By Paul James
Winter can be a tough time for tropical houseplants. Light levels indoors are less intense. Humidity levels typically drop way below the comfort level of most plants. But perhaps most critically, folks tend to water and fertilize their houseplants in winter the same way they do throughout the rest of the year. And that’s a big boo-boo.
Because of the sun’s lower angle in winter, light levels indoors can drop a whopping 50%, so plan on moving plants closer to windows or to an area that gets more light (such as a southern or western exposure). Just make sure plant leaves don’t touch the glass. Also, consider cleaning you windows to maximize light transmission, dusting plant leaves so they can absorb all the light available, and rotating plants a quarter turn each week for even light distribution.
If your plants need more light than is naturally available, add artificial light in the form of standard fluorescent tubes or lights made specifically for growing plants, such as high output LEDs.
The majority of houseplants prefer humidity levels of around 50%, yet in most homes in winter humidity typically hovers around 10%. The most common sign of plant stress resulting from low humidity is browning on leaf margins. Spider mites might also rear their ugly heads.
The surest way to increase humidity is to mist plants often – at least once, maybe even twice a day. Placing plants on a tray filled with moist pebbles also works well. But the simplest and most effective solution is a small humidifier – Duh! Just run it once or twice a day for half an hour or so and your plants will love it. As a bonus, the higher the humidity, the less you’ll have to water.
Without a doubt, the most common cause of houseplant failure is overwatering, and the most common season for failure is winter. Here’s why.
During most of the year, houseplants are actively growing and therefore need regular watering. But growth slows down considerably in winter, so you need to adjust your watering schedule. In the case of most houseplants, it’s best to let the soil dry out almost completely before watering (exceptions would be ferns and citrus, which need steady moisture).
But exactly how do you know when to water? Just poke your finger two inches into the soil. If it’s dry, go ahead and water.
Again, because plants grow very slowly in winter, they don’t need much if any fertilizer. And applying fertilizer at a time when plants don’t need it is more than just a waste of money – it can also lead to burning of the roots and a buildup of salts in the soil.
Finally, and again because houseplants go partially dormant in winter, it’s best to hold off on repotting until spring, when active growth begins. That’s also when you should begin fertilizing again and watering more frequently.