71 (March/April 2004)
Watering, Not a Simple
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