how cold can cucumbers tolerate

When spring finally arrives and the ground thaws out, it can be so tempting to plant seeds and start your garden right away. However, you don’t want to rush things, since certain plants are sensitive to cold, including cucumbers. So, what is the lowest temperature cucumber plants can tolerate? A temperature of 32 degrees Fahrenheit (0 degrees Celsius) or below will result in frost, which will kill cucumber plants. Any temperature below 50 degrees Fahrenheit (10 degrees Celsius) will result in slower growth of cucumber plants, and will eventually damage them. Cucumber seeds will not germinate (sprout) in soil colder than 60 degrees Fahrenheit (15.6 degrees Celsius). Of course, cucumber plants really thrive at temperatures of 75 to 85 degrees Fahrenheit (23.9 to 29.4 degrees Celsius). While you are waiting for those warmer days to arrive, there are some steps you can take to protect your cucumber plants from the cold. What Is The Lowest Temperature Cucumber Plants Can Tolerate? Cucumber plants are warm weather plants, native to India. Like other vine crops (such as squash and melons), cucumbers are very sensitive to cold. Cucumber plants are a warm weather crop, and are very sensitive to cold. A frost will kill them. According to Texas A&M University, even a light frost will kill cucumber plants. Frost occurs when air temperatures are around 32 degrees Fahrenheit (0 degrees Celsius). Cucumber seeds will not germinate in soil colder than 60 degrees Fahrenheit (15.6 degrees Celsius). Just to be safe, you should start cucumber seeds indoors to keep them warm enough for germination. Cornell University suggests transplanting cucumber plants outside to the garden after the soil warms up to 65 degrees Fahrenheit (18.3 degrees Celsius). Generally, this will be at least two to three weeks after the last frost date in your area. You can use this resource from the Old Farmer’s Almanac to find frost dates in your location. According to the Penn State University Extension, air temperatures below 50 degrees Fahrenheit (10 degrees Celsius) will slow the growth of cucumber plants. To avoid this, you may want to use cloches to protect young plants, or row covers to protect mature plants (more on this later). According to the University of Georgia Extension, cucumbers thrive and grow their best at temperatures of 75 to 85 degrees Fahrenheit (23.9 to 29.4 degrees Celsius). Since warm temperatures are so important for growing cucumber plants, we will spend some time going over ways to keep them warm and protect them from the cold. Choose the Right Cucumber Varieties One way to help protect your cucumber plants from cold is to choose the right varieties in the first place. Based on where you live, the USDA plant hardiness zone map will tell you what zone you are in. In general, the lower the zone number, the harder it will be to grow warm-weather crops such as cucumbers. If you live in a colder region, consider cold tolerant or fast-maturing cucumber varieties to help even the odds in your favor. Cold Tolerant Cucumber Varieties I did a little research to find some cold-tolerant cucumber varieties that can grow well in cooler climates. Here are a few examples: Socrates – the Socrates cucumber matures in 52 days and is tolerant of cooler temperatures. The fruit is 7 to 8 inches long, with dark green skin and no seeds. This variety is Parthenocarpic, meaning it sets fruit with no pollination. It is also resistant to powdery mildew.Corinto – the Corinto cucumber is an F1 Hybrid variety, maturing in 48 days and more cold tolerant than your average cucumber plant. The fruit comes early, is 7 to 8 inches long, and has dark green skin. It is resistant to multiple cucumber diseases, including powdery mildew.Wisconsin – the Wisconsin cucumber is a pickling cucumber, maturing in 65 days and bred to produce in the colder northern regions. It is resistant to multiple cucumber diseases, including cucumber mosaic virus. You can find more information on these and other cucumber varieties on the Cornell University website. Fast Maturing Cucumber Plants Even if you are worried about a short growing season in your region, you can still get a good cucumber harvest, provided that you grow them fast enough. There are several fast-maturing cucumber varieties to choose from – here are just a few. Bushy – the Bushy cucumber is a Russian bush variety, maturing in 46 to 49 days. The vines are 3 to 5 feet long, and the fruit is good for making pickles.Russian – the Russian cucumber is an heirloom from Russia, maturing in 50 days. The medium-green fruit is 6 to 8 inches long, and good for pickling.Amour – the Amour cucumber is a pickling variety, maturing in 47 days. The dark green fruit is 4 to 5 inches long. This variety is Parthenocarpic, meaning it can produce fruit without pollination. It is resistant to multiple cucumber diseases, including powdery mildew. You can find more information on these and other cucumber varieties on the Cornell University website. Planting Schedule To avoid cold temperatures and frost, it is important to plan ahead. That way, you can plant cucumber seeds and transplant outdoors at the right times. The Old Farmer’s Almanac suggests starting cucumber seeds indoors about 3 weeks before you plan to transplant them outside. It also suggests transplanting cucumbers outdoors 2 or more weeks after the last spring frost date. Start your cucumber seeds no earlier than 1 week before the last spring frost date in your area. This means that you should plant cucumber seeds indoors no earlier than 1 week before the last spring frost date. Start Seeds Indoors For most cucumber seeds, the soil temperature needs to be at least 60 degrees Fahrenheit (15.6 degrees Celsius) to achieve germination. Ideally, the soil should be warmer than that (65 to 95 degrees Fahrenheit). Unfortunately, the soil may not get that warm until later in the season. There are two ways around this: you can either buy established cucumber plants, or start cucumber seeds indoors. If you decide to start cucumber seeds indoors, you will need to keep the soil warm enough for proper germination. Remember that the seeds of most cucumber varieties will germinate best in soil temperatures of 75 to 85 degrees Fahrenheit (23.9 to 29.4 degrees Celsius). One way to heat up the soil is to use a seedling heat mat. A heat mat uses electricity to produce heat, and the heat warms up a container of soil placed on top of the mat. You can also cover a container with plastic wrap and leave it on a sunny windowsill to warm the soil. Remember that you can use either artificial light or sunlight to grow your cucumber seedlings. If you place seedlings close to an old window, don’t let them get caught in a cold draft. Otherwise, your efforts to grow cucumbers will fail before you ever really get started! Watch the Weather Forecasts Even if you pick cold-tolerant cucumber varieties and time your planting carefully, Mother Nature may still have a surprise in store for you. Although frost dates are usually reliable, you will sometimes see a growing season with strange weather patterns. You can learn more about frost dates and what they really mean here. In any case, you should keep an eye on the weather forecast, especially as the time approaches to transplant your cucumber seedlings outdoors. If the forecast calls for some unseasonably cold weather or a very cold night, keep the cucumber seedlings indoors for a little longer to keep them safe. Wait until soil and air temperatures warm up before transplanting cucumber seedlings outdoors. If you choose a cold-tolerant cucumber variety, you might be able to get away with transplanting them outdoors sooner. However, it is always advisable to watch the weather and plan accordingly. Select the Best Location If you plant some of the cold-tolerant cucumber varieties that we discussed earlier, you might be able to put them in cooler areas of your garden that get a little bit less sunlight. However, cucumbers grow best in full sunlight, so they will do their best in a sunny spot in the garden. In addition, more sun exposure will make the soil warmer during the day, and that heat will last longer at night. Protection from wind can also keep your cucumber plants a little bit warmer at the start of the season. There are a few different ways to protect cucumber plants from cold and wind, including cold frames, black plastic, cloches, and greenhouses. How to Protect Cucumber Plants from Cold and Frost There are lots of ways to protect your cucumber plants from cold and frost - let's start off with cold frames and go from there. Use a Cold Frame for Seedlings There may be times when you want to transplant your cucumber seedlings outside a little earlier in the season than recommended. There are other times when your spouse yells at you for having too many plants in the house. In any case, a cold frame will help to keep your plants warm after you move them outdoors. A cold frame is a short wooden structure with a glass top, sort of like a miniature greenhouse. Many cold frames automatically open if the temperature inside gets too high. They will close again when it gets cold inside, thus “self-regulating” their internal temperature to some extent. Once your cucumber seedlings are mature enough, you can move them directly into a cold frame. To determine if the cold frame is getting warm enough for cucumber transplants, put a thermometer in the cold frame and monitor it every day. As always, watch the weather forecast and be prepared for frost or unseasonably cold weather! Use Black Plastic to Warm Up the Soil If the days are sunny but cool, you might be able to use the sunlight to your advantage to warm up the soil. Take a piece of black plastic and put it over the soil where you want to plant your cucumbers. The black plastic will absorb most of the energy from the sun, and will warm up the air and soil beneath it. The greenhouse effect will then prevent the heat from leaving the soil and air under the plastic. According to the University of Massachusetts at Amherst, you can leave the black plastic in place during the growing season. Just use a trowel to cut holes in the plastic, and plant your cucumber transplants into the holes. Just make sure there is enough moisture in the soil before putting the black plastic in place. You will also need to apply fertilizer before laying down the plastic if you plan to leave it during the growing season. Use Cloches for Young Plants A cloche is an easy and cost-effective way to keep young cucumber plants warm during cold weather. A cloche is simply a cover meant to protect plants from wind and cold temperatures. Originally, a cloche was a bell-shaped glass cover to put over plants. Now, a cloche is usually made of plastic. A wire cloche can be used to protect plants from rabbits or other creatures. However, a wire cloche won’t keep the plants warm, unless you also put plastic or row cover material over it. The top of a cloche has a hole, which lets plants breathe and allows excess heat to escape. Conveniently, a cloche can also deter some pests from damaging your cucumber plants. If you want to make your own cloche, simply collect empty clear plastic gallon containers of milk or water. Then, cut out the bottom, and put the container over your plants. You can cut the bottom out of empty clear plastic bottles to make your own cloches. Make sure to remove the cap on top of the gallon jug to allow the plants to breathe on hot days. After all, you the last thing you want is to kill them with heat after protecting them from the cold! The one drawback of using a cloche is that your cucumber plant will outgrow it. However, a cloche is a great method for keeping young plants warm if they are transplanted outside early in the season, or if cold weather comes late. Use a Greenhouse for Taller Plants You may need to protect your cucumber plants from cold later in the growing season. In that case, transplanting them directly into a greenhouse is a good choice. A greenhouse keeps cucumbers and other plants warm during the growing season. You can build a custom greenhouse on your own or hire someone to build one for you. You could even buy a pre-fabricated greenhouse and put it together yourself. Before transplanting cucumbers, put a thermometer inside the greenhouse and check the temperature. When temperatures during the day are above 75 degrees Fahrenheit (23.9 degrees Celsius), then you can think about moving your transplants to the greenhouse. Right after you move cucumber plants to the greenhouse, keep the door closed at night to trap heat inside. Otherwise, you might damage or kill your cucumber plants on a single cold night! Keep in mind that high temperatures can also kill cucumber plants, or at least slow down their growth. A greenhouse can generate those high temperatures inside, so be sure to open the greenhouse door in the morning before a hot, sunny day (again, check the weather before you leave the house!) Use Row Covers For Taller Plants What if your cucumber plants grow too tall for cloches and need cold protection towards the end of the season? In that case, you can use row covers to keep them warm. One method is to bend flexible plastic rods into half-hoops, with the ends stuck into the ground. When you have enough of these rods lined up over your row of cucumber plants, put a long piece of garden fabric on top of the hoops. You may need to use rocks to hold the fabric in place. You might also need to remove the fabric on hot days, so be mindful of what the weather is doing. Row covers will also protect your cucumber plants from pests – just an added bonus of this method of cold protection! Conclusion Now you know how much cold your cucumber plants can tolerate before they slow down growth or die from cold. You also know how to protect your cucumber plants from cold weather, extend the growing season, and improve your harvest. You might also want to read my article on why cucumber plants wilt after transplant. I hope you found this article helpful – if so, please share it with someone who will find the information useful. It’s time to get back to the garden and protect your cucumber plants from the cold! If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here. Enjoy! ~Jonathon