The cucumber plant (Cucumis sativus) is a fruiting annual plant that is grown from seed from early to mid-spring, depending on the climate. When grown in the correct conditions, cucumber plants will set fruit anywhere from 50 to 70 days from germination.
Cucumber plants are popular in home vegetable patches because these fruits are so versatile, and loved by family members of all ages. You can use them in salads, smoothies, and sandwiches, or eaten as a snack alone or as a crudités for dipping. Cucumber plants are also popular because they grow easily and require little maintenance.
They thrive in full sun and warm temperatures, and need consistently moist soil, and as long as these needs are met they will reward the grower with an abundant bounty of fruits towards the end of summer.
Cucumber plants are not hardy, but as they are annuals grown during spring and summer, they are well suited to growing in most climates where summers are consistently warm. If you live in USDA hardiness zones 4 to 12, you can grow cucumber plants outside.
Here we look at the ideal temperature range for growing cucumber plants, and how you can manage soil temperatures to help your cucumber plants thrive.
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Cucumber Plant Seedling Hardiness
If you are growing cucumber plants from seed then you’ll need to be aware of their limitations when it comes to temperatures. These are not tough seedlings when it comes to cold, so you’ll want to ensure a minimum temperature is maintained so that the seeds can germinate and seedlings can thrive.
When planting cucumber seeds you should think about where the cucumber seedlings will be kept, as this will impact what time of year you can sow them. Cucumber plants are very vulnerable to cold, and the seeds need to be grown in temperatures above 70ºF (21ºC) in order to germinate.
This means if you are sowing the cucumber seeds outside directly in the ground then you’ll need to wait until at least 2 weeks have passed since the final frost date. This ensures the soil has had the opportunity to thaw out and is warm enough to aid in the seeds germinating.
Waiting for 2 weeks also gives you added protection that the last frost has well and truly passed. You can alternatively get a head start on the season by sowing cucumber seeds indoors or in a heated greenhouse. For this, you can sow the seeds several weeks earlier, using a heated pad or a heated greenhouse to ensure temperatures do not drop below 70ºF (21ºC).
If the temperature does drop below this level, the seed will not be able to germinate. If germination has begun and the temperature dips too low, the seedling will be killed off and cannot survive.
Best Temperatures for Cucumber Plants
The ideal soil temperature for cucumbers is 75–85℉ (24–29℃), but they can tolerate temperatures a little outside of this range. For daytime temperatures, you’ll want to make sure that your cucumber plants are experiencing a minimum of 65℉ (18℃).
The type of location you are growing your cucumbers in is going to affect the temperature of the soil and the overall growth of the plants and their fruits.
Cucumber Plants in Greenhouses
Cucumber plants do very well when grown in greenhouses because they prefer consistently high temperatures, which greenhouses are able to offer. If you are trying to grow cucumbers in a climate that is not consistently warm, then using a greenhouse will give you a much better chance of success with these plants.
Greenhouses are made of glass, which traps the sun’s heat, and enables them to be considerably warmer than the outdoor temperature. Even during the evening when the sun is no longer shining on the greenhouse, it maintains a higher temperature than outside.
This is great for cucumber plants, which will have stunted growth when subjected to low temperatures. If the heat becomes excessive in a greenhouse, move the cucumber plants outside, or leave the doors and windows open for ventilation.
Cucumber Plants Outside
Cucumber plants are annuals that can be grown in USDA hardiness zones 4 through to 12, so as long as the final frost has passed then you should be able to grow cucumber plants outside in your garden with success. As these plants thrive in soil temperatures in the range of 75–85℉ (24–29℃), you need to ensure they are in a warm spot.
Avoid planting them in the shade where the soil will be cooler. Cucumbers also require plenty of sunlight on their leaves to thrive, so positioning them in a sunny spot will be best.
To help the soil maintain a warm temperature, you can add mulch over the soil which will act as an insulator. This also helps to prevent moisture evaporation, ensuring the roots of the plant get the hydration they need.
Cucumber Plant Night Temperature Tolerance
Temperatures in most regions will drop during nighttime, and this can be a problem for cucumber plants if the temperature dips too low. Cucumber plants perform best when the soil temperature does not drop below 65℉ (18℃), however, they can tolerate nighttime temperatures down to 55℉ (13℃).
If the temperature gets any colder than this, then the cucumber plant is at a high risk of not surviving. When the temperatures enter the 40’s, the cucumber plant will not immediately die but instead will sustain obvious damage to the leaves, stems, flowers, and fruits. If the temperature remains below 50℉ (10℃) for several nights, then the growth of the cucumber plant will stop, and it may not be able to recover, even when the temperatures rise again.
Cold damage can present itself as wilting foliage, or brown marks on the leaves and fruits. Once a cucumber plant has sustained cold damage, even if it survives, it will be more susceptible to disease in the future. For these reasons, it is important to keep cucumber plants at suitable temperatures.