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So, what does the cold weather mean for our potato crops?
Potatoes are frost tolerant up to a point but will not continue to grow over the winter. Consistently cold temperatures will kill the greens of the plant and any tubers left in the ground will go dormant before sending up new sprouts in the spring.
Keep reading to learn all about how to protect your potatoes from frost and how to extend the potato growing season.
Are potatoes frost tolerant?
One of the nice qualities of potatoes is that they are frost tolerant up to a certain point. They can handle some light frosts without causing major detriment to the tubers. But, once you get a hard freeze in the fall or winter, the greens of the plant are likely to die back completely.
Before we keep going, I should clarify the difference between a frost and a freeze. A frost can happen even if temperatures don’t get all the way down to 32 degrees and will be visible on the leaves of the plant.
As the late summer season transitions to fall, you’re likely to have some frosty nights that quickly warm up by mid-morning. Your potatoes can withstand this kind of frost.
On the other hand, a hard freeze is when temperatures get below 28 degrees and stay that low for an extended period. These are the temperatures that will kill your potatoes and most of the other things that are still in your garden.
How late can you harvest potatoes?
To determine how long you can keep your potatoes in the ground, it’s important to know your first regional frost date. Depending on what hardiness zone you live in, your first frost date will be earlier or later in the fall.
Not sure when your regional frost date is? You can put your zip code into this website and it will tell you!
You want to have your potatoes harvested before the ground freezes completely. Otherwise, you’ll have a very difficult time digging them out.
I like to lean on the safe side and harvest all of my potatoes before Thanksgiving. If you live somewhere warmer, you may be able to push this date by a couple of weeks.
If you do happen to leave them in the ground overwinter, there is a chance that the tubers may survive and send up new shoots in the spring. But this can be hit or miss and the tubers in the ground will rot before producing new potatoes.
How to protect potatoes from frost
If you see a frost coming in the weather forecast, there are some season extension techniques that you can employ to help protect your potatoes.
Row cover
This is the most common method for protecting plants from cold temperatures. Frost cloth or reemay is like a giant blanket that goes over plants to keep them warm.
It’s important that the fabric doesn’t touch the plants as this can cause damage to them. So make sure you put metal hoops over your rows that you can drape the frost cloth over.
Once you’ve put the cloth on, you’ll need to find some weight to hold it down so that the wind doesn’t blow it away. I usually just use some bricks that I have lying around but many people use sandbags too. Really anything heavy will work.
Frost cloth comes in many different sizes and thicknesses which will affect how warm it keeps your plants. In general, a frost cloth will keep your plants 3 degrees warmer than it is outside.
If it’s supposed to get really cold, you can even add a second layer of frost cloth for some added insulation.
The only downside to using frost cloth is that it makes it more difficult for sunlight to reach your plants. Therefore, you shouldn’t leave it on for a long time. Frost cloth is a short-term solution.
If the temps are only cold at night, then you can cover your potatoes in the evening and uncover them in the morning once it’s warmer. I wouldn’t leave frost cloth on plants for longer than a day.
If the temps get cold and stay that way, it’s best to harvest what you can while you still have the chance.
Other covers
If you don’t have long rows of potato plants, then row cover might be a bit impractical for your garden. For gardens that just have a handful of potato plants, you can cover them with some cardboard boxes or paper bags.
Just like with frost cloth, make sure to uncover your plants during the day to make sure that they still have access to sunlight.
Hilling
Hilling is the process of piling up soil along the sides of your potato plants. Usually, this is done throughout the growing season to help promote new growth on the plant and increase tuber yield.
But, it can also be used as a form of frost protection. By hilling your plants, you’re giving your underground tubers an extra layer of insulation to help keep them warm.
Grow frost-tolerant varieties
This is more of a proactive season extension tip than a reactive one. If you’re hoping to get more out of your potato harvest this year, then choose to plant some varieties that are more frost tolerant.
Frost-tolerant potato varieties include Russet, Elba, or Lehigh.
Can potatoes be grown in the winter?
If you live in a warmer climate or have an indoor growing space like a greenhouse, then there’s potential to continue growing potatoes through the winter.
Otherwise, it’s very unlikely that any potatoes will grow over the winter. Especially if temps are consistently below 32 degrees. Once the foliage dies back, any tubers still underground will go into a dormant state and won’t send up new shoots until the soil temps start to warm back up.
If you’re not sure you’ll be able to harvest all of your potatoes before the ground freezes, you can try adding a layer of straw insulation to your beds to help keep them a little warmer and give you some more time to harvest.
Conclusion
So now you know everything you need to know about protecting your potatoes from frost. My number one suggestion is to make sure you cover them with frost cloth or even a cardboard box if you know of any cold temps coming your way.
Try to harvest any tubers still in the ground before it freezes completely. Once the ground is frozen it’s very difficult to dig in, if not impossible.
Any tubers that stay in the ground over winter have the potential to send up new sprouts in the spring. But, there’s no guarantee they’ll make it through the winter.
Your best bet is to harvest what you can in the fall and prepare to plant a fresh round of seed potatoes in the spring!