Preparing Houseplants for Winter

Winter is difficult for houseplants and they’ll need a bit of TLC to get through it. Source: www.mygardenlife.com

There are so many reasons why we should all have plants in our homes: they beautify our decor, filter the air of pollutants, add beneficial moisture to the air, reduce the frequency and duration of colds and flu, increase the oxygen level in our homes, etc. But still, you do have to keep them alive …and winter is the most difficult time of the year for houseplants, at least, if you live outside of the tropics.

Fall and winter conditions simply make life hard for indoor plants. Shorter and grayer days seriously reduce the sunlight they receive and therefore their ability to grow, plus the dry air present in our homes during the heating season can damage plants or even cause them to drop their leaves. How then to prepare our houseplants for the harsh conditions to come?

The More Light the Better

To help make up for the short gray days of winter, place your plants closer to the window, even moving them to a more brightly lit room. Think too that large windows let in more light than small ones. Leave blinds and curtains open during the daylight hours and clean the windows (dust and grime greatly reduce the penetration of light). If possible, remove window screens, not needed in winter when insects are absent, as they too reduce amount of the light that penetrates. From the end of October through March, the sun in northern regions is unlikely to be strong enough to burn plants, even if you place them directly in front of a south-facing window.

It is also possible to use artificial lighting, including fluorescent lamps, to increase the day length. A simple two-tube workshop-type fluorescent lamp (combine a Cool White tube and a Warm White tube to ensure excellent light quality)—with a timer set at 14 to 16 hours a day and hung 1 foot (30 cm) above the plants—can even allow many houseplants to grow throughout the winter as if it were summer. There are now LED lamps that provide similar lighting.

Increase Atmospheric Humidity

Did you know that the relative humidity of a home heated in very cold weather can drop to 15% or less? That means the air is drier than in the Sahara Desert, where 25% is the usual minimum! And that most plants need a relative humidity of at least 50% to grow well?

To correct the problem, run a humidifier in the room where you grow your plants. Or group plants together, putting those with the thinnest leaves (more sensitive to dry air than those with thick leaves) in the center and the others all around. Since each plant gives off moisture due to transpiration, all the plants will benefit from increased humidity, especially the more fragile plants in the center.

Or, prepare a humidity tray. To do so, fill a waterproof tray with stones or gravel and place your plants on it, without a saucer (not needed, as the tray will catch any excess water). Now, when you water, pour extra water into the tray. The purpose is not to cover the stones in water (you don’t want the bottom of the pots to be left soaking!), but simply enough that the base of the stones sits in water at all times. Water will then move up onto the stones by capillary action and evaporate, offering your plants beneficial humid air.

On the other hand, spraying the plants manually with water, which you often see recommended, is a waste of time: the effect lasts only a few minutes, not enough for plants to benefit. To help them, the air needs to remain humid at all times.

Less Fertilizer

It’s never a good idea to try and encourage plant growth when light is weak: that will stimulate etiolation, a situation where plants seem to stretch towards the light with unusually long stems and pale green leaves. That’s not healthy growth and you don’t want to encourage it. So, stop fertilizing your plants in October to slow them downand only resume in March (in the Northern Hemisphere) when days begin to seriously lengthen.

If you use artificial lighting, however, most plants will continue to grow normally right through the winter and therefore you can continue your regular fertilization program.

Water as Needed

Sometimes you hear the advice to water houseplants less during the winter than in the summer. And that would seem to make sense, because isn’t it true that their growth slows down in winter? True enough, but the bulk of the water that the plants absorb is not used for growth, but rather is lost to transpiration…and plants transpire more when the air is dry, that is, in winter. Depending on your conditions (and especially on whether or not you’ve done something to increase air humidity), some plants may need actually more frequent watering in winter than in summer!

There is only one way to find out: check each plant once every four or five days by inserting your index finger into the potting mix to the second joint. If the soil is dry, water abundantly, otherwise wait another four or five days and try again.

Temperature: Usually Not a Problem

Tropical plants (and most houseplants are of tropical origin) prefer fairly warm temperatures year-round, at least during the day. At night, however, they do appreciate a good drop, to 60 ° F (15 ° C) or even less. And a nighttime drop in temperature is good for humans too. So, set the thermostat to ensure a nighttime drop or crack the window open a little at night.

Then, of course, there are the exceptions: houseplants that prefer cool temperatures day and (especially) night during the winter. This group includes most cacti (but not other succulents), cyclamens, azaleas, chrysanthemums, rosemary, Norfolk pine, etc. If you can find these plants a cool spot where they can pass the winter (about 60 ° F [15 ° C] during the day and 40 ° F [5 ° C] at night), they’ll appreciate it.

Never place your plants so close to a window that their foliage touches the glass or it may freeze. And avoid gusts of cold air, especially near doors that open and close in the winter.

Put Off Potting and Taking Cuttings

In October, when most houseplants are still growing at least somewhat, it’s still reasonable to repot houseplants or to take cuttings, but between November and February (in the northern hemisphere), it’s best to abstain. Since their growth will have slowed down or even stopped altogether, they won’t recover as readily from disturbances to their roots (repotting) while the cuttings tend to rot rather than to take root.

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There you go! Given reasonable care, your houseplants will spend the winter in fine condition and will be more beautiful than ever when spring comes around again!