Will 39 degrees hurt plants?

Author: Kathlyn Fritsch  |  Last update: Sunday, July 6, 2025

Seedlings, with their tender new leaves, often give up the ghost when temperatures dip to 32-33°F. Tropical plants have differing low-temperature thresholds. Some keel over when temps fall to 40°F; others crumble at 35°F. Other plants are just hardy by nature and can withstand temperatures as low as 18-20°F.

Should I cover my plants at 39 degrees?

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.

Is 39 degrees too cold for annuals?

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.

Are plants safe at 40 degrees?

Some plants can survive outside even when temperatures hit freezing. Others need to be brought indoors when temperatures reach the mid-40s.

Is 39 too cold for tomato plants?

Another temperature to keep in mind: tomato plants will not survive in temperatures below 35 degrees Fahrenheit, and will not thrive at temperatures below 50 degrees.

Should I Cover My Plants At 39 Degrees

At what temperature should you cover your tomato plants at night?

It's sunny again… wait… ), but some vegetables won't be happy (and grow into incredibly prolific tomato producers - yes, I'm talking to you, tomato fanatics) if you don't protect them until night temperatures warm up consistently to 50 degrees and above.

What temperature is too cold for potted plants?

Most houseplants are native to tropical areas and will not tolerate freezing temperatures. Many indoor plants will see damage when temperatures drop to the mid to lower 40s°F and nearly all will die if exposed to below freezing temperatures.

What plants need to be covered at 40 degrees?

First, it's good to know which plants are sensitive to temps around 35 or 40 degrees F. These are common tender plants that will need some protection. Hanging baskets: begonias, calibrachoa, gerbera, impatiens, vinca, euphorbia, and scoparia.

Will cucumbers survive 40 degrees?

Cucumbers are heat-sensitive and do best in temperatures between 60-90°F (16-32°C). They can tolerate some heat but will become stressed if temperatures exceed 95°F (35°C). Cucumbers can also be damaged by frost and temperatures below 50°F (10°C).

What is the lowest temperature to leave plants outside?

There is no universal temperature for all plants that is too cold, so that is why it is important to do your research. However, it is safe to say if living in an environment with harsh winters and temperatures below 20°F, it is always wise to bring plants indoors during this time, if possible.

Will it frost at 39 degrees?

A local study done on frost formation relating temperature to dew point has these guidelines for frost: temperatures from 38 to 42 F can lead to patchy frost, 33 to 37 areas of frost, and 32 and below widespread frost/freeze.

Do I need to cover flowers at 38 degrees?

Once temperatures drop below 40°F, you may want to start covering your plants with a frost blanket depending on what you're growing, which we'll get into in just a bit. Freeze – A freeze is when the air temperature is 32°F or below.

What is the lowest temperature annuals can tolerate?

Focus on frost hardy annuals. Some of these annuals that can withstand 20 degrees or so, including pansies, snapdragons, dianthus, alyssum, dusty miller, viola, and osteospermum. Keep in mind that flowers may be a bit ragged after such cold but the plants should make it through ok.

What temperature is not safe for plants?

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.

Can plants survive one night of frost?

A light frost may cause minimal damage while a severe frost may kill plants. Young, vulnerable plants are much more susceptible to a light freeze, which occurs when temperatures are 29 to 32 degrees Fahrenheit, while mature plants may only suffer from short-term effects.

Is 41 too cold for annuals?

H2 Rating - 34 to 41° F (1 to 5 C)

Overall, these annuals are the most delicate of all the hardy annuals - one might call them half-hardy since they are really only hardy into the few temperatures just above freezing. And it's important to NOT let them freeze.

Are tomato plants ok at 40 degrees?

At temperatures below 40°F, tomato plants will begin to wilt and brown from chilling injury. At best, the plant will experience stunting, wilting, and pitting of fruit.

Is 40 degrees at night too cold for plants?

The trick is to make sure you protect these cold sensitive plants before they succumb to a killing frost or freezing temperatures. All tropicals can take the heat but most are highly sensitive to cold weather. For the most tender plants, temperatures in the 40's can do them in.

What is the lowest night temperature for cucumber plants?

Cucumbers are very tender, warm-season plants that grow best in temperatures from 65° to 75°F (18.3° to 23.9°C) with a minimum temperature of 60°F (15.6°C) and a maximum of 90°F (32.2°C).

Can peppers survive 40 degree nights?

So will peppers survive 40 degrees? To sum it up, most peppers won't necessarily DIE from 40˚ F temperatures, but their growth can be stunted, and they may be slow to recover so it's best to keep them warm if possible.

Should I bring my plants in at 38 degrees?

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.

Can zucchini survive 40 degree weather?

Zucchini is a warm-season crop that cannot tolerate frost or freezing temperatures, so its best to plant your zucchini in the early summer, when temperatures are at least 70 degrees Fahrenheit or more.

At what temperature should potted plants be brought inside?

Houseplants/tropicals need to come inside when night temperatures are below the low- to mid-50s or approximately one month before you normally turn on the heat in your house.

Can marigolds tolerate 40 degrees?

Marigolds can handle a bit of a chill, but they draw the line at frost. They can survive down to about 40°F, but it's not a party they enjoy. To prepare for cooler nights, especially in the unpredictable shoulder seasons of spring and fall, think like a marigold.

At what temperature should you cover your plants at night?

Cover Plants – Protect plants from all but the hardest freeze (28°F for five hours) by covering them with sheets, towels, blankets, cardboard or a tarp. You can also invert baskets, coolers or any container with a solid bottom over plants. Cover plants before dark to trap warmer air.

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