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
2 ratings

Sunday - August 17, 2008

From: McAlester, OK
Region: Southwest
Topic: Non-Natives, Compost and Mulch, Diseases and Disorders, Shrubs
Title: Failure to bloom of non-native Althea in Oklahoma
Answered by: Barbara Medford

QUESTION:

I have 2 Althea bushes that will not bloom. For the past 2 years, they become covered in buds, which eventually yellow, but never open. The buds are fully developed. This year the branches have started to bow down, but the leaves appear healthy. They are about 3-4 years old. They are in full sun till 3-4 pm and are watered twice a week. What do these bushes need?

ANSWER:

The althea is also called Rose of Sharon, scientific name Hibiscus syriacus. It is a mallow, a member of the Malvaceae family, and native to China and India. At the Lady Bird Johnson Wildflower Center, we are focused on the use of plants native to North America and to the area in which they are being grown. So, this plant falls out of our area of expertise. However, we will see if we can find some information for you on the failure of the blooms on your bushes to open.

Among the things we learned about your plant is that the blooms last just one day, they open in the morning, close in the evening and the closed bud remains on the bush for a while until it drops off. They require ample moisture to flower best and avoid leaf drop. This has been such a hot, dry summer that might be a clue to the problem. However, you say they are 3-4 years old. Did the blooms on the plant ever open? Another thing, bud drop can be caused by too much or too little water or over-fertilization.

So, with these pieces of information, but no real answer to your problem, we are going to make some recommendations in the culture of your plants, and see if that helps. These are not an immediate fix, but over time could help. First, blooms are on new wood, so the plant needs regular pruning. It probably is too late in the blooming season for pruning to do any good for this year. But, when the weather cools off, give the bushes a good haircut.

Second, make sure that the blooms are really not opening at all. Is there any possibility that you only have time to go out in your garden in the evening, by which time the blooms have already closed? For now, stop fertilizing. You may have been over-fertilizing with a high nitrogen fertilizer, which will cause lush green leaves but not blooms. Next summer, about 6 weeks before the time that your bushes have tried to bloom in the past, put a fertilizer on them with a higher phosphate content, the middle number on fertilizer designations. This encourages bloom. Read the instructions on the package to determine how much and how often.

Now, let's address the water issue. We don't know what kind of soil you have, but are betting it's some version of an alkaline clay. Which is probably fine for the Hibiscus syriacus, but it can affect the way the plant gets water. About every other day, stick a hose down in the dirt around the roots and let a slow dribble go in until the water shows up on the surface. If the water stays on the surface more than about a half hour, you have poor drainage. Water can collect around the roots and just sit there. If that is the case, water them less but more frequently. This will be trial and error to see how well the drainage is working. If you can, try to work some organic materials, like compost, into the soil around the roots. This will improve the texture of the soil and definitely improve drainage. And mulch them all with a shredded bark mulch. This will not only help hold in the moisture and protect the plant from heat and cold but, as the mulch decomposes, will add more to the organic content of the soil.

This USDA Forest Service website on Hibiscus syriacus goes into more detail on the matters discussed above, and also mentions a possible blight on the blooms caused by a fungus. It doesn't say what should be done about that, but it would probably be better to try some of the other fixes first before you buy an anti-fungal spray. This site also notes that the plants could use some protection from afternoon sun, and you indicate that they are in full sun until 3 to 4 pm. You probably are not interested in moving them just on that account, but there again, the mulch and additional watering should help the bushes do better.

 

More Non-Natives Questions

Invasive nature of non-native Zoysia japonica grass
April 22, 2007 - I have been reading up on Zoysia grass and I am curious about its invasive nature. Is there a good way to keep it from going into my neighbors' yards? I was thinking about using some edging material...
view the full question and answer

Problems with non-native citrus trees from Mesa AZ
January 13, 2014 - We have one valencia orange tree and one naval orange tree in our Mesa, AZ yard. Just noticed some oranges on both trees have a 1/4 inch diameter hole through the skin and the orange fruit and skin a...
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

Cat eating yucca stalks in England
May 07, 2013 - Is it safe for my cat to eat yucca as she is being sick and its hard to stop her
view the full question and answer

Citrus trees for Austin
May 21, 2008 - I am looking for citrus that grows in the Austin,Tx area. Could you offer any suggestions please?
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