Protecting Tomatoes from Frost: How to Save Tomato Plants from Winter’s Grasp

Tomatoes are very sensitive warm-weather plants.

They don’t like the cold at all, and they succumb to frost quite easily.

If you’re preparing for some upcoming winter weather or a late spring freeze, try these tricks to keep your tomato plants safe while enduring low temperatures.

You can’t revive a tomato plant that has completely died back from a freeze, but you can protect them from the cold and save cold damaged tomato plants!

Are You Maintaining a Fall Garden, or a Spring Garden?

First, we need to know whether you’re maintaining mature plants in the fall to extend the current year’s harvest, or protecting early seedlings to get a jump start on spring planting and early summer harvests. Your USDA growing zone will help you to determine first and last average frost dates, allowing you to plan planting and harvest around these dates.

Since there is a drastic difference in plant size, methods will vary. First, we’ll start with the mature tomato plants in a fall garden.

Keeping Tomatoes Alive in Autumn: Fighting the Frost

If you’re bracing your garden for the cold weather, you know that your tomato, squash, and melon plants are among the first to go. Whether you’re in a location with a short growing season attempting to get a decent tomato harvest, or a southerner who wants to keep fresh tomatoes alive for as long as possible, there are ways to extend the harvest into late fall and even winter.

The Bucket Method

During the summer, be sure to plant a few tomato plants in 5 gallon buckets. This way, you can move the bucket into a protected area during colder nights. This can extend your harvest by several weeks, giving you fresh tomatoes for far longer than the ground will! Many people will move the buckets inside, allowing the tomato plants to stay 60*F or warmer.

Sheets and Cloth for Frost Protection

If you have some sheets that are solely for protecting the garden, toss them over your tomato plants when a frost is imminent. This will keep your plants alive for at least one or two weeks longer, but it won’t be too effective if temperatures drop into the 20’s; it won’t be effective if the temperature is sustained at 32* for longer than 6 hours, either (if they make it that long, of course this depends on fabric type, mulch, plant size, etc.)

Typically, frost can occur when temperatures barely dip to 32*F, which means that plants that aren’t touched by frost can survive just fine. Tomato plants don’t enjoy anything below 40*F, so you will likely find cold damage if cooler temperatures are sustained.

The Micro Greenhouse Method to Protect Tomatoes from the Cold

If you can’t afford a traditional greenhouse, there is a budget friendly option! High tunnels clearly won’t be tall enough for most tomato varieties. However, you can build a tomato-friendly greenhouse “box.”

Start by building a cage-like frame around your tomato plant. Next, grab some greenhouse plastic (or some plastic drop cloth, if you’re on a really tight budget), and wrap the frame with the plastic. Seal the plastic against itself with outdoor weather proof tape or (the all-too-handy, budget friendly) duct tape. Done correctly, the box can pop on and off of the tomato plant as needed! Keep straw nearby, so you can tuck in the bottom of the box on colder nights.

You could also use this method below for large outdoor pots, which would apply to in-ground tomatoes as well (tomato cages could work instead of boxes, depending on the size of the plant!)

Springtime Dangers: Keeping Seedlings Alive Through the Final Frosts and Freezes

If you’re anything like me, you likely start your tomato seeds a bit early. When the seedlings are small, this isn’t a big deal; the indoor lights manage them quite well. However, when they get a little bit big a little too fast, and spring isn’t yet cooperating with us, we have to put in a bit more effort in keeping them alive.

Going Inside, and Outside

Before you can plant your tomato seedlings, you’ll have to harden them off to the sunlight. Thus, it’s a great idea to begin this process before the average last frost date arrives. On each day that’s above 55*F, bring the trays of tomato seedlings out for a few hours of sunlight. Gradually increase the amount of time that they spend outside, bringing them in when temperatures dip.

During the last few weeks, you may only find yourself bringing the plants in once or twice, allowing them to thrive in the natural sunlight. It only takes a few moments to move your tomato plants indoors, so this isn’t too much work.

Using Winter Sowing Techniques

Have you given the milk jug starter a go? Many people are turning to milk jugs for seed starting, as they act like micro greenhouses.

Start by cutting a milk jug in half, leaving one side intact to act as a hinge. Fill the bottom with seed starting mix, moisten it, sow your seeds, then close and tape the jug. Keep the lid on on colder nights; remove it during warmer days.

This is a great way to start tomato seeds if you’re a bit late; in other words, when you have 4 to 6 weeks (or less) until the average last frost date.

Covered Raised Seedling Beds

Raised beds are incredibly easy to encase in greenhouse plastic. Simply build a square frame over the bed that’s 24″ tall, wrap it in greenhouse plastic, and tuck all of your tomato plants inside! A properly insulated bed should protect tomato plants down to 28-30*F; if you have solar heating methods (such as black water sacks or barrels), you’ll see them perform even better.

If you’re particularly concerned about a dip, add several bottles of very hot water to the bed, being careful not to place them too close to plants. The heat could damage them. Bottles should be closed tightly, to radiate and retain heat. If you have mulch inside of the bed, I recommend placing the bottles under the mulch. Throw a sheet or blanket over the plastic, to help hold in the heat. As soon as temperatures begin to climb above freezing, remove the sheets and bottles.