Garden catalogs are inspiring and books and films set in Tuscany or Mexico a welcome respite but, really, nothing gets a gardener through the winter like an array of houseplants. When I moved into our first little cabin in Vermont’s Northeast Kingdom, while the 16-by-20-foot living quarters left scant floor space for a family with two active children and a cat, there was a row of south-facing floor-to-ceiling windows that quickly became a jungle of plants. The snow often fell from October to April and temperatures regularly plummeted to 20 below zero outside, but inside potted palms, angel-wing begonias, rosary vines and spider plants twined down and clambered up in a curtain of green. Until, that is, I went away for a week and the thermocouple on my gas furnace fizzled out. I returned home to a perfectly preserved frozen wonderland of houseplants that, once thawed, made a one-way trip to the compost. I was so traumatized I never replaced the plants and for many years held myself to moving a few pots of geraniums from front stoop to said windows in seasonal rotation. 

Below-freezing temperatures are clearly too much of a good thing when it comes to houseplants, but cooler temperatures are one way to make your indoor garden flourish. when I returned home after a week away over the New Year’s holiday I was surprised to see that paperwhites I’d started for Christmas were still holding their blossoms and plants that looked a bit tired and weary had perked up. They all had benefited from a spartan 50-degree thermostat setting. While daytime temperatures were considerably warmer, the plants loved the cool nights. This temperature variance mimics the conditions plants experience outdoors in the course of a 24-hour period, and they seem to get a new lease on life if their nights are a bit chilly. 

Less heat also means higher humidity, but even lowering the thermostat won’t give your houseplants the 50- to 60- percent humidity level they like. Inside, humidity levels in a Maine home in January can drop below 35 percent. Setting your plants on humidity trays is one way to add moisture to the air. In a low-sided tray, plastic or metal, place a shallow layer of pebbles. Add water to the height of the pebbles. Set your plant pots on the pebbles and put the tray in a warm, sunny spot. The trays also catch any dribbles or spills when you water. If you want to make your plants really happy, give them a little spritz from a mister every few days.

Oddly enough, although your houseplants do better in humid air, they need less watering in the winter months. Most plants only need water once a week in winter, as they almost go dormant, especially if they’re plants you’ve moved in from outdoors and they experience the transition from bright light to lower lighting and lower temperatures. This period of slower growth means that plants don’t need to be fertilized either. Wait until spring to start feeding your plants.

It almost goes without saying that your houseplants deserve the sunniest spot in the room. The best location is an east-facing window that gets sun from 7 to 11 a.m., not the harsh light found in a west-facing window. Sometimes, however, a plant will be even happier in indirect light, so don’t hesitate to move your plants around to see where they do best. 

In order to take advantage of available sunlight, your plants need clean leaves. When a leaf becomes dusty, its pores, called stomata, become plugged and photosynthesis will be slowed. Smaller plants can be washed in the sink with a gentle sprayer. Larger plants can go into the shower. Wipe leaves with a damp sponge afterwards so they don’t drip all over the floor.

There comes a time in almost every houseplant’s life when it needs repotting. Signs that a plant is pot-bound include potting mix drying out quickly even during periods of cooler temperatures, roots growing through the drainage holes, and slowed growth even if the plant is fertilized regularly in spring and summer. The best time to repot is in the spring so that actively growing roots will have enough time to grow into newly added potting mix, so if you see any of these signs, in early spring, remove the plant from its container and examine the roots. If they’re circling around the root ball or are so dense that it is difficult to see any potting mix in the bottom third of the root ball, it’s time to repot.

 At this point you need to choose whether to let your plant  grow larger or keep it at its current size. If you don’t want a larger plant, remove the outer section of plant roots, return the rootball to the container with some new potting mix, and cut back some of the plant’s top growth. If you want to let the plant grow larger, spend some time selecting a suitably handsome replacement pot, as it could be around for many years. After you choose an appropriate container and potting mix, water the plant in its original container and let it sit for an hour before repotting. If you have a new plastic or glazed container, no preparation is necessary, but a new clay container should be soaked overnight in water. If your container has drainage holes, place a few pieces of a broken clay container over the hole. This will allow excess water to drain through the hole, but prevents potting mix from doing so. Next, remove the plant and gently tease the tangled roots out from the rootball. Place enough potting mix in the container so that the top of the rootball is slightly below the lip of the new pot, then add more potting mix around the rootball and gently firm it in place. Leave an inch of space between the potting mix and the top of the container so that there is room for water and additional plant growth. Finally, water the plant and place it back in its preferred location.