Even houseplants deserve a summer vacation, and many homeowners indulge their plants with a warm-weather visit to the patio or deck. But summer doesn't last forever, so keep those plants in mind as autumn comes around and the outdoor nighttime temperatures drop. At some point, your houseplants will need to come in before they suffer damage from the cold, and that point may be well above freezing.
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Want to know when to bring your plants inside? Here's some advice on when to do it and how to ensure your houseplants stay healthy for the cool-weather season.
Experts recommend that you bring your plants indoors when nighttime temperatures drop to 45 or 50 degrees Fahrenheit. But it may be better to act well before that, when indoor and outdoor temperatures are about the same.
The Best Time to Bring Plants Indoors
The ideal time for bringing houseplants back indoors is when indoor and outdoor temperatures are about the same. This roughly happens in late summer rather than fall for most locations. If moved before or after this optimal outside temperature, the plants can suffer shock from the sharp differences between outdoor and indoor conditions.
Beyond waiting for the right temperature, knowing how to move plants indoors correctly is also important. If your houseplants have been in full sun, they should move inside to a south-facing window or be placed under a grow light. If they have been in dappled light outside, try a west-facing window placement. Shade-loving plants may do best in front of east-facing windows. To make sure all of the leaves get sun exposure, experts recommend turning the pot one-quarter turn every time you water.
What Temperature Is Too Cold?
When it comes to houseplants, some like it hot (especially plants originating in the tropics like Hibiscus rosa-sinensis), but almost all plants need it to be at least warm. So, what is the cutoff temperature for indoor plants spending the summer outdoors?
The critical temperature for which to watch is 45 degrees Fahrenheit. All houseplants living outside for the summer need to be brought back indoors before overnight temperatures dip below 45 degrees. Tropical plants may suffer harm even before this, so bring them inside a bit earlier, when temperatures drop below 50 degrees. Another way to schedule the return of houseplants is to bring them in for winter two or three weeks before your average first frost date.
Check for Bugs Before You Move Indoors
While you may be anxious to have your houseplants back in their traditional pots indoors, you don't want them to bring insect pests — like mealybugs, aphids, or broad mites — or diseases into the house. Before moving your plants indoors, it's a good idea to check them for insects and do a proper debugging first.
Start with a visual check of each side of each leaf and inspect the stems, pots, and saucers for evidence of infestations. Wipe away any webbing, bumps, or bugs. Then, soak the entire plant, pot and all, in a tub of lukewarm water with mild dish soap for about 15 to 20 minutes. This will kill any insects that are on the plant or in the soil. Take the pot out of the water and let it drain completely. Let the potting soil dry out thoroughly before you water it again. An alternative to soaking is to spray the foliage with insecticidal soap.
Check for Damage
If the entire plant seems to be wilting, it might be suffering from root rot. This is almost always caused by a combination of overwatering and poor drainage. Take the time to repot the plant in a container with ample drainage holes (and if your plant has grown significantly, this may be a good idea to upgrade to a larger container). Add sand to the fresh soil if necessary to make sure the water drains thoroughly. If sections of the roots look soggy, cut these off, leaving only healthy roots.
Chilly weather and cold winds can turn leaves yellow. Prune the affected leaves with sanitized pruning shears and immediately transfer the plant indoors. If there has been a freeze, you'll see even more damage. Frost damage turns leaves brown or black and can make them soggy, while stems can wilt, turn mushy, or collapse. They may look awful, but don't give up on them becoming healthy plants. Clip off damaged leaves and stems and site the plant indoors in indirect light. Keep the soil slightly moist and wait to see if new growth develops.
From Alaska to California, from France's Basque Country to Mexico's Pacific Coast, Teo Spengler has dug the soil, planted seeds and helped trees, flowers and veggies thrive. A professional writer and consummate gardener, Spengler has written about home and garden for Gardening Know How, San Francisco Chronicle, Gardening Guide and Go Banking Rates. She earned a BA from U.C. Santa Cruz, a law degree from U.C. Berkeley's Boalt Hall, and an MA and MFA from San Francisco State. She currently divides her life between San Francisco and southwestern France.