Home > Begonian > Volume 71 (March/April 2004)

Watering, Not a Simple Chore
by Morris Mueller

Watering is not a glamorous topic to write or read about. Yet this topic is most essential to growing and upon consideration is not as simple as dumping water on a plant. Without thinking consciously about it, I realized how complex watering really is for me. There are a lot of considerations that go into watering each and every plant.

Is it spring, summer, fall or winter? The season has much to do with how often to water. And the season is influenced by day-length, temperature, humidity and wind. The longer the day the more the plant transpires water. This is true also for higher temperatures and windy conditions. The more sunlight the plant receives outside the more frequently it needs water. The lower the humidity and again more water. This is true also for higher temperatures and windy conditions. The lower the humidity and again more water.

The potting media and pot type also determine watering. Well draining soils, which begonias like need more frequent watering than do heavier general use potting mixes. Clay, wood, and other types of porous pots need more frequent watering than do plants in plastic pots. Pot size also helps to determine when to water; the larger the pot most often the less water it will need, but there are other considerations addressed later in this article.

Where the plant is placed also must be considered. Inside, outside-location has a lot to do with watering. Inside on a light cart plants on the lowest level need less water than those on the upper shelves. Inside plants need less water usually than those outside in all seasons except winter. Enclosed terrarium plants, of course, need less water than plants grown in pots or the ground. Also plants grouped close together need less frequent watering than those isolated, because groups of plants increase the humidity around them. Some more unusual considerations also go into how, when, and how much to water a given plant. Plants with less foliage require less water than those with many leaves. A plant that is not too healthy requires less water than one that is growing vigorously. And certainly one that is either semidormant (tuberous, semi-tuberous) or completely so needs only minimal water. A plant with thin leaves will require more water than one with thicker leaves although this may not always be true. The type of plant and where it originated (or its parents if a hybrid) determines how it is watered. For example, B. peltata has low water needswhile Southeast Asian species have high water needs. Plants that are pot-bound will dry out more quickly than those that still have room to grow actively, thus potbound plants need more frequent watering. One way to help determine the potbound (and any needing water) is if a small bit of water sits on top of the soil and doesn't soak in immediately. That pot needs more water than one where the water soaks in immediately.

Color of soil can also help determine water needs: dark means soil is moist, light means it is dry or drier. A heavy pot needs less water than a lighter pot of the same size. The best test of all is a finger pushed down into the soil which will indicate if a pot needs water or not. Obviously a plant that appears wilted needs water; however there are two other ways to tell if water is needed. Some plants have foliage that turns glossy showing they need water. Also with some plants when you touch the leaves they are soft and not rigid , again indicating the need for water.

One last point, if a particular plant dries out between waterings, put it in a saucer only slighter larger than the pot. The water the saucer retains will most likely not rot the roots and will give you an extra day or two between waterings.

Maybe there is nothing in this article you didn't already know, but have you ever consciously tried to put it all together?