How to keep your houseplants happy through a New England winter

New England weather is home to extremes, like increasingly hot summers and winters with brutal cold snaps. That whiplash is hard on houseplants, many of which are tropical and thrive in warm, humid climates with lots of light.

"The East Coast is one of the most challenging spaces to care for plants, for tropical plants specifically," said Julio César Román, owner of Micro Plant Studio in South Boston. "And the reason is because of the shift from AC to heater — and from the outside elements."

Here's what two local experts say you can do to keep your plants going through the gray days of fall and winter.

Has your plant stopped growing? Or is it dropping a few leaves? Don't fret.

"Just like how bears kind of go to sleep — they go dormant over the winter and kind of colder months — you'll find the same goes for plants," said Weslie Etienne Pierre, owner of Wesleaf Designs and Decor, a plant shop and design business in Needham.

Plants photosynthesize less with less sunlight to absorb. That also means they can make do without as much water and fertilizer, said Pierre. Cactuses, for example, can go more than a month without water in the winter, said Román.

If you want to prevent plants from going dormant in the winter, you'll need to keep your house warm and a bit humid. Install grow lights to mimic the brightness and warmth of natural sunlight.

When your plants are struggling, they send you signals, said Román. Yellow leaves can be a sign you're overwatering or under-watering your plant, or that they need a change in light.

"Should you go under panic mode? No, but be more proactive and figure out why is it responding the way it is," said Román.

It can be hard to tell exactly what a plant is trying to tell you, he said, but if tropical plants start to droop, that's a sign of under-watering. Or, if you're under-watering a pothos plant, you may notice yellowing of the lower leaves. That's because the plants are supposed to draw water from the roots but are now pulling it from the lower leaves, causing them to yellow, Román said.

If your hand feels cold touching the window pane, your plant's leaves will get too cold there, too. The cells in chilly leaves can die and turn brown, said Román. Try moving your plant about two feet back from the window, he suggests.

Old New England homes can be drafty. To keep drafts at bay, put rolled-up towels at the site of a draft or use a shrink wrap window insulation kit to keep the cool air out.

But in your effort to keep plants warm, be careful not to put them directly under a heater, said Román. The hot, dry air can burn leaves and cause the soil to dry out much more quickly. Wipe down your plants to prevent dust from heating systems from accumulating on the leaves. This will also help plants photosynthesize, so any sunlight does not get blocked by dust.

Because the plants have slowed down, the energy they produce is focused on just keeping themselves alive. Don't make big changes to the plant during the winter.

"You don't want the energy to go into recovery mode of the plant," said Román. "Propagation and repotting is best during the fall, unless you have the right environment."

Román suggests repotting plants from April to September.

If your plant lives outside in the warm months but comes inside in the winter, you could be bringing pests inside. Pierre says before you take plants indoors, drown the root system.

"That's bringing out the hose and really just filling up the root ball and letting anything that's taken shelter within your plant, letting them know it's time to move out," said Pierre.

Other bugs, like small red spider mites, thrive in the warm and dry environments created by home heaters. A humidifier can discourage them from sticking around.

Some common pests are easy to miss, as they're often tiny or experts at camouflage. Mealybugs, for example, are teeny white nuisances that infest indoor plants. Gnats are black with wings and lay their larva in the soil, making them tricky to get rid of. If you start to see little yellow circles on your plant's leaves, that could mean bugs are chowing down on the plant.

If you do notice pests, Pierre suggests spraying plants with a one-to-one mixture of rubbing alcohol and water.

While buying up houseplants may feel like a spring activity, it's still OK to purchase them in the winter. But there are a few things to keep in mind.

Plants sold in the winter are likely coming to New England stores from Florida and have been in transit or on store shelves for a while, said Pierre. Even if the leaves look healthy, you'll want to do a more thorough inspection.

"Sometimes I will shimmy the plant out of the pot, look at the roots, see if they're healthy and juicy," said Pierre. "If they're not, that's not a plant you want to buy."

If you find a good plant, take it right home in a warm car. Even short bursts of time in freezing air can damage tropical houseplants. Pierre suggests bringing insulated bags or towels to keep the plant toasty in a cool car.

Once you get your plant home, keep it away from your other plants for about two weeks. You want to prevent any pests on your new plant from spreading to your existing houseplants. Make sure to wipe down the plant and spray with the rubbing alcohol-water mixture to kill any bugs hiding in the leaves.