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Thursday, April 06, 2006

Watering Your Houseplants

Many houseplants suffer from too much or too little water. Often people want to adhere to a schedule, but this usually does not work. Several factors influence the frequency of watering, including type of plant, temperature, humidity, light, pot size, plant size, potting mix and drainage. The best method for determining when to water is to test the soil with your finger to a depth of two inches. If the soil is dry, it probably needs to be watered. Check your plant regularly. Wilting plants often indicate they need water, but sometimes it can be a symptom of over-watering. A water meter probe can be useful, but may not always be reliable.


Houseplants are probably killed or injured more often by improper watering than by any other single factor. No general schedule can be used for watering all houseplants. Size of plant, pot, light, temperature, humidity and other conditions influence the speed with which the soil mass dries out.

When to water
In general, flowering plants need more water than foliage plants of the same size. Never allow plants to wilt, and never water any plant unless it needs it. Soil kept either too wet or too dry causes plant roots to die, which leads to poor growth or death of the plant. Allow them to stand in water for long periods of time.

Learn to gauge the moisture content of the soil by its color and feel. As the soil surface dries it becomes lighter. Under continued drying, the soil begins to crack and pull away from the sides of the pot. When severe drying occurs, some damage already will have been done to the roots. Soil kept too moist becomes sticky and slimy, thus inviting root rots and other disease problems.

Kinds of water

Ordinary tap or well water is usually satisfactory for plants. Chlorine and fluorine often added to city water do not harm plants. Rain water or melted snow are excellent. Water run through most water softeners, however, should not be used continuously for watering potted plants.

How to water
Plants may be watered from either the top or the bottom of the pot. If you prefer watering from the top, use a watering can with a small spout and keep as much water off the foliage as possible. Each time, wet the entire soil mass, not just the top inch. Add water until it comes through the drainage hole in the bottom of the pot. Discard water that remains beneath the pot one hour after watering.

Watering from the bottom ensures thorough wetting of the soil mass. Place the pot in a pan or saucer filled with water, or dunk the pot in a bucket of deep water (just below the rim of the pot). When the top of the soil becomes moist, the entire soil ball should be wet. Remove the pot, allow it to drain and return it to the saucer.

Salts may form a white accumulation on the soil surface if plants are watered regularly from the bottom. Occasional watering from the top helps wash out the salts. Don't allow the soil to reabsorb any water that has been run through the soil to leach out salts. Surface salt accumulation may become too heavy to remove in this way. When this happens, scrape off the surface soil and replace it with fresh soil. Try not to injure plant roots.

Potted plants should always have good drainage. Occasionally the drainage hole may become clogged by roots. Check it by pushing a finger, stick or pencil into it. Even though drainage from the pot may be good, pot coverings may hold water. Pots wrapped in waterproof foil or placed in deep planters should be checked occasionally for standing water.

Plants with "wet feet" soon look sick -- leaves yellow or drop, flowers collapse and normally healthy white roots turn brown. Any or all of these can result from stagnation of the water, too little soil oxygen and development of diseases which rot the roots.

If you choose to water from the top, be sure to soak the soil thoroughly and allow the excess water to drain through to the saucer. Then empty the saucer. Do n

ot allow the pot to sit in a saucer of water.

Another method is sub-irrigation. You can place the pot in a few inches of water in a sink or in a saucer. Remove the pot when the moisture has wicked upward through the soil, and it is evident at the top.

Water Absorbers

Water absorbing polymers can be added to the potting mix prior to planting to help improve water-holding capacity. This can be useful for plants that have a high watering requirement, or for maintaining plants growing in difficult-to-reach locations. Follow the package directions carefully. Too much or too little will yield disappointing results.

Other Watering Tips

  • Plants grown in unglazed clay pots tend to need watering more frequently than plants grown in plastic pots, because the clay is porous.

  • Only use room temperature water. Do not use cold water.

  • Avoid softened water. Let the water sit at least 24 hours to allow the chlorine and fluoride to dissipate.

  • Remember to water your plants when they need it and not according to the calendar.


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