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

Red maple a casualty of Hurricane Ike in Houston
November 21, 2009 - We have a 3 year old Drummond Red Maple, between the sidewalk and the street in front of our house, that fell during Hurricane Ike. We replanted it. I recently noticed that the bark is severely cracke...
view the full question and answer

Mutation in bluebonnets from Elgin TX
April 16, 2013 - What causes bluebonnets to mutate..grow as if three or four are combined into one flower on one very flat, wide stem. I have these in my yard; they are beautiful! I have taken several pictures.
view the full question and answer

Something eating holes in Texas Betony from Austin
June 06, 2012 - What pest is eating holes in the leaves of my Texas Betonys? They look healthy but almost all leaves have various sizes of round holes in them. What is the best cure for this? Thanks
view the full question and answer

Pecan tree dropping limbs in Grand Prairie, TX.
September 04, 2012 - Our 15 year old pecan tree is losing it's limbs. The tree and its leaves look healthy with no signs of bugs or mites, but all the limbs are drooping and breaking off. The tree did have a bumper crop ...
view the full question and answer

Problems with Green Cloud cenizo in Tucson, AZ
June 15, 2009 - I have a large number of Green Cloud Texas Rangers on my property. I water all very consistently, once a week and most of these are around 5-6 ft tall and 15 years or more old. We've only had a few i...
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 | STAFF
© 2015 Lady Bird Johnson Wildflower Center