While we are in the Dog Days of Summer, it is a good time
to consider watering in your yard and gardens and how to do so efficiently.
There are some myths on this subject that I would like to discuss. Debunking
these myths can help you water efficiently during hot dry days of summer.
The Top 5 Watering Myths:
During the hottest part of the summer, it’s especially
important to make the most of every drop of water. With so much information
available, it can be challenging to separate fact from fiction. Here are five
common myths about watering:
1. Plants need 1 inch of water per week
Although the “inch-a-week” recommendation is often cited
as a rule of thumb, the truth is that plants vary widely in their water needs.
Young seedlings and new transplants have limited root systems and need a
consistent supply of moisture, so they may need daily watering if the weather
is sunny and hot. Established trees and shrubs, on the other hand, may need supplemental
watering only during extended dry spells because they have root systems that
are more extensive. The amount of water a plant needs depends on a number of
factors, including the type of plant, its stage of growth, type of soil, the weather
and time of year.
The best way to water most plants is by applying enough
to moisten the plant’s entire root system, and then letting the soil dry out
slightly before watering again. Apply water slowly so it’s absorbed by the soil
rather than running off — a soaker hose is ideal. Avoid daily light
sprinklings, which encourage roots to grow near the soil surface where they’re
vulnerable to drying out. Instead of relying on a schedule, water plants when
they need it as indicated by the soil. (Besides, how do you know when you’ve
applied an inch of water with a soaker hose?)
2. Wilting is a sign that it’s time to water
Yes, wilting is a sign that the leaves aren’t getting
enough moisture, but that doesn’t necessarily mean that the soil is dry.
Anything that damages plant roots can cause wilting. Plant roots need a fairly
constant supply of both air and water. Too little water and the roots die from
lack of moisture. Too much water and the spaces between soil particles remain
filled with water, suffocating roots. Both situations reduce a plant’s ability
to deliver enough water to stems and leaves, resulting in wilting. Root
diseases, physical damage (such as disturbing roots while you’re hoeing) and
soil-borne insects can also harm roots to the point that they can’t fully
hydrate the plant. Damage to stems can also cause wilting. Some diseases and
insects (especially borers) prevent water distribution throughout the plant,
causing some or all of it to wilt. The only way to tell if lack of water is
causing wilting is to check the soil moisture.
3. Overhead watering on a sunny day can scorch leaves
There are good reasons to avoid watering your garden on a
sunny afternoon, but causing scorched leaves isn’t one of them. The myth that
water droplets act like tiny magnifying glasses and burn plant leaves has no
basis in fact, and anyone who has watched the sun come out after a summer
shower knows that the water quickly evaporates. Leaf damage can be caused by
all sorts of things: too much or too little soil moisture, fertilizer burn from
improperly diluted synthetic fertilizer, insect or disease problems, and
weather conditions, such as wind or frost, to name a few. Try to avoid watering
on sunny afternoons to minimize the amount of moisture lost to evaporation, but
don’t worry about leaf scorch.
4. Avoid overhead watering with a sprinkler
It’s usually best to apply water directly to the soil
around plants rather than watering with a sprinkler. Less water is lost to
evaporation, especially on hot, sunny days. Foliage stays dry, minimizing
disease problems. However, there are times when an overhead shower is called
for. During dry, windy weather, a fine layer of dust can build up on leaves,
reducing the plants’ ability to photosynthesize efficiently. Some insects,
including aphids and spider mites, can be kept in check by simply hosing them
off plants. Finally, heat-stressed plants that have wilted even though their
roots are moist can benefit from a cooling shower — the effect won’t last long
on a sunny day but it may provide some relief. Overhead watering isn’t the most
efficient from a water conservation standpoint, but there are times when it’s
called for.
5. Drought-tolerant plants don’t need to be watered
Many young echinacea, sedum and black-eyed Susan plants
have perished because these “drought-tolerant” plants didn’t get sufficient
water at planting time and during their first season of growth. When you set
out a new container-grown plant, the roots are confined to the shape of the
pot. The plants need a consistent supply of water during their first growing
season, until their roots grow out into the surrounding soil. Water them as you
would your annual flowers in their first season. During their second and
subsequent growing seasons, drought-tolerant plants may need supplemental water
only during extended dry spells. Note, however, that just because a plant is
drought-tolerant doesn’t mean it doesn’t fare better with a regular supply of
moisture.
