Azalea Care
Brian Jervis: Ask a
Master Gardener
Sunday, July 22, 2018
Q: I have azalea bushes
that are so beautiful in the spring but then develop problems over the summer.
Should I just live with these issues or is there something I can do to help
make them look better through the summer? Michelle T., Broken Arrow
However, the dream of
such garden beauty sometimes comes into question when spots and holes appear in
leaves, the foliage turns yellow or flower buds remain closed. While azaleas
can withstand many of the insect and disease problems that plague other plants,
there are still a few problems that can occur.
First of all, plant in
the right location (east facing with good morning sun is the best), with good
drainage and air circulation between plants to help prevent problems. However,
when that is not sufficient, here are a few of the most common offenders:
Aphids: These may appear on the stems of any
plant when the weather is humid and plants are too close together without
enough air circulation. Treat aphids with a hard spray of water from the hose.
Lace bugs/spider
mites: Azalea lace bugs
make up about 90 percent of all azalea pest problems. They feed on leaves,
creating speckled areas on the leaf surface. Spider mites cause white stippling
on leaves first, but then the area turns a rust or gray color. Both can be
treated with insecticidal soap, horticultural oils or a systemic insecticide
that includes the ingredient imidacloprid. Use it as a soil drench once yearly
after blooming to avoid harming bees.
Fungus-related issues: Leaf galls, rust, petal blight and leaf
spot are caused by fungus. Petal blight appears as tiny white spots on flowers.
Leaf spot manifests as brown blotches that grow in size. Treat with a
fungicide.
Root rot/water mold: Azaleas may also be impacted by another
fungus that causes root rot, sometimes called water mold. Azaleas that stand in
water during warm weather are particularly susceptible. This occurs mostly when
azaleas are planted as a foundation plant near a down spout. This fungus
spreads fast, so watch for yellowing leaves and wilting plants.
Iron Chlorosis: Azaleas prefer acidic soils. If not
planted in such, leaves will turn yellow. With this condition, a soil test is
always in order, which can confirm the actual soil pH.
To assist in
preventing these issues, azaleas should be mulched with several inches of pine
bark, and some of the bark should be incorporated directly into the planting
soil to help add oxygen and ensure thorough drainage.
Protect your valuable
and beloved plants with regular attention, looking carefully for potential
problems along stems and branches, as well as under leaves. And, when it comes
to chemicals, more is never better. Small infections and infestations may go
unnoticed, only to grow into larger issues later. Therefore, it is best to
examine your azaleas every time you water.
For more information
and assistance with azaleas, drop by the Tulsa County Extension Office or
call the Master Gardener hotline at 918-746-3701 to speak with a
Tulsa Master Gardener.
Garden tips
·
When watering your lawn,
ornamentals or vegetables, always do so in the morning, if possible. If watered
in the evening, plants will go into the night still moist. Most disease-causing
organisms need moisture and, because they grow best at night, leaving leaves
wet in the evening will promote many plant diseases.
·
Bulb onions are ready
to harvest when the tops fall over. They should be removed and allowed to dry
in a well-ventilated, shaded area. After the tops are completely dry, they may
be stored in a cool, dry area.
·
Tomato production
stops in the heat of the summer. Most tomato pollen becomes infertile and
blossoms drop off when the night temperatures are above 70 degrees and daytime temperatures are above 92 degrees for a few
days. Tall, spindly tomato plants with scarce fruit are usually due to either
too much nitrogen fertilizer or too much shade. If this occurs, cut them back
by ⅓. New growth and fertile blossoms will develop when it cools in the fall.
