Rent Shop Volunteer Join

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

Please forgive us, but Mr. Smarty Plants has been overwhelmed by a flood of mail and must take a break for awhile to catch up. We hope to be accepting new questions again soon. Thank you!

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 Non-Natives Questions

Response to previous answer on non-native cacti
March 15, 2008 - Hi Mr. SmartyPlants, Santa Barbara here, again. Thanks for all your effort, especially as it falls outside of the Center's general expertise. That Cacti.com is amazing and I found the answer in the...
view the full question and answer

Mosquito problem from Mesa AZ
April 07, 2014 - We have a mosquito problem in our backyard, I think they're grass Mosquitos. I wanted to get lemongrass for a deterrent but both nurseries were out so I opted for rosemary. They're ALL OVER the rose...
view the full question and answer

Problem with non-native Chocolate Silk Tree, Albizia julibrissin
June 09, 2009 - How do we get our Chocolate Silk Tree that once had redish brown leaves from now green to the original color? Thank You.
view the full question and answer

Difficulty with Clay Soil from Palm Bay, FL
August 22, 2012 - I had a very nice little native shady area behind my house for over 40 years, but now it has been cleared except for a 100 foot tall live oak in the center of this raised mound (50' x 80'). I've be...
view the full question and answer

Care of non-native house plant, Pachira aquatica
October 14, 2007 - Mr. Smarty Plants, I have just bought a miniature money tree. I would like to plant it on a metal like decorative pot. What advice would you give me how to prevent the plant from getting any metal re...
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.