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.
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.
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.
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.
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.
Plants need to be transitioned indoors before the outside temperature starts dropping below 45 degrees Fahrenheit (7 degrees Celsius) at night.
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.
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.
Starting in mid to late September, it is beneficial to watch the forecast and take note of forecasted low overnight temperatures. Once temperatures dip to the mid-30s °F, it will be necessary to take action by bringing plants indoors, covering plants, or utilizing cold frames and hoop tunnels.
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.
Most houseplants are tropicals and prefer temperatures between 65-75°F during the day and about 10 degrees cooler at night. For many plants, temperatures below 50°F can cause problems. Adjust thermostats to cater to your comfort, but remember your plants need some consideration.
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.
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.
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.
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.
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.
ACCLIMATING YOUR PLANTS TO The INDOORS
Avoid moving plants directly from outdoor conditions to the indoors as this can stress them. Instead, gradually acclimate them by placing them in a shaded or partially shaded area for a few days. Don't be alarmed if your plant drops some leaves soon after being brought indoors.
The best way to tell if your plants need water is to stick your finger about an inch into the potting mix—if it feels dry, break out the watering can. If you detect dampness, check back again in a day or two. For smaller houseplants, you can also pick up the whole container. If it feels light for its size, add water.
Follow the 50-50 rule: Bring houseplants inside 50 days before the first frost, or when temperatures are consistently around 50 degrees Fahrenheit.
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.
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.
“In nature, plants will naturally gather humidity from the air, creating dew drops which will freshen the plant leaves and remove dust,” she says. “This ultimately creates a better exchange of oxygen and moisture. Misting one to two times per week can refresh your plants and keep them happy and thriving.”
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.