The rapid onset of unhealthy-looking landscape
plants is cause for concern. Many landscape plants in
Illinois are suffering from extremely dry weather.
Symptoms include severe leaf wilt, yellow leaves, early
fall coloring, and leaf scorch (browning along the
margins) on broadleaf plants, and brown, dying turfgrass.
The symptoms are a result of the roots failing
to supply sufficient water to the leaves. This inability
is influenced by the moisture content of the soil and
by the location and condition of the root system.
The drought conditions have significantly reduced
some plant root systems, making them unable to
supply enough water to compensate for the
tremendous amount lost through the leaves.
As would be expected, some plants are
affected more by drought conditions than others.
Especially affected are potentilla, hydrangea, viburnum,
euonymus, and holly shrubs; redbud trees; spruce
and hemlock conifers; and bog plants such as iris
and astilbe. Fortunately, our native prairie species
adapt well to these conditions and, although the top
growth is dying back, this dieback helps build reserves
into the crown for growth next season.
Knowledge of plants' normal growth habits
is important. For example, although many white
pines continue to show signs of stress (see "White
Pine Problem" in issue No. 12 of this newsletter),
these pines naturally drop last year's needles in late
August through mid-October. By contrast, most other
pines and spruces keep several years of needles. If
they begin to drop last year's needles, severe stress
or disease could be present.
To save the landscape plants, water any
stressed plants now to encourage recovery growth and
root revival. Apply enough water to penetrate
deeply within the dripline. Newly installed plants,
especially those in containers, should be watched carefully
and watered properly. Never overwater. To prevent
plants from sending out succulent, frost-susceptible
growth, avoid fertilizing or pruning until plants are
dropping their fall leaves.