I planted
a new azalea and it died. What did I do wrong?
It may have simply dried out. If you plant azaleas in late spring, it is
very important to give them some extra water while they are growing new
roots. Never let the soil completely dry out it's best to keep the soil
evenly moist. Too much water or poorly drained soil might be another explanation
of sudden azalea death. Azaleas have very fine, fibrous roots that are
easily damaged by waterlogging, even for short periods of time. Before
you plant your azalea, dig a hole and fill it with water. If the water
has not drained out of the hole within one hour, the soil is poorly drained
and you must correct the drainage problem before planting. Install a perforated
pipe or drain tile in the garden, making sure that the outlet is lower
than the bottom of the planting hole, or build raised beds.
Can you tell me how to plant
an azalea?
Plant your azalea in early spring or early fall. If your soil is loose,
well drained, and has lots of organic matter, planting will be easy. If
drainage is poor, you'll need to correct the drainage problem or plant
in raised beds. You can work in some well-rotted leaf mold or compost if
the soil is short of organic matter. Don't worry about preparing the soil
deeply since azalea roots are shallow and most are found in the top foot
of soil. Instead, loosen the soil in a broad area around the planting site.
If a soil test reveals that your soil is strongly alkaline, work in enough
iron sulfate or ammonium sulfate to drop the pH to 4.5 to 5.5; your state's
soil testing lab can give you guidance on how much of these materials are
needed to acidify your soil. Water the pot thoroughly before planting and
tease the soil away from the roots on the outside of the pot. Don't worry
about injuring the roots it's more important to remove a significant amount
of the potting soil than it is to keep every root intact. Plant the azalea
slightly higher than the surrounding soil since it will probably settle
after planting. Finally, water the whole area thoroughly and apply a thin
layer of shredded leaves, pine needles, or pine bark to keep the soil cool
and moist. Water your newly planted azalea weekly if the weather is dry,
at least for the first year.
An old,
established azalea died in my garden. What might have caused its death?
There are several possibilities. Voles, also known as meadow mice, may
have chewed on the bark and roots near the crown of the plant. Sometimes
they chew all the way around the trunk and kill the inner bark, resulting
in death of the whole plant. Keep mulch away from the trunk to discourage
voles. The bark may also split when there are wide fluctuations in temperature
in the winter. Azaleas may begin to come out of dormancy if late winter
weather is warm; if a cold snap follows, bark injury is likely, especially
in sunny, exposed sites. Prolonged drought weakens plants and often results
in the appearance of fungal cankers on the branches of older azaleas. Look
for branches that wilt in hot, dry weather in late summer and be sure to
water azaleas if drought drags on more than a few weeks. Prune out the
affected branches to stop the spread of fungal canker diseases.
What should I use to
mulch my azaleas? Should I amend the soil at the time of planting?
You can mulch azaleas with shredded leaves, leaf mold, pine needles, or
pine bark mulch. Don't use shredded hardwood mulch since it often drives
the pH upward. Pine bark is especially useful since it can lower the pH
where it is too high, but it is best used on relatively flat ground since
it's light in weight and tends to float away in heavy rain.
You only need to amend the soil if it is devoid of organic matter or
if the pH is too high. Have a soil test done by your local extension service
to determine if something needs to be added. A light amount of well-decayed
organic matter dug into the top layer of soil is helpful for retaining
moisture and preventing compaction.
How and when should
I prune my azaleas?
Prune azaleas just after they have finished flowering. Remove individual
branches back to the spot where they join a larger branch. New flower buds
for next spring's bloom are set by midsummer, and any pruning after mid-June
could result in diminished flower production next year. Avoid shearing
azaleas since it results in a proliferation of unhealthy, twiggy growth.
Check azaleas for wilting or dead branches in late summer that may be the
result of fungal cankers. These branches should be pruned back to clean
white wood that is not infected while the weather is dry to prevent the
spread of diseases. Old azaleas that have grown too large for their space
in your garden can be brought down in size by cutting the large branches
back severely. New growth will spring from the stubs that are left.
What is
the difference between a rhododendron and an azalea?
Taxonomically, Rhododendron is the correct genus name for all azaleas
and rhododendrons. Azaleas generally have smaller flowers, bloom a bit
earlier, and have much smaller leaves that may be deciduous or partly so.
Rhododendrons usually have larger flowers, bloom later, and have large
leaves that persist during the winter.
When should I fertilize
my azaleas? What fertilizer should I use?
Established azaleas often do well with no fertilizer at all. Nutrients
are slowly released by any organic mulch that you use, so rely on this
as the primary source of nutrients. Excess nutrients may promote larger
than normal populations of azalea pests like lace bugs and azalea whiteflies.
If your azalea foliage loses its deep green color, test your soil to make
sure that the pH is not too high.
If a soil test reveals that nutrients are extremely low, fertilize azaleas
in the spring or fall. Use a granular, slow-release fertilizer that is
acid-forming and apply a very light scattering around the edge of the root
zone of the plant. Never apply more than a few tablespoons at any one time;
excess fertilizer can easily burn the delicate roots of azaleas since they
are so close to the soil surface. Scorched leaf margins often result from
overfertilization.
Why isn't my azalea blooming?
Too much nitrogen in early summer may encourage vegetative growth at the
expense of flower bud formation, so limit fertilizer applications to the
fall or spring or skip the fertilizer all together. Although azaleas are
well adapted to partial shade, deep shade produces spindly, weak growth
and few flower buds. Azaleas usually won't flower well if planted under
trees with dense foliage, such as maples, beeches, and pines. Plant in
the diffused light under widely spaced, high-crowned trees like oaks and
tulip poplars. Deer and rabbits may eat many of the flower buds as they
browse in the winter, particularly if the weather is harsh and other food
is scarce. Flower buds can also be damaged by cold, dry winds, particularly
when warm winter weather is followed by a period of bitter cold.
My azaleas
always turn yellow or purple in winter. What's wrong?
Nothing is wrong. Like all evergreen plants, azaleas periodically lose
some of their foliage, and the leaves may turn yellow, red, or purple before
they fall. Often the only leaves that remain are those that surround the
flower buds at the tips of the branches. This characteristic is linked
to the genetics of the parents used to breed garden azaleas. The degree
of leaf coloration or loss is a function of parentage and not the severity
of the winter. In unusually cold winters, certain azaleas may lose more
leaves than they would in mild winters.
My azalea
foliage looks white, and there are black bugs underneath the leaves. How
can I get rid of them?
You
undoubtedly have a problem with the azalea lace bug. This insect hatches
early in spring as the new foliage begins to mature and its numbers may
build to damaging levels with successive generations. Lace bugs reach their
peak in late summer and do their worst in sunny, exposed sites. Spiders
are important predators of lace bugs and since they shy away from sunny,
hot places, plant your azaleas where there is some shade. Insecticidal
soap, horticultural oil, or a systemic insecticide may spare your azaleas
the damage if applied in spring when the first hatchlings are noticed.
All the
leaves on my azaleas are notched, and they are growing poorly. I don't
see any insect or pest causing this damage. What's going on?
The damage you describe is that of the black vine weevil, a small nocturnal
weevil that, in its larval stage, feeds on azalea and rhododendron roots.
As the new leaves expand in the spring, adult weevils emerge from the soil
and make nightly visits to the leaves to feed, chomping sections out of
the margins of the new leaves. Black vine weevils can't fly, so they don't
spread rapidly. They spread most commonly in container plants and a few
larvae in a single pot may start an infestation that may damage dozens
of plants in your garden. Black vine weevils are very hard to get rid of,
so quarantine new plants for several months before planting to make sure
they are not infested. A pesticide containing imidacloprid may help control
them.
My azalea
flowers never last more than a few days in spring. Then they cling to the
plants and turn brown. Why?
Wet weather in spring often results in serious damage from a fungus disease
called azalea petal blight. Apply a fungicide labeled for petal blight
just as the petals begin to show color. If treated at the right time, and
if temperatures are not too hot, the blossoms may last as long as three
weeks and will drop off the plant instead of turning brown and mushy.
Can I transplant a large
azalea? If so, how should I do this?
Azaleas have very shallow root systems, so even large azaleas may be successfully
transplanted. It is important to dig a wide root ball. Don't worry about
digging deep into the soil since most azalea roots are near the surface.
The best time to do this is early spring or early fall when the weather
is cool. Begin by preparing the new planting site. Then dig the azalea,
preserving a root ball as wide as can be safely moved. You can lift it
onto a tarp and then use the tarp to drag the plant to its new location
rather than picking it up. Be sure not to plant the azalea too deeply and
water it thoroughly after transplanting.
I'd like
to see the azaleas in full bloom. When should I come to the U.S. National
Arboretum?
Peak bloom can vary by two weeks or more, depending on the weather, but
usually takes place around the end of April. The earliest peak bloom date
reported in the last decade was April 15; the latest was May 4. Keep in
mind that many azaleas are in bloom long after the peak and others might
bloom early there are usually some azaleas in bloom from early in April
until well into June. Before you come, check the Azalea
Blossom Watch page to see what is in bloom.
Where can I find
more information about azaleas?
Check out the Azalea Society of America web page at www.azaleas.org.
Another good source for information about azaleas can be found at www.theazaleaworks.com.
A broader source of information that includes rhododendrons as well as
azaleas can be found at the American Rhododendron Society web site at www.rhododendron.org
or at the Rhododendron Species Foundation web site at www.rhodygarden.org/index.html.
If you are looking for a particular azalea variety, check the Plant
Sources Page for tips on locating a source.
Plant your azalea in early spring or early fall. If your soil is loose,
well drained, and has lots of organic matter, planting will be easy. If
drainage is poor, you'll need to correct the drainage problem or plant
in raised beds. You can work in some well-rotted leaf mold or compost if
the soil is short of organic matter. Don't worry about preparing the soil
deeply since azalea roots are shallow and most are found in the top foot
of soil. Instead, loosen the soil in a broad area around the planting site.
If a soil test reveals that your soil is strongly alkaline, work in enough
iron sulfate or ammonium sulfate to drop the pH to 4.5 to 5.5; your state's
soil testing lab can give you guidance on how much of these materials are
needed to acidify your soil. Water the pot thoroughly before planting and
tease the soil away from the roots on the outside of the pot. Don't worry
about injuring the roots it's more important to remove a significant amount
of the potting soil than it is to keep every root intact. Plant the azalea
slightly higher than the surrounding soil since it will probably settle
after planting. Finally, water the whole area thoroughly and apply a thin
layer of shredded leaves, pine needles, or pine bark to keep the soil cool
and moist. Water your newly planted azalea weekly if the weather is dry,
at least for the first year.
Too much nitrogen in early summer may encourage vegetative growth at the
expense of flower bud formation, so limit fertilizer applications to the
fall or spring or skip the fertilizer all together. Although azaleas are
well adapted to partial shade, deep shade produces spindly, weak growth
and few flower buds. Azaleas usually won't flower well if planted under
trees with dense foliage, such as maples, beeches, and pines. Plant in
the diffused light under widely spaced, high-crowned trees like oaks and
tulip poplars. Deer and rabbits may eat many of the flower buds as they
browse in the winter, particularly if the weather is harsh and other food
is scarce. Flower buds can also be damaged by cold, dry winds, particularly
when warm winter weather is followed by a period of bitter cold.
You
undoubtedly have a problem with the azalea lace bug. This insect hatches
early in spring as the new foliage begins to mature and its numbers may
build to damaging levels with successive generations. Lace bugs reach their
peak in late summer and do their worst in sunny, exposed sites. Spiders
are important predators of lace bugs and since they shy away from sunny,
hot places, plant your azaleas where there is some shade. Insecticidal
soap, horticultural oil, or a systemic insecticide may spare your azaleas
the damage if applied in spring when the first hatchlings are noticed.
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