Balancing act

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Consider all the variables when watering houseplants

By Greg Summers

“How often should I water?” is perhaps the most frequently asked question by those who enjoy indoor potted plants.
But there is no pat answer to the question. “Water it as much as it needs to grow” isn’t the right reply.
Variables such as plant type, plant age, growth stage, season, location, type and size of pot, soil mix characteristics, weather and placement have to be considered.
According to the Clemson University Cooperative Extension Service, the main cause of death of potted plants is over-watering.
Roots need both water and oxygen and when surrounded by water, the oxygen gets cut off. These roots may rot, mold and smell, eventually killing the whole plant.
Watering requirements for indoor plants run a wide gamut.
Plants with large or thin leaves and those with fine surface roots normally require more frequent watering than succulent plants with fleshy leaves and stems that can store water. Some plants thrive under moist conditions while others grow better when kept drier.
Plants can grow slower after new growth or a heavy flowering and need less watering during these periods and while they are dormant.
Pots are also a major factor. Water evaporates faster from porous clay pots, which means more frequent watering will be required than with nonporous, glazed or plastic pots. A large plant in a small pot needs more water that a small plant in a large pot.
Different soil mixtures are part of the watering equation, too. Heavy, fine-textured potting soils and those with a lot of peat moss hold more water then loose, porous mixtures containing bark, sand and perlite (volcanic glass).
It’s a given that plants in sunny warm locations need to be watered more frequently than plants in cool, low-light environments.
The rule of thumb is to water when necessary by following this method:
– Touch the soil – Stick your finger into the potting soil mix up to the first joint. If it’s dry at your fingertip, it needs water.
– Tap the pot – When potting soil in a clay pot gets dry, it shrinks away from the side of the pot. Rap the sides of the pot with your knuckles. If the sound is dull, the soil is moist. If it sounds hollow, it needs to be watered.
– Estimate the weight – As potting soil dries out, a definite loss in weight can be observed.
– Judge soil color – Potting soil gets lighter in color as it dries out.
Plant dehydration
Indoor potted plants can suffer from dehydration just as quickly as exterior plants. The problem is many plant owners wait too long to fix it. Don’t wait until the stems and leaves begin to wilt. There are obvious signs that must be addressed as soon as they are noticed. Plant enthusiasts should be on the lookout for the following:
– Slow leaf growth – Plants that take longer than normal to grow to  full capacity are an indication of dehydration.
– Leaf loss – Leaves or flowers that prematurely drop off are a sure sign of plant dehydration.
– Translucence – If light can pass through the leaves, the plant may be dehydrated.
– Discoloration – Leaf edges that become brown and dry out while lower plant leaves curl and yellow.