En EspaŅol

Q. Who is Mr. Smarty Plants?

A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

Help us grow by giving to the Plant Database Fund or by becoming a member

Did you know you can access the Native Plant Information Network with your web-enabled smartphone?

Share

Ask Mr. Smarty Plants

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants
    
 
See a list of all Smarty Plants questions
Can't find the answer in our existing FAQs, submit a question to Mr. Smarty Plants.
Need help with plant identification, visit the plant identification page.
 
rate this answer
Not Yet Rated

Sunday - June 20, 2010

From: Philadelphia, PA
Region: Mid-Atlantic
Topic: Non-Natives, Diseases and Disorders
Title: Powdery growth in hydrangea in Philadelphia
Answered by: Barbara Medford

QUESTION:

My hydrangea plants have a weird growth on their leaves that looks like white rice. It looks like it would be powdery if brushed, but I don't want to touch it for fear that it some type of mold. Any idea what it could be?

ANSWER:

There is one hydrangea native to Pennsylvania,  Hydrangea arborescens (wild hydrangea), but we're betting you have a hybrid in your garden. Philadelphia, in the southeast corner of Pennsylvania, is in USDA Hardiness Zone 6b to 7. We think you probably have a form of Hydrangea macrophylla, also known as bigleaf, French, garden or florist's hydrangea.  It is hardy to Zone 6, which means it can do well in your area. However, it is a native of Japan, and therefore out of our range of expertise. At the Lady Bird Johnson Wildflower Center we are committed to the growth, protection and propagation of plants native not only to North America but to the area in which that plant is being grown. 

The best source we found for information on hydrangeas was The United States National Arboretum Hydrangea Questions and Answer. From that same site, you should read the part on Are hydrangeas  bothered  by diseases or insects?. Here is an excerpt from that portion that probably applies to your situation:

"For the bigleaf hydrangea, the major disease problem is powdery mildew (see image at right). It is most common on plants growing in shade and under high humidity conditions. Powdery mildew infested leaves are covered with a light gray powdery-looking substance. Purple splotches may also appear. Powdery mildew rarely kills plants, but is unattractive. Powdery mildew may occur on other hydrangea species, but is most severe on bigleaf hydrangea."

To us, mildew doesn't look like rice on a leaf, but it certainly isn't attractive. Another source for information on disease of hydrangeas is this one from the University of Florida Extension Service, Hydrangea macrophylla.   

Native Hydrangeas from our Native Plant Image Gallery:


Hydrangea arborescens

Hydrangea arborescens

Hydrangea arborescens

Hydrangea arborescens

 

 

 

More Diseases and Disorders Questions

Natural lifespan of wild plum trees
May 12, 2008 - We have a small border of Wild Plum Trees in our yard. Every year it seem that one or two of the biggest trees die. Do they have a specific life span? We transplanted the trees/bushes from the panh...
view the full question and answer

Knots on redbuds in Stillwell, OK
April 07, 2011 - My redbud has knots all over the limbs. Its been this way for a few years now. I can not find a way to take care of this problem. I don't even know what is causing this. Can you help me?
view the full question and answer

Recently planted Monterey Oaks doing poorly in Jourdanton, TX.
September 02, 2013 - We planted 2 nice size Monterrey oak trees in April .they were doing good with new growth on them. But now I have been noticing the leaves are turning brown around the edges. We water about once a wee...
view the full question and answer

Orange patches circling cedar branches
May 15, 2010 - We have dry rusty orange patches that circle several of our Cedar branches. There are a few orange blobs on different limbs, but they do not look like the pictures of Cedar Rust (no horns). The foli...
view the full question and answer

Brown rings on grass under live oaks in Austin
June 13, 2013 - There are brown rings in the grass at the dripline on several Live Oak trees in our neighborhood. What causes this? The trees appear healthy.
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | SITEMAP
© 2014 Lady Bird Johnson Wildflower Center