| | How to increase humidity around your plants | Ventilation | Temperature
Humidity is an important factor affecting plant health. All plants, with the exception of cacti and succulents, require a fairly moist environment to function at their peak level, although many can tolerate low humidity. The average home is too dry to please most plants, especially if air conditioners or heating units are in use.
Relative humidity measures the amount of water vapor in the air compared with the amount the air could hold at a given temperature. As air warms, its moisture-holding capacity increases, and the relative humidity is lower.
As well as requiring a higher overall moisture content to maintain a certain humidity level, warm air increases the transpiration rate of plants. To lower their 'body' temperature, plants give off water through their leaves (transpire). This causes them to wilt on hot days. Furthermore, hot dry air provides the perfect environment for red spiders, thrips and scale insects.
Humidity levels of 40 to 60 per cent are ideal for human comfort and health. Greenhouses are maintained at higher levels (60 to 80 per cent). Experiments with tropical foliage plants have proven plants are at their healthiest when relative humidity is close to 70 per cent. You will find, though, plants can tolerate much lower levels. Certain hardy varieties (such as cactus, Sanseveria, the Bromeliads, Philodendron and Schefflera) will survive levels as low as 25 per cent.
Plants not receiving adequate humidity have dull, brown-tipped leaves and an unusually slow growth rate,
How to increase humidity around your plants:
- Large home-humidifiers, although expensive, can be adjusted to provide a controlled humidity level to suit you and your plants.
- Cover the bottom of a shallow tray with gravel or pebbles and fill with water. Set potted plants on the gravel, making sure the water level does not touch the bottom of the pots.
- Mist plants regularly with a fine spray of water. Any type of squirt bottle (such as those containing window cleaners) will serve the purpose; or special misters can be purchased at garden centers.
- Placing plants together is a simple way of raising the humidity around the plants. Each plant will benefit from the moisture given off by the others through transpiration.
- Laundry rooms, bathrooms and shelves close to the kitchen sink are all areas with high humidity levels.
- Terrariums and bottle gardens provide moist environments.
Ventilation
During the day, plants carry out photosynthesis, using carbon dioxide and producing oxygen. At night, when photosynthesis stops and respiration becomes the predominant activity, oxygen is consumed and carbon dioxide levels increase. This steady cycle enables plants to live in sealed containers with no source of fresh air. Nonetheless, air circulation is beneficial to plant health. Plants grown in overcrowded, or moist, stuffy conditions are highly susceptible to fungus disease. Greenhouses always have a large fan to circulate air; small fans are inexpensive and useful to the homeowner with a large collection of plants. The degree of ventilation required for each species is often given in plant catalogues.
Ventilation can be supplied by opening a window, but first ensure this will not subject plants to cold drafts. Most house plants will wilt or shed their leaves if exposed to cold air or drafts. Plants placed in doorways or major passage-ways in the home become ragged-looking and unthrifty; only the hardier types such as Sanseveria, Scheffiera, or the Bromeliads, should be chosen for these locations.
Temperature
Temperature requirements vary greatly from species to species. Before buying plants inquire about.their preferences and choose only those which you can accommodate in your home. You will find temperatures fluctuate between different areas with the home, making it possible to grow several plants with varying requirements. These fluctuations must also be considered when rearranging your house plants; a plant may suffer a setback simply because it has been moved to a different temperature zone.
In general, however, most house plants are satisfied with a constant room temperature between 180 and 21°C, with a night drop of 5°C. This temperature drop is necessary to give the plant a chance to conserve food produced during the day, by slowing the rate of respiration (the process by which a plant utilizes the sugars it has produced through photo-synthesis).
Do not leave plants too close to a window in winter without some protection, such as a layer of newspaper or a curtain. If a plant has become chilled, sprinkle it with cool water and place it in a cool cellar. Cut the plant back to a healthy bud, to allow it to develop new, strong growth.
Adapted from Agdex 285/20-5. |
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