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.
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.
When do I know it's safe to bring my plant outside? 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.
That all depends on what plants you're growing indoors. Some like cooler temperatures and others prefer more warmth, but since most houseplants are tropical, a good rule of thumb is to keep them somewhere between 60 and 75 degrees F.
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.
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.
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.
This is usually about four to six weeks before the average first frost in your area. A couple of weeks before the temperatures dip to 50 degrees or below, put your potted plants underneath a tree or onto a covered porch so they can start adjusting to the reduced light they'll get in your home.
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.
Time It Right
While it might be tempting to ship indoor plants outside at the first sign of spring, it's best to wait until nighttime temperatures stay at or above 60°F, and after any threat of frost has passed. If you're planning ahead, use the average last frost date for your area as your guide.
Plan to bring in your houseplants when temperatures are forecast below 45 degrees F to protect them from stress and cold damage. Tender perennial herbs like Rosemary or Lemon Verbena can be brought indoors as well for winter cooking.
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.
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. The idea behind covering plants is to trap the heat from the soil and keep the cold air out.
When you move them outside, it's important not to move them into too much light. Even the brightest indoor locations are only a fraction of the light intensity compared to any shady spot outside. Houseplants will do best if they "vacation" in a full-shade or part-shade location outdoors.
Giving your plant a good rinse is a good way to remove dust, dirt, and any bugs that might be hanging on before bringing it into your home. This is also a good time to give your plant a deep watering. Consider the plant's needs when placing them indoors.
A Basic Recipe for using soap as a pesticide:
Use a mild dishwashing liquid or Castille Soap. Natural Hand soap can be used too. Add 1 tsp of dishwashing liquid soap to 1 Litre of water. Place in a spray bottle and gently spits your houseplant, covering the top and bottom of the leaves.
“Spritzing your plants is not the correct way to water your plants. In fact, it doesn't water them at all,” she says. While spritzing can provide some moisture, unless the plant really thrives in humidity (ferns, orchids, or bromeliads, for example), Hovis says spritzing can do more harm than good.
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.
Some experts recommend bathing or soaking plants in a bucket of water with mild dishwashing soap before bringing them inside. If your plants are too big for the bucket treatment, spray them with water to remove outdoor dust and soft-bodied insects from the leaves.
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.
Follow the 50-50 rule: Bring houseplants inside 50 days before the first frost, or when temperatures are consistently around 50 degrees Fahrenheit.
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.