En Español

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?


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

Thursday - May 05, 2011

From: Round Rock, TX
Region: Southwest
Topic: Diseases and Disorders, Watering, Shrubs
Title: Powdery mildew hits Rock Rose in Round Rock Texas
Answered by: Lleslie Uppinghouse


My beautiful Rock Roses have gotten spots of white fuzzy "fur" on their leaves in the past month. This is not something they have ever had before and I'm worried its some kind of disease. Is it something I should worry about and if so is there some way to treat it? I love my Rock Roses they are one of the few plants that survived Austin's two weeks of freezing temperatures this last winter. I dont want to lose them. I bought them from the LBJ Wildflower Center Spring plant sale two years ago. Sigh.


Powdery mildew is almost unavoidable with Pavonia lasiopetala (Rock rose). Many plants with woody stems and fuzzy leaves struggle with this nuisance. Powdery mildew is a common fungal infection. Hot sun helps reduce the chance of mildew forming so if your Rock Rose is not in the full sun you might want to think about moving it. Also it is important to make sure that this plant has good drainage. Although poor drainage isn't the cause of mildew, the combination of soggy roots with mildew can stress out the plant enough to kill it. Pavonia also likes to be cut back every year, keeping it from becoming leggy. Some theorize that if you do this twice a year rather than once, it helps keep the mildew away.

We are suspecting that it is the cloudy days combined with early hot temperatures that is exacerbating the situation. Once mildew develops you may find that it returns again and again, even in the hot sun of summer.

The good news is that powdery mildew can be beat with household ingredients. Use one half tablespoon of baking soda and a couple of drops of dishwashing soap (something natural if you can) mix it up with one half gallon of water in a spray bottle and spray the leaves. This changes the PH on the leaves slightly making it tough for mildew to form and spread. You might have to do this every now and then to keep the mildew away. Other than being susceptible to powdery mildew, Rock Rose is a tough little plant. Well, worth fighting for.


From the Image Gallery

Rock rose
Pavonia lasiopetala

Rock rose
Pavonia lasiopetala

More Watering Questions

Trumpet Vine Dropping Buds
July 25, 2013 - My trumpet vine is dropping its buds before flowering. This happened last year as well. Do you know what is causing this and what I can do to prevent it?
view the full question and answer

Why is my Weeping Fig crying leaves?
July 27, 2009 - I have a weeping fig that I bought Memorial day in Birmingham, Al. It has 8 or 9 trunks growing altogether. It sits on a porch with eastern exposure, only about 2 hours of sun. It has been losing l...
view the full question and answer

Trailing snapdragon hanging basket has flowers that are turning brown.
June 09, 2009 - Trailing snapdragon hanging basket in yellow, flowers are turning brown all over the plant. Why? I water every day as told & fertilized once in 3 weeks. It was so beautiful.
view the full question and answer

Water eroding corner in Austin
October 25, 2011 - I live close to the Wildflower Center. My yard slopes - as do my neighbors' yards to one corner in my yard. The result is constant moisture in one corner. The rest of the yard is caliche, rocks (m...
view the full question and answer

Watering Native Trees in Georgetown, TX
July 19, 2012 - I installed a native/adapted plantscape in early March including several small trees. They were planted in the rocky soil west of I-35 in Georgetown with plenty of added compost and mulch. Other than ...
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.
© 2016 Lady Bird Johnson Wildflower Center