David Robson Extension Educator, Springfield Extension Center, University of Illinois
Yard & Garden
Helpful Humidity Hints for Houseplants
Don’t kill your plants with over watering, add humidity
Houseplant success during the winter months is determined by proper sunlight, correct watering and the right humidity levels.
The first two, light and watering, are the easiest to manipulate. You can move plants closer to the window, further away, or provide supplementary light in some way, shape or form, usually by placing the plants under a lamp.
Once you learn that plants don’t suck up as much water during the winter, mainly due to the lack of sufficient light, you start to hold back. Of course, plants will tell you right away that you’re watering too much by dying. Over watering is often credited as the number one way houseplants fail to survive.
So, the next time you get a plant, you withhold the water until the plant starts wilting, and then you take it into the sink and give it a thorough flushing. The plants will usually perk up.
But then there’s humidity. It’s the bane of houseplants, and the curse of the well intentioned who can modify the light and the achieve grandeur with watering. Sooner or later, the ugly head of humidity, or more correctly, the “lack of humidity,” will make itself known.
Most houseplants are tropical in nature, even bulbs such as amaryllis. Essentially the cacti and succulents can tolerate lower humidity levels that usually occur once we fire up the furnaces and the forced air starts drying out the rooms.
Being tropical, most houseplants would prefer humidity levels above 50 percent. Being stuck in Illinois homes, they’re lucky if they get 20 percent humidity.
In response to our lack of appreciation on their part, many plants start to go limp, which causes us to over water and eventually kill them. Or, they start shedding some of their leaves, which makes us think that we aren’t giving them enough water, so we flood the soil, and eventually kill them.
Sometimes the plants will turn yellow or brown along the edges of the leaves. Then we take the plants into the shower or sink, give them a bath, unaware that the water is filling the pot, forcing all the air out of the soil around the roots, and guess what? Eventually killing them.
If you do nothing, the plants will look ratty, but will respond in the spring when the furnaces are turned off and the windows opened to let in the fresh air. All is good until we turn the air conditioner on, which also dries out the air.
We need to look at raising the humidity level, and really, it’s not that hard. There are some easy things to do.
First, you could add a humidifier to your furnace. Granted, that costs more money, and you’ll have to have an outlet for the excess water that drains from the furnace. But all in all, it’s the best course of action.
Next, you could add a room humidifier. These are great as long as you keep them filled. Most gardeners come to a quick realization that it makes more sense to put the humidifier in the room with the plants, or the plants in the room with the humidifier.
Another option is to group plants together. As the moisture escapes their leaves through the natural transpiration process, it does create a small humidity chamber around the plants. Unfortunately, it may not be as great as you think.
Setting the plants on trays filled with pebbles, and then adding water around the pebbles, is one of the best options for adding humidity. As the water evaporates from the trays, it adds humidity to the room, and especially around the plants. You just need to make sure the pots are sitting above the water, and not in it. Or eventually the plants will die.
The worst thing you can do is mist the plant with a spray bottle. It makes you feel good, but the water vapor doesn’t hang around the plant, any more than spraying perfume in one spot stays there. Eventually it dissipates everywhere.
If, after doing everything, the plants still seem to be listless and yellow, consider replacing them with cacti and succulents that can tolerate lower humidity.
David Robson is an Extension Educator, Horticulture, at the Springfield Extension Center, University of Illinois Extension, P.O. Box 8199, Springfield, IL 62791. Telephone: 217-782-6515.
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