Curling leaves on azalea

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Curling leaves on azalea

Post by Patty Wint » Fri, 29 Feb 2008 09:42:40



I live in the San Francisco Bay Area, near the southern end
of the bay. A few days ago, I discovered that the leaves on
one of my Southern Indica azaleas (a variety called 'Southern
Charm') had curled up along their length. Other than the curling,
the plant looks perfectly healthy. The leaves aren't discolored
and show no signs of distress or insects.

Here's a closeup of one cluster of curled leaves:
http://www.wintertime.com/OH/Azalea/azalea-leaves.jpg

A wider shot showing the foliage area of the plant (it's
a standard/topiary form):
http://www.wintertime.com/OH/Azalea/azalea-body.jpg
(Normally, the branches would not be visible; they'd be
hidden behind the fully opened leaves, as with the low-
growing azaleas in the next photo.)

And a photo of the full tree (note the happy bush-form
Southern Indicas below it):
http://www.wintertime.com/OH/Azalea/azalea-full.jpg

I've been reading back postings on this group and the information
on some websites, and the two most common causes of such curl
seem to be cold, windy weather, and fungi. Although we did have
some high winds several days ago, they were accompanied by rain
and took place in 40-50-degree weather, so it seems unlikely
that the plant is protecting itself from cold, dry conditions.

That leaves me wondering about a fungus. But wouldn't that
cause more damage than just curling?

I put some ground-up oak leaves around the plant a couple of
weeks ago, along with some coir mulch (Mulch Block). I kept
the mulch a few inches away from the trunk of the azalea
(it's a standard/topiary form), but I treated the oak leaves
as a soil amendment and let them get quite close to the trunk.
Was that a mistake? I did the same thing a few months ago with
no problems, but maybe it wasn't a good idea in rainy weather?
I've now pushed everything out several inches, although if
it did allow a fungus to take hold, I realize that moving
the leaves and mulch isn't enough to solve the problem.

As you saw if you looked at the wide-angle photo, I have other
Southern Indicas in the same landscaping bed, and they're all
looking great. They were put in two years ago; the Southern
Charm went in last spring. So the others are better established,
if that matters.

Should I put some fungicide on the roots, or could something
else be causing the leaf curl?

Thanks!
Patty

 
 
 

Curling leaves on azalea

Post by Stephen Hennin » Mon, 10 Mar 2008 02:28:22


Hi Patty,

The good news is that your azalea looks very healthy.


Quote:
> I live in the San Francisco Bay Area, near the southern end
> of the bay. A few days ago, I discovered that the leaves on
> one of my Southern Indica azaleas (a variety called 'Southern
> Charm') had curled up along their length. Other than the curling,
> the plant looks perfectly healthy. The leaves aren't discolored
> and show no signs of distress or insects.

> Here's a closeup of one cluster of curled leaves:
> http://www.wintertime.com/OH/Azalea/azalea-leaves.jpg

There are a number of natural responses that will cause leaf curl.  The
most common is cold weather but that usually only occurs in near
freezing weather. The other is drought.  They naturally curl to conserve
moisture.  However, they curl the opposite direction for these stresses.  
If you have had a lot of rain, then you may be getting the reverse
response.  I don't remember ever seeing it before, but it is very
possible.

The stomata are pores on the underside of the leaves that release
moisture.  When the plant has desiccation stress from cold weather or
root damage, then the leaves curl the other direction to protect the
underside of the leaves.  This same physiological response could be
causing the leaves to curl the way they are to accelerate the loss of
moisture, indicating your plant is in a location that is too wet.

Quote:
> I've been reading back postings on this group and the information
> on some websites, and the two most common causes of such curl
> seem to be cold, windy weather, and fungi. Although we did have
> some high winds several days ago, they were accompanied by rain
> and took place in 40-50-degree weather, so it seems unlikely
> that the plant is protecting itself from cold, dry conditions.

> That leaves me wondering about a fungus. But wouldn't that
> cause more damage than just curling?

Your leaves show absolutely no damage, so it doesn't look like fungi.
Also, the curling is in the wrong direction for fungi, or other
desiccation problems.

Quote:
> I put some ground-up oak leaves around the plant a couple of
> weeks ago, along with some coir mulch (Mulch Block). I kept
> the mulch a few inches away from the trunk of the azalea
> (it's a standard/topiary form), but I treated the oak leaves
> as a soil amendment and let them get quite close to the trunk.
> Was that a mistake? I did the same thing a few months ago with
> no problems, but maybe it wasn't a good idea in rainy weather?
> I've now pushed everything out several inches, although if
> it did allow a fungus to take hold, I realize that moving
> the leaves and mulch isn't enough to solve the problem.

> As you saw if you looked at the wide-angle photo, I have other
> Southern Indicas in the same landscaping bed, and they're all
> looking great. They were put in two years ago; the Southern
> Charm went in last spring. So the others are better established,
> if that matters.

I don't see any connection.  I think it is too much moisture.

Quote:
> Should I put some fungicide on the roots, or could something
> else be causing the leaf curl?

No.

Azaleas need three things, acidic soil, drainage and drainage.  I am
guessing this plant may have a drainage problem.  If you have poor
drainage and get warm weather, then you will get fungi problems.  You
need to address the drainage issue quickly while the plant is still
healthy.  The easiest way is with a raised bed unless you can improve
drainage in the vicinity of the plant.
--

Visit my Rhododendron and Azalea web pages at:
       http://rhodyman.net/rahome.html
Also visit the Rhododendron and Azalea Bookstore at:
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Cheers, Steve Henning in Reading, PA USA  Zone 6