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

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

QUESTION:

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.

ANSWER:

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 Shrubs Questions

Needs Help with Peonies
January 14, 2011 - With the clay soil in North Texas (Frisco) which variety of peony would thrive and become a reliable bloomer? I do work on amending the soil with expanded shell and compost, but ultimately, we still h...
view the full question and answer

Are beautyberry bushes toxic to horses?
October 12, 2011 - Are beautyberry bushes toxic to horses?
view the full question and answer

Can Calycanthus floridus survive in South Dakota?
March 06, 2009 - Calycanthus in South Dakota? I've recently purchased some seeds for a calycanthus plant (floridus I think). I'm going to start them indoors but am wondering if this can survive a South Dakota winter...
view the full question and answer

Esperanza failing to bud out in Georgetown TX
March 28, 2010 - I planted esperanza shrubs last summer and they did well. I did not prune them back in the winter. They are not showing any signs of life (No greenery) Will the plants start to form leaves and flow...
view the full question and answer

Small shrub for Point Richmond CA
August 19, 2013 - I'm looking for a plant that grows 4-6 feet tall, but not too wide (more than 2-3 feet). I'd like it to be flowering (any color but white and preferably not red). It will be located between a salvi...
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