Although you would think we get enough
rain in Northern Virginia to keep any sort of plant happy, in fact,
sometimes you will have to supplement your plants’ water in order
to keep them healthy.
There are several situations where
rainwater might not be enough. New sod, for instance, needs to be
kept consistently moist until it is well established -- it cannot
wait three days for the next good downpour.
Trees sometimes do not fare well,
especially in dry years or in urban settings. A mature oak can absorb
100 gallons of water per day, and if the groundwater is
insufficient, it will wilt. This powerful thirst is not unique to
oaks -- all trees need water. The big ones need more than the little
ones, and the young ones will sometimes need supplementation because
their roots are not yet deep enough to get at the ground water.
Runoff from poor soils can also be a
factor. Two inches of rain does no good if it doesn’t soak into the
ground. Sometimes the ground is too compacted for it to absorb, or
the terrain is steep and the water washes away before it has a chance
to soak in.
As you can see, there are many
situations in which is necessary to water. Watering by hand is by far
the best option, because this enables you to put exactly as much
water is needed, right where it will do the most good. A watering
wand is the best tool for the job here.
Since it’s not possible sometimes to
water by hand, soaker hoses or sprinklers can be used instead.
The rule of thumb is “water deeply
and infrequently.” Except for new sod, this works for nearly all
plants. The only thing that changes is the definition of “deeply”
and “infrequently.” The idea is that you want to thoroughly
saturate the root ball until it resembles a dripping sponge, and then
allow it to absorb that water over a period of time, and not water
again until it is barely damp.
So for your roses this might be every
three days, and for your weeping cherry this might be every week or
ten days.
Watering like this will encourage the
roots to grow down deeply, rather than shallowly, because you will
have “taught” the plant that the water is more plentiful the
deeper it goes rather than close to the surface.
And of course, don’t forget to add a
thick layer of mulch around your plants. This will hold rainwater
long enough for it to soak in, and reduce evaporation so you can
water less often. Good gardening!