High Humidity Helps Houseplants

We may sometimes be disappointed to find that after having beautiful houseplants in our homes for a week or two, the tips and edges of leaves begin to turn brown. This condition often develops because the plants are now growing in a lower humidity than previously. Some plants we normally grow in the home come from the tropics, where humidities may run close to 90 per cent.

Others come from the subtropics, where humidities may fall between 50 and 60 percent. Desert climates may run as low as 5 percent, and occasionally in winter the humidities in homes come close to this. Generally, the humidity in a heated home in winter runs around 20 per cent, which is too low for good growth of many houseplants. Humidity is relative, it is the capacity of air to absorb moisture in relation to the temperature.

If the temperature outdoors is 30 degrees, the relative humidity may be 50 per cent, which would be good for many plants. When this same air is heated to 70 degrees indoors, however, the relative humidity drops to a level much less satisfactory for plant growth. The relative humidity in a cool spot or on a cool window in a room is higher than the humidity in a warm spot of the same room. The worst location for plants indoors is close to a hot-air vent.

There are several ways to increase humidity around house plants. One of the simplest is keeping a tray of damp pebbles beneath plants. Moisture evaporates constantly from the stones to keep up humidity around the foliage. Watertight metal trays or large saucers are attractive and easy to use. If none are available or are too expensive, build a simple wooden frame to fit the boundary of the area in which plants are kept. Line it with a sheet of heavy plastic film.

If care is taken that no holes are punched into the plastic, it will be watertight and can be tacked to the top of the frame to make a good water reservoir. Carefully add gravel to the tray so the plastic is not torn. Other inert materials such as perlite may also be used to fill the tray. Keep water in the tray at all times. The base of each pot should be kept on the surface of the material in the tray. The water level in the tray should always be well below the top of the layer of material.

Spraying over plants is another way to increase humidity. To be most effective, it should be done daily, preferably several times a day. If there are many plants, it is easier and quicker to use an electric sprayer. For just a few plants, a hand sprayer or atomizer works well. Use a very fine spray, and mist over the foliage so that only fine droplets settle on foliage. Do not wet foliage so that water drips from it. Plants that require a very high humidity such as orchids, benefit from both the pebble-filled trays and misting.

Humidifiers also increase plant humidity. In a big room, a large humidifier is needed to do a good job. Although it must be kept filled, there is less labor involved than frequent spraying. By placing plants close together, a higher humidity is maintained around them. Dense foliage keeps humidity up. Do not pack plants so tightly, however, that they are shaded from adequate light.

http://gardenline.usask.ca/plants/humidity.html