It is often said that over-watering is the number one killer of houseplants. On the other hand, depriving them completely of water will have the same disastrous result. Understanding the appropriate amount of water to give to your plants can be confusing. Some people consider it a simple matter and water their houseplants whenever they think of it while others may water once or twice a week regardless of their plants’ needs. Neither of these methods is best for the plants.
Just what is the proper way to water indoor plants? Houseplant specialists recommend that the plants themselves be carefully observed to determine watering frequency. It’s important to catch them before there is any sign of wilting, but soil that is kept wet all the time encourages root rot. Learn to read the signals that your plants need water. The color of the foliage may fade, and the leaves of succulent plants become limp and rubbery. Lift the pot; the container feels lighter as the moisture evaporates, particularly if you are using some of the newer soil-less houseplant potting mixes. The potting mixture will also feel dry to the touch. Push your finger into the soil to feel if there is moisture under the surface. The surface of the soil may be dry even if there is sufficient moisture around the root ball.
The important thing to remember is that each type of houseplant has its own particular water requirements. The watering frequency will be influenced by the type of leaves, the age of the plant, the temperature and humidity of the environment, the type of potting medium and the amount of light the plant receives. Plants with waxy or leathery leaves like the rubber plant, ponytail palm or jade plant can go a longer period of time between each watering, while plants with thin leaves like Boston ferns will require watering more often. It is important to avoid swings from extremely dry to extremely wet soil.
Regardless of the type of plant, it is important that the soil ball be completely soaked with each watering. Apply water until it runs from the drainage holes in the pot and then after a few minutes, empty the water from the saucer or tray under the pot. If the plant is allowed to sit in the water, it will be absorbed up into the soil ball causing it to become waterlogged, often resulting in root rot. If the container is too large to easily lift off its tray, use a turkey baster to siphon off the excess water.
It is important that the containers or pots have drainage holes so that water can drain from the soil freely. Layering pebbles or charcoal in the bottom of a solid container does not help soil drainage. If you wish to use a decorative container without drainage holes, it is best to double-pot the plant by setting a pot with drainage holes inside the container.
Most plants have no problem with city water. If possible, avoid using softened water for plants as the chemical salts will eventually build up and injure the roots. Avoid using icy cold water for plants. Most of the houseplants we grow originated in the tropics or sub-tropics where rainfall is relatively warm. Ice cold water will cause root shock, which may lead to permanent root damage, leaf drop and other problems. Allow the water to warm to room temperature before watering the plants.
In summary, treat each all your plants as individuals, learn to read the signals for watering frequency, and water them well using room temperature water as needed.
Complete Guide to Houseplants, Ortho, 2004.
The Complete Houseplant Survival Manual , Barbara Pleasant, Storey Publishing, 2005.
Indoor Plants, Cynthia Haynes, Iowa State University Extension, 2005.
Master Gardener Program University of Minnesota 952-443-1442 or www.extension.umn.edu/garden/master-gardener/