Fortunately, many house plants thrive in average humidity levels within a home - with little attention paid to improving the levels.
However, certain plant species (especially those native to the tropics and sub-tropics) need higher humidity levels, while others such as cacti and succulents respond well to dry conditions.
One of the biggest problems plants encounter (regarding humidity) growing indoors is enduring weeks or months in a room with central heating or any other artificial means of heating.
The good news is we can prevent or rectify humidity problems by knowing the plants care needs, and improving house plants humidity levels.
The measurement used for humidity is what’s called relative humidity, which measures water vapor and a specific amount air relative to the number of water particles that could be in a certain amount of air.
Relative humidity is used to help determine a comfortable level suitable for animals , humans and plants. For more info on the science of humidity take a look at the wiki article here.
80% - 90%: This is tropical weather that were not likely to encounter in temperate regions. Plants growing in a greenhouse or glasshouse can reach above 80%. For some species its the best place for them to grow.
60% - 80%: This is the ideal level which is difficult to maintain indoors, especially for tropical plants. If a plant is sensitive to lower levels than 70%, increasing the humidity will be required.
60% - 40%: You'll find most homes are about this level during the summer which the majority of plants thrive in. Certain plants will need some assistance, which may only be misting.
10% - 40%: Below 40% is becoming very dry and is likely to be the levels indoors when central and artificial heating is being used. Your cacti and succulents will be fine but the majority of plants are going to have leaf and flower problems.
A useful device is a hygrometer which measures the relative humidity levels that are relatively inexpensive.BUY HERE »
Basically: The higher the temperature and smaller the amount of water vapor - the lower the humidity. And, the lower the temperature with a higher amount of water vapor the higher the humidity. Although, this works based on the amount of each with an amount of air.
Succulents and desert type cactus plants have fleshy thick leaves which store water that allows them to survive in dry conditions for a period of time. These plants survive well below 30% relative humidity.
There are common signs to watch out for that can be the cause of low or high humidity, although other causes will also have to be examined (i.e., bright light, over-watering etc.) which can have a similar affect on plants.
1) Misting - Misting the leaves with a fine misting spray bottle and tepid water is a common and effective method.
2) Grouping Plants - When plants are placed together in groups they kind of act in the same way as forest trees and plants act, which is to trap air and moisture between each of them. They can also use each others moisture from the soil. When doing this allow some space between each of the plants.
3) Pebble/Gravel Trays - A great way to improve humidity is to place plants on a humidity tray. This tray consist of small pebbles or gravel covered in water. The water has to be just below the top of the pebbles or gravel so the plant does not soak up any water and remains well aerated. You may want to purchase a humidity tray specifically for plants, which are inexpensive.
4) Humidifier or Dehumidifier - Some rooms indoors need a de-humidifier or dehumidifier for our own comfort and these can be bought to improve the humidity for plants also.
Additional methods which improve humidity is to place containers with water in a room. Have a vase with flowers filled with water which is an attractive way of doing this or having a decorative water feature. Having bromeliads within a room is another opportunity to provide the air with more water because they store water in the vase part of the plant.