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
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

a source for fruitless olive (non-native) trees
June 29, 2012 - I was given a "mexican olive" several years ago which is doing very well. This one is non-fruiting and I would like to have another that is non-fruiting but cannot find one. Cordia boissieri see...
view the full question and answer

Failure to thrive of non-native Japanese maple
May 03, 2010 - My 10 year old Japanese red maple leaves suddenly started to curl up and die at the end of summer last year. Only about a quarter of the tree leaved out this spring, branches are dead. Can I plant ano...
view the full question and answer

poor blooming on (non-native) plumbago
June 14, 2011 - I recently purchased several blue Plumbago plants that were covered in blooms. We planted them in our front beds that receive about 5 hours of morning sun then afternoon shade. I have watered them eve...
view the full question and answer

Newly planted Burford Holly doing poorly in Austin, TX.
July 25, 2011 - About a month ago I bought dwarf burford holly. Now they have slowly started getting brown leaves that eventually fall off. Some of the plants have white spots on the ends. I usually check my plant...
view the full question and answer

Need help with Wheeler's Dwarf Pittosporum
September 02, 2015 - We have about five Dwarf Wheeler Pittosporum plants. All of them are mature and were doing well. I was on vacation for a week or so and when I came back I saw of each of them is plant 90% dead. The d...
view the full question and answer

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