can get ambient light for three hours or so a day. If a window isn’t an option, a plant light will work. Make sure you water the tomato once every two weeks or so, but it won’t need fertilizer or heavy watering. Prune leaves as they come in and watch for bugs. If you see any, isolate the plant and treat with neem oil.
How to harden your tomatoes come spring
In late winter, you can start allowing the tomato to grow again. Start ramping up the amount of light each day, and add fish fertilizer to the water. Your tomato plant should start growing again.
If you overwintered in the refrigerator, late winter is a good time to plant the root inside following the above directions. Give it a day or two to recover before you begin exposing it to light, and then slowly introduce it. Treat these tomatoes as you would one of your up-potted seedlings.
Harden it to the outdoors as you would your other seedlings, and ensure when you plant it, you dig a hole three times the size of the pot, into a hole with slow release fertilizer, bone meal, and nitrogen fertilizer. Your tomatoes should come back with fruit earlier by being an already mature plant.