Regional Gardening Reports :: National Gardening Association

In the Garden:
Northern & Central Midwest
January, 2008
Regional Report

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These healthy houseplants benefit from the increased humidity created by snuggling together, and the moss mulch helps conserve moisture, too.

Raise the Humidity

Those of us in the Midwest have been heating our houses for several months now, and this is the time of the winter when houseplants tend to look their worst. They've been in the same dry air that makes our skin itch and our noses raw. They, too, need humidity to keep their tissues healthy.

Humidity is defined as the percentage of water in the air. Warm air holds more moisture than cold air, but furnaces also tend to dry out the air. A plant that comes from a naturally humid climate needs some assistance from us to get extra humidity when our homes are dry. There are several effective methods, varying in the amount of work necessary to put them together, and in cost.

The classic sign of too little humidity is browned leaf tips and margins. On the flip side, too much moisture in the air can increase fungal diseases. You want to find a balance and add enough moisture to keep plants healthy and also keep some air circulating to prevent disease.

Adding Moisture to the Air
The most efficient way to raise humidity is by installing a humidifier directly on the furnace. This will raise the humidity throughout the house, but it may not necessarily create a humid enough environment for certain plants. And it's an expensive choice.

A room humidifier placed near certain plants will usually provide what they need, and it just takes routine maintenance such as filling and cleaning.

A simpler way to increase humidity is to group plants together. This keeps the ambient humidity around the group higher than if each plant were on its own. But it reduces some of the air circulation around them.

Another option is to place the plant's pot on a tray of pebbles or shells that are kept moist. It's important not to sink the pot into the pebbles as this will keep the soil soggy. Fill a plant saucer with decorative stones, fill the saucer with water, and place the pot on top. The water will gradually evaporate and put some moisture into the air.

The pot-in-pot method also works. Simply place the potted plant in another decorative pot a couple of inches larger in diameter, and fill the cavity between them with sphagnum or Spanish moss. Keeping the moss damp will allow natural evaporation up around the plant. Be sure to elevate the interior pot so it does not sit in water.

Adding mulch to the soil of your potted plants can help add humidity, keep the soil more moist, and be decorative, as well. Mulches range from stones, sphagnum, sheet or Spanish moss, and shredded bark. Ground cover plants used in the pots of larger plants can function as living mulch. Just make sure the ground cover plant requires the same cultural conditions as the larger plant.

Hold the Mister
Often you will see a recommendation to hand mist the foliage of plants that need high humidity, but in actuality this method is seldom successful and can cause problems. Mist on leaves evaporates very quickly, so you would have to do it continually to have an effect. And wet leaves can be an invitation to fungal disease.

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