Plants native to the subtropics are in danger below 40 degrees F and pretty certainly going to be killed at 32 degrees F. Plants native to the tropics are often damaged below 50 degrees F and perish at about 40 degrees F.
40F won't hurt any of those plants but if the soil gets too cold they can all be affected. So if it's me I cover if I think the soil might get too cold too long. Most warm season crops I like to maintain 60F soil temp minimum.
Freeze Warning - This is issued when there is at least an 80% chance that the temperature will hit 32 degrees Fahrenheit or lower. Light freeze - 29° to 32° Fahrenheit will kill tender plants.
Know The Limits
The general rule of thumb is that most plants freeze when temperatures remain at 28°F for five hours. Of course, there are exceptions to this rule. Seedlings, with their tender new leaves, often give up the ghost when temperatures dip to 32-33°F.
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.
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. Watch the weather forecast and bring plants back indoors well before nighttime temperatures get too cold. Before bringing them inside, check for insects.
As soon as the minimum temperature for the plants is reached permanently, they can be moved out of their winter quarter. Mediterranean plants with sturdy leafs such as olive, laurel and oleander can already be put outside in the beginning of April if no permanent frosts are expected any more.
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.
Impatiens don't tolerate cold weather and will wilt and die once frost arrives. Don't plant impatiens outdoors until after the last frost of spring; it's best to wait until nighttime temperatures remain at 50ºF or higher.
It's safe to move your plants outside when the outdoor temperatures stay consistently above 50°F. Pay attention to the weather report. If nighttime temperatures are set to fall below 50°F, bring your plants in for the night. Bring them back outside when temperatures rise.
Will a covered porch protect plants from frost? Yes, it will provide partial protection from light ice and chilly winds. Uproot tender perennials — Tender perennials are plants that cannot withstand deep freeze (roots, bulbs, tubers, and corms).
Even if you're antsy and can't wait to see the pop of color outside the porch, DO NOT put the basket outside until temperatures are consistently above 50F (minimum!). Let the basket stay toasty warm here, or keep it in a bright sunny space in your home away from sudden drafts or temperature fluctuations.
Spray with Insecticidal Soap: Before bringing your plants indoors, thoroughly spray their leaves, stems, and trunks with insecticidal soap to eliminate any remaining pests. Allow the spray to dry thoroughly before bringing the plants inside.
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.
If you're looking for tips for protecting your plants from frost, avoid using garbage bags as plant covers. Trash bags are not the best protection against frost damage, primarily due to their material. Most garbage bags are made out of low-density polyethylene plastic.
Plants need to be transitioned indoors before the outside temperature starts dropping below 45 degrees Fahrenheit (7 degrees Celsius) at night.
Many newer cultivars are able to withstand hotter temperatures, but no petunias thrive in chilly temperatures. When spring temperatures dip below 40 degrees F, either cover your outdoor petunias with frost cloth or bring them indoors. Temperatures below freezing will kill them in a jiffy.
Answer: Plant impatiens outdoors after the danger of frost is past. It's usually safe to begin planting impatiens in late April in southern Iowa and mid-May in northern portions of the state.
Impatiens perform best in moist, well-drained soils in partial shade. Sites that receive 2 to 4 hours of filtered sun during the day or morning sun and afternoon shade are usually ideal. Impatiens can also be grown in heavy shade. However, plants will be taller and bloom less profusely in heavily shaded locations.
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.
Many tropical plants cannot survive temperatures below 40 degrees. If you cannot move your pots (with annual or perennial plants), or you have tender plants in the ground, cover your plants.
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.
In spring, apply a general liquid feed and increase watering. Plant out only once all danger of frost has passed, usually from late May. If growing geraniums as house plants, you can let the plant carry on flowering into autumn, even winter. Keep indoor geraniums away from radiators or open fires.
Many houseplants thrive outdoors during Minnesota's summers but do not perform well or may even die if exposed to chilly temperatures. Depending on the species, temperatures dipping below 45-50°F can cause damage. Here are some things to consider before you bring your houseplants back indoors.
If the surface of the soil is dry to the touch (or looks dry) water your plants. You may need to check your plants twice a day to see if they need water. Remember just because one pot needs water that doesn't mean they all do. Differences in pot and plant sizes will impact how quickly a pot dries out.