what does frost do to potato plants

When frost threatens, it is natural to worry about the plants in your garden – but should you worry about potato plants? Potatoes are a cool weather crop, but that doesn’t mean they are invincible. So, can potato plants survive frost? Potato plants can survive a light frost (temperatures of 28 to 32 degrees Fahrenheit), usually with little or no damage. Potato plants can also survive a hard frost (temperatures below 28 degrees Fahrenheit), especially with cold protection (such as cloches or row covers). In some cases, the cold from a hard frost may damage potato plant leaves and stems, killing the plant above ground. However, new shoots can emerge from the seed potato underground and continue growing. Of course, there are ways to protect your potato plants from cold, whether they are young or established. This will give them a better chance of survival, no matter what the temperature. In this article, we’ll talk about the signs of frost damage in potato plants. We'll also look at some ways you can protect potato plants from frost. Let’s begin. Can Potato Plants Survive Frost? A potato plant can survive light frost in spring. According to the Michigan State University Extension, a light frost means temperatures of 28 to 32 degrees Fahrenheit (-2 to 0 degrees Celsius). Potato plants can survive light frost, but hard frost may damage the leaves and shoots in some cases. In some cases, potato plants can survive a hard frost. A hard frost means temperatures less than 28 degrees Fahrenheit (-2 degrees Celsius). However, temperatures below 28 degrees Fahrenheit could kill the part of the potato plant above the soil. At that point, the plant would need to start from scratch by sending up new growth, costing time and energy. It is important to remember that freezing refers to temperature, and frost refers to visible frost on the ground or plants. It is possible to see both of the following situations: freezing temperatures without visible frost (the temperature is below 32 degrees Fahrenheit, but there is no white frost on grass or leaves of plants).visible frost without freezing temperatures (the temperature is above 32 degrees Fahrenheit, but there is white frost on grass or leaves of plants). It is possible to have frost without freezing temperatures, and vice versa. The appearance of frost depends on both the air temperature and the dew point – you can learn more in this article from the Michigan State University Extension. Potatoes are a cool season crop, but that doesn’t mean they like it cold all the time. According to the Old Farmer’s Almanac, some gardeners plant potatoes 6 to 8 weeks before the last frost date. However, some gardeners like to wait until 2 to 4 weeks before the last spring frost date to plant potatoes. This reduces the chance of a late spring frost killing the plants. The Old Farmer’s Almanac suggests that the soil temperature should be at least 50 degrees Fahrenheit (10 degrees Celsius) before planting potatoes. You can use this tool from the Old Farmer’s Almanac to find the last spring frost date in your area. Later in the season, potato plants will grow better with warmer temperatures. According to the University of Illinois Extension, potato tubers form best at soil temperatures of 60 to 70 degrees Fahrenheit (16 to 21 degrees Celsius). What Does Frost Damage Look Like On Potato Plants? According to the Iowa State University Extension, minor cold damage on potato plants will result in black edges (margins) on the leaves. In more severe cases, all of the plant that is above ground (shoots and leaves) will succumb to extreme cold. A hard frost can cause black edges on the leaves of a potato plant.Image courtesy of:Victor M. Vicente Selvasvia Wikimedia Commons: https://commons.wikimedia.org/wiki/File:Patatera_gla%C3%A720170422.jpg The extent of the damage will depend on: Cold Severity (how far below freezing is the air temperature?)Length of Exposure (how long was the plant exposed to the cold?)Frost Protection (how much protection did the plant have against the cold?) So what does frost do to potato plants? Although potatoes can tolerate some frost, they may suffer from signs of frost damage, including: minor damage to leaves (black leaf margins or edges)major damage to stems (wilting or death of plant above ground) However, you shouldn't need to replant in this case. According to the Iowa State University Extension, the potato plant will send up new growth after frost damage early in the season. Do Potato Plants Recover From Frost Damage? In some cases, a potato plant can recover from frost damage. In cases of minor frost damage, the plant’s shoots will continue growing and producing new growth (even when some leaves are damaged). If a potato plant dies back to the ground due to early spring frost, it may send up new shoots. In a case of major frost damage, the leaves and shoots above ground may not recover. However, according to the Iowa State University Extension, the potato plant will send up new shoots in 10 to 14 days. As long as the plant has enough stored energy, it should be able to regrow and eventually produce tubers. However, it might take longer to get a harvest later in the season, and the harvest might be reduced. Can Potatoes Stay In The Ground After Frost? (Harvesting Potatoes After Frost) Potatoes can stay in the ground after frost. If the potato plant above ground survives the frost, then it can continue to grow the tubers. Don't leave potatoes exposed out in the sun, or they'll turn green and produce toxic solanine. If the potato plant does not survive frost, the tubers will still be safe underground – they just won’t grow any more. You can harvest the tubers at any point after the plant dies back. Just be sure not to wait too long to harvest the tubers. If the ground freezes, it will be almost impossible to dig your potatoes! After digging up your potatoes, be sure to cover them from sunlight. Otherwise, they will turn green and may produce solanine (a toxic substance). A potato left out in the sun will turn green and produce toxic solanine.Image courtesy of user:Anicius Olybrius via: Wikimedia Commons: https://commons.wikimedia.org/wiki/File:Evil_green_potato.jpg Bring your potato tubers indoors to brush the dirt off and cure them before storage. It might be in your best interest to leave the potatoes in a dry, warm area (out of sunlight) for a short time. According to the University of Michigan Extension, it will take about 2 weeks for potato skins to toughen up (this prepares them for storage). Don't wash them, though - that could lead to mold growth. Only wash your potatoes right before you use them for cooking. You should store potatoes in a cool, dry, dark place to prevent them from sprouting. If your potatoes do sprout, you can learn how to plant sprouted potatoes in my article here. Potatoes are technically perennial, but are often treated as annuals in gardens - you can learn more in my article here. How To Protect Potato Plants From Frost It is true that potato plants can survive frost. However, Mother Nature will sometimes surprise you with a rapid dip in temperatures (possibly much colder than the weather forecast called for!) It is also possible that you live in a microclimate (in your region or even in your yard). This can make the temperature much colder than the surrounding areas. There are a few ways to protect potato plants from frost. In those cases, it makes sense to protect your potato plants from cold. Not only will this prevent damage to the leaves and shoots above ground, but it will give the tubers more time to develop. You should cover your potato plants whenever a frost threatens (freezing temperatures have the potential to cause damage, and it can get colder than the weather forecast suggests). There are 4 methods that you can use to protect potato plants from frost: Cloche – this is good for younger plants that have just emerged from the soil.Row Cover – this is good for larger, more established plants, or for an entire row of plants.Greenhouse – this requires the most work to setup, but it can keep your plants quite a bit warmer than the outside air.Hilling - this is standard procedure for growing potato plants, since it helps to prevent green potatoes (which occurs due to sunlight exposure). However, hilling will also protect young potato plants from late spring frost by insulating them against changes in air temperature. Cloche A cloche is a clear cover made of plastic or glass. In a garden, it is used to protect plants from cold, wind, and pests. A cloche acts as a sort of “mini greenhouse” that traps heat from sunlight. This warms the air and soil underneath the cloche. A cloche often has a vent on top to let in fresh air and prevent it from overheating. Most cloches are meant for a single young plant. You can make a cloche out of the top of a plastic bottle by cutting out the bottom. However, you can also find “row cloches” that cover multiple plants. Another option is to use wire cloches. By itself, a wire cloche will not protect a plant from cold. However, you can wrap a frost blanket or row cover over a wire cloche to provide frost protection. You can learn more about cloches and how to use them in my article here. Row Cover (Frost Cover) A row cover is a sheet of lightweight fabric that protects plants from cold, wind, and pests. A row cover is often made of polyethylene, polyester, or polypropylene. Row covers vary in thickness, which determines the amount of light that gets through. Thicker row covers are heavier, but allow less light through and offer more cold protection. Depending on the thickness, a row cover can provide 2 to 10 degrees Fahrenheit (1 to 6 degrees Celsius) of cold protection. Heavyweight row covers are better for protecting plants from hard frost or intense sunlight. Another advantage of row covers is that you can water through them (since they are water permeable.) Often, a series of half-hoops are used to support a row cover. That way, the cover won't come in contact with the plants themselves (if they do, it can allow frost damage to occur). Half-hoops provide support for row covers to raise them above plants. You can learn more about row covers and how to use them in my article here. Greenhouse A greenhouse is a structure with glass or plastic sides and roofing. It traps energy from sunlight and warms the air and soil inside the greenhouse. Some greenhouses have vents to let in air if the temperature inside gets too hot. Otherwise, you will need to open the door slightly to allow air circulation. A greenhouse keeps plants warm and can house potato plants for the whole season. A greenhouse is a good option if you want to keep potato plants warmer throughout the growing season. This will help you to avoid damage from both spring and fall frost. In an area with a short growing season, a greenhouse could help you to get a much better harvest. Hilling Hilling potatoes means to pile up soil (or mulch) around the base of a potato plant as it grows. This serves multiple purposes: it keeps tubers underground and out of sunlight (this prevents tubers from turning green and producing toxic solanine).it keeps the plant warmer by insulating against rapid temperature changes. Hilling is a good way to keep potato plants a bit warmer, especially when combined with cloches, row covers, or a greenhouse. Hilling potatoes prevents the tubers from turning green and can protect plants from frost. Hilling will also allow more of the plant to survive if a heavy frost does manage to kill the part of the plant above ground. Conclusion Now you know about how frost affects potato plants. You also know how to protect them from cold in the early stages and later in the season. You might find it helpful to read my article on the best temperature for growing potatoes and my article on growing potatoes in winter. Hilling potatoes also helps to protect them from cold- you can learn more about why you should do it in this article. You might also want to learn more about cold protection equipment for plants (and where to find it) in my article here. You can also learn about which vegetables will survive frost in my article here. I hope you found this article helpful. If so, please share it with someone who can use the information. If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here. Enjoy! ~Jonathon