While peppers love heat, too much heat and humidity can prevent plants from producing well. You may see flowers simply drop from plants without ever making fruit. Wait it out until the heat wave subsides, and plants should bounce back. If you typically have periods above 90°F, plant heat-tolerant varieties.
Dry soil, temperatures above 90°F, or night temperatures below 60°F or above 70°F, can weaken plant growth. Transplant in late afternoon or on a cloudy, calm day. Pepper flavor is best when the season has been warm and sunny. Fruit that matures under cool or cloudy conditions will not be as tasty.
Temperatures below 60°F at night will also result in blossom drop. At temperatures below 40°F, peppers may show some chilling injury.
Ideal growing temperatures are between 70 and 90 degrees during the day and 60 to 70 degrees at night. Temperatures above 90 degrees during the day can also cause blossoms to drop. Hot peppers do well in temperatures even warmer than those sweet peppers can tolerate and will set fruit at temperatures above 90 degrees.
Peppers are known to thrive in a temperature band of 60 to 85 degrees. In the summer they spend a lot of time in my garden in a band of 85 to 100 degrees.
They grow well in raised beds, containers, and in-ground gardens. Plant them 18 to 24 inches apart in a sunny, well-drained spot. Pepper plants need at least 6-8 hours of sunlight per day. Mix compost or other organic matter into the soil when planting.
So, how hot IS too hot for plants? The general answer is around 90 degrees F, with some exceptions to the rule. This means that when temps rise above 90 and remain there for a lengthy spell: Leaves wilt.
Sunscald on Peppers
It can affect both leaves (leaf scorch) and fruits. Tender plants that are not adjusted to direct sunlight are the most vulnerable. Pepper plants require a gradual transition from their indoor environment to their home outdoors.
Summer squash, such as zucchini and yellow squash, thrive in warm temperatures between 70-95°F (21-35°C). They can tolerate some heat but may become stressed if temperatures exceed 100°F (38°C).
Plant Care
Sweet peppers can cope with a minimum night temperature of 12°C (54°F), but will grow better if kept above 15°C (59°F). But they don't like to be too hot – temperatures over 30°C (86°F) can reduce fruiting, so keep the greenhouse well ventilated and put up shading in summer.
In the case of peppers, the ideal daytime temperature is 21-26°C (70-80°F). The ideal nighttime temperature is 18-21°C (65-70°F). Of course, these ranges may vary, depending on the pepper varieties you grow. Pepper plants may still grow outside of the ideal temperature range.
Covering plant material at temperatures between 39-30 with freeze cloth or covering can be effective. Prolonged exposure at temperatures of 28 degrees and below will notice protection results diminish with each degree dropped.
Inadequate Watering
Watering your pepper plants can be a major focus area for them not growing adequately. Underwatering pepper plants - especially young seedlings or newly transplanted plants - definitely stunts their growth and dries them out completely.
Hot peppers get hotter the longer they are left on the plant, but you can harvest and use them when they are green. Most peppers change color as they mature, which is an indicator that they are fully ripe.
For pepper plants, a balanced fertilizer with equal proportions of Nitrogen (N), Phosphorus (P), and Potassium (K) is recommended. However, pepper plants respond positively to higher nitrogen concentrations during the flowering stage.
Plants can experience heat stress when temperatures are above 90 degrees for a prolonged period, or if temperatures are above 104 degrees even for a short time. The heat stress is compounded when it's windy and the soil starts to dry out.
Veggies & Fruits
Vegetables typically require daily watering during summer weather, but may need a second watering when temperatures are extremely high. Lettuces and other leafy crops can be kept from bolting (going to seed) by misting or watering their leaves in the afternoon.
People have asked, can peppers survive 40˚ F temperatures? Most peppers are not happy when temperatures drop below 50-60˚ F.
If leaves are turning brown on your pepper plants, it may also be because you forgot to water them. When leaves get brown and crumble, especially when accompanied by the dropping of leaves and the drooping of the plant, it's likely that the plant is underwatered.
Peppers require consistently moist soil for optimal growth. The soil should be kept damp but not waterlogged to prevent root rot and other issues. A general rule of thumb is to water deeply once or twice a week, though this can vary based on weather conditions and soil type.
During extremely hot weather (daytime temperatures above 90F and nighttime temperatures above 70F), try to water daily or every other day. In a 10x10-foot garden, this would mean giving your plants 8 to 9 gallons of water each day.
Cucumbers are like the Goldilocks of the garden; they prefer it not too hot, not too cold, but just right. Daytime temperatures should hover between 60-95°F (15-35°C), with the sweet spot around 70-82°F (21-28°C) for those juicy, crunchy fruits.