So, you’ve planted some fall potatoes this season and they are off to a great start growing in your fall garden. But then the unexpected happens, and you get a low temperature drop right in the middle of fall when you weren’t expecting it. Naturally, you are concerned about frost, as most gardeners know how damaging they can be to plants grown above ground.
Because potatoes are grown below ground, you may assume that they can handle frost a bit better than other plants. You are correct, to an extent. When it comes to frost-tolerance, there are plenty of variables to consider, including potato variety, the soil, and moisture levels.
So, is frost damaging to garden potatoes? Will frost kill the plant? Prevent it from growing? Let’s dig a little deeper to find out!
Contents
The Short Answer
As with many topics in gardening, it depends. Most potato varieties can survive a light frost (temperatures between 28-32 degrees) with little to no damage. You may see some leaf damage, but the potato under the soil will be fine. Potato plants can survive a hard frost if you provide cold protection like a cold frame or row covers. Still, it’s best to plant your potato slips after all risk of frost has passed.
The Long Answer
Let’s look at the basics of growing seed potatoes, protect them from frost, and whether plants can recover from frost damage.
Seed Potatoes
Potatoes are grown from “seed” potatoes, which are just whole potatoes that were saved from the prior year’s crop and selected for their best qualities. The eyes are the points where the plant will sprout from. Seed potatoes are cut into pieces (each containing 2-3 eyes) or planted whole if the variety has few eyes per potato.
If you’re cutting seed potatoes for planting, allow a day or two for the cut sides to dry before planting. Otherwise, they will rot in the ground. Before planting, check that the eyes are not damaged, rotten, or have already sprouted and the stems have broken off.
Planting grocery store potatoes is not recommended since these are often treated with an anti-sprouting chemical, so they will not even grow!
We recommend that you plant in the spring after the risk of frost has passed.
Planting
Plant the seed potatoes 2-3” deep about a foot apart. Rows should be no closer than 3 feet apart, leaving enough soil in between rows to be used for mounding as they grow.
Water if the soil is extremely dry, but take care to not overwater. You risk the potatoes rotting if the soil stays too wet. Let the soil dry out completely between waterings.
Mound or hill them as they grow, covering the stems with soil and/or straw or other organic mulch. Each hilling should add about 4” of soil or mulch, up until the mound is 12” tall. Hill when the soil is relatively dry and not wet and muddy. Hilling is usually done in the spring.
Harvest full-size potatoes after the greens have died back. (Baby “new” potatoes can be harvested before the greens die back)
Frost Exposure
The good news is that your potatoes will likely survive the light frost that can sometimes appear out of nowhere in the spring. A hard frost can be a different story, but you should be able to plan ahead for that. If you see forecasted temperatures below 30 degrees, take action to protect your plants before you head to bed.
When it comes to frost, damage happens in one of two ways: cells can rupture, causing permanent damage, or the plant can go into shock. Cellular damage is most common in new plants that haven’t had a chance to harden off. While the plant may be able to recover, it’s often more susceptible to disease and pests later in the season.
Potatoes usually experience the most frost damage on the plant’s leaves since the potato itself is underground and protected from the cold air. You’ll typically see leaves that were vibrant and green become dark green or black, wilt, and eventually disintegrate.
Don’t panic if this happens. The potato has extensive reserves of energy stored in the tuber you planted, and it will send up another round of shoots. This recovery will, unfortunately, cause your potatoes to mature later than if they had been undamaged.
If there is repeated frost damage, the tuber will eventually run out of energy to recover. At this point, your plant will be dead, and you’ll need to replace it. It’s far better to take action to protect your plants from frost or plant them later in the spring.
Fall Frosts
Generally, potato crops are harvested before fall frost. If not, the green growth is probably close to having died back on its own when a hard fall frost hits. Be sure to harvest before the ground freezes. Frozen potatoes will turn to mush!
Frost Protection
Don’t worry too much if you planted your potatoes a little earlier than you should have. The tuber underground will be fine if the ground is workable and not frozen solid. And there are easy actions you can take to protect the foliage above.
Cover Your Plants
If you experience a random, unexpected frost, you can use blankets, sheets, or a tarp to protect the leaves. What we’re doing here is warming the air immediately around the foliage to prevent them from experiencing frost damage.
We recommend installing more substantive protection if you’re expecting sustained cold temperatures in the fall or spring. Cold frames or floating row covers will all do a great job of keeping the air warm around the plants while allowing sunlight to filter through.
Frost and Watering
It may seem counterintuitive, but moist soil absorbs more heat than dry soil. Watering your plants just before a frost will help keep the soil around the roots warmer. Do not water the leaves; otherwise, they’ll freeze and break off.
Mulch Your Beds
We talk about the importance of mulch a lot here. One of the key benefits of mulching is temperature control. Much keeps the soil cooler in the hot months and warmer in the cold.
Ensure your plants are insulated with a thick layer of mulch to keep them warm. You can use commercially available mulch or natural components like straw, hay, or leaves.
Can Potatoes Recover From Frost Damage?
It depends. The recovery of your potato plant depends on the severity and length of the frost damage and how often it occurs.
A potato plant that experiences light frost damage a single time will likely survive and produce a fine harvest. Any leaves and stems that die off will regrow thanks to the energy stored in the tuber below the soil’s surface.
But, if that same plant is repeatedly hit with frost damage, that energy reserve will eventually run out, and your plant will die.
When it comes to frost, it’s always better to err on the side of caution. When in doubt, cover your plants!
Final Thoughts
Potatoes are a popular food that is easy to grow and versatile in the kitchen. As always, be selective about where you source your seed potatoes and be vigilant for any signs of disease. Be attentive to the weather – especially in the spring – but don’t panic if you see minor lite frost damage.
Unless your potatoes experience repeated frost damage, they’ll likely be fine and still produce a good yield. But always err on the side of caution. Wait to plant your potatoes until after the last risk of frost and protect them from sudden temperature drops.
Happy growing!
