Most plants slow down their growth and production in temperatures above 90 degrees. Tomatoes, for example, which are a warm season crop to begin with, basically stop growing or producing leaves, stems and tomatoes around 90-95 degrees.
For many plants, temperatures below 50°F can cause problems. Adjust thermostats to cater to your comfort, but remember your plants need some consideration. Avoid placing plants near cold drafts or heat sources. Keep plants several inches away from exterior windows.
I did some research and found out that houseplants need to be taken indoors before overnight temperatures dip below 45 degrees. Most tropical plants suffer harm from temperatures below 40 degrees. Well, we have temperatures forecast to dip into the 40s again on Thursday and lower 40s on Friday.
It's important to keep an eye on the weather – specifically the night ranges – and ensure that your green friends are never outdoors in degrees lower than 45 degrees. If you care for tropical plants, anything lower than 40 degrees will cause severe harm.
Each plant has a different threshold when it comes to dealing with the cold. Some plants can survive outside even when temperatures hit freezing. Others need to be brought indoors when temperatures reach the mid-40s. Be sure you know this before you plant.
When Should You Cover Plants? Cover your plants at night and remove them during the day when the temperatures rise above 32 degrees F, so that the soil can warm up again. Some outdoor plants won't survive the harsh conditions of winter, bring them inside and use these tips for caring for them through winter.
If you're wondering at what temperature threshold you should be bringing your plants, there's a short answer: when nighttime temperatures reach 45 degrees (F), it's time to bring your plants indoors.
It's important to pay attention to the temperature dropping when the sun goes down. Once temperatures are consistently between 60 and 45 degrees Fahrenheit, it's a good idea to start bringing your plants inside at night. However, you can keep them out during the daylight hours if the temperature stays above 45 degrees.
Most plants prefer a temperature of no less than 60° F, though many can tolerate as low as 40° F. Along with this, while the improper temperature can certainly be an issue, fluctuations in temperature are the true killer. Learn the ideal temperatures for your green friends so they can be healthier and happier.
WHEN TO BRING PLANTS INSIDE. As a general rule, tender plants should be brought in when nighttime temperatures are below 50 to 55 degrees F, even if they are hardy for your zone. A plant's roots are more exposed when planted in a container versus in the ground.
Avoid watering when temperatures are below 40°F or when sustained freezing temperatures are expected within 24 hours as this water will freeze and not be available to the plants.
Thoroughly Water plants if it's not going to rain before the freezing temperatures arrive. It may sound illogical. However, a moist ground stays warmer than dry soil. Watering the night before the freeze comes will insulate the root structure of the grass and plants and decreases the potential for cold injury.
Light freeze - 29° to 32° Fahrenheit will kill tender plants. Moderate freeze - 25° to 28° Fahrenheit is widely destructive to most vegetation. Severe or hard freeze - 25° Fahrenheit and colder causes heavy damage to most plants.
Know The Limits
In order to understand what steps to take when freeze warnings threaten, you need to know the point at which treasured greenery fades to frost-burned brown. The general rule of thumb is that most plants freeze when temperatures remain at 28°F for five hours.
“Houseplants don't actually go dormant like a lot of people think,” he says. They do, however, react to the climatic changes in your home. Your home is dryer in the winter. Hot dry air from furnaces, space heaters, and fireplaces (which also means less humidity) are factors for the decrease in houseplant growth.
Most tropical plants such as ferns, palms, spider plants, pothos, and philodendrons love cold nights between 60 to 65 degrees. However, they cannot tolerate chilly nights going below 50 degrees. Anything lower than that results in stunted growth and, ultimately, demise.
Temperatures below 32 degrees can freeze the leaf tissue of cold-wimpy plants and turn them to mush after just a few hours. Some of the most tender annuals and veggies might not die but suffer cold-induced setbacks even when overnight lows dip below 40.
Hardy cool-season crops (cabbage, broccoli, onions, radish, spinach, turnips, peas, and radish) grow in 40 degree daytime temperatures and can handle some frosty nights without protection.
A covered porch usually provides protection from light frost, but the garage or sun room is better for freezing temperatures. A couple days in darkness won't hurt the plant. Or move them out during the day and back in at night, if cold temperatures persist.
As a whole, all tender plants should be brought indoors or protected with garden fabric to prevent frost when it is 36°F outside. For cold-hardy plants, this is entirely optional. But it's better to err on the side of caution when the temperature falls below 40°F.
Some cool-season annuals can tolerate soil temperatures as low as 45 degrees Fahrenheit; however, most cool-season annuals will grow best in soil temperatures at 65 degrees Fahrenheit or warmer.
Most houseplants are tropical plants that can safely grow in a heated home during the winter. They will never survive outdoors in winter unless you live where the temperature stays at least above 50 degrees.
As gardeners, our frost dates are based on 32 degrees Fahrenheit (0 degrees Celsius) to avoid the risk of any plant death. However, know that even if air temperatures are as high as 38°F, frosts may occur on the ground and on plants. It's better to protect plants just in case!
Tomato plants, in general, can survive temperatures down to 32°F for short periods of time. But sustained temperatures below 50°F can cause slowed growth, severe damage to foliage and fruit, and ultimately, death.