En Espa—ol

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

Tuesday - June 19, 2007

From: Pflugerville, TX
Region: Southwest
Topic: Compost and Mulch, Propagation, Seeds and Seeding
Title: Allelopathc qualities in sunflowers
Answered by: Barbara Medford

QUESTION:

I have a sunflower patch in the corner of my backyard (Maximilians, common sunflower, and silverleaf sunflower)and would like to use the spent stalks (sans the seedheads) as mulch in the fall. However, I've read that sunflower is allelopathic to other plants. Is this only while they are actively growing, or would mulching with them inhibit growth of other plants? Are there certain plants that would or would not tolerate a sunflower-based mulch?

ANSWER:

Sunflower seed may be allelopathic in some situations, and certainly sunflowers will freely sprout everywhere, often with the help of birds, who are no doubt delighted that you are contributing to their diet. You should never use the seeds as mulch without first composting them for at least a month. The heat of the compost will help to leach out the toxins in the sunflower seeds. If you are going to mulch with stalks and leaves, removing the flowers and seeds, you would probably not need to compost first. Sunflowers grow so fast and so tall that they often will shade out weeds at their feet and/or kill them with the seed toxins. Most of the information I found on sunflower seeds damaging plants involved plants under bird feeders. The discarded seeds and hulls can build up to quite a depth if you are a devoted feeder of wildlife, and will certainly smother just about anything that tries to come up. In your case, you might just let the birds (finches are especially fond of sunflower seeds) enjoy the seeds still on the plants, then clean up the leftover debris and discard it NOT as mulch, at least until it has been composted.

 

From the Image Gallery


Maximilian sunflower
Helianthus maximiliani

Maximilian sunflower
Helianthus maximiliani

More Seeds and Seeding Questions

Dill-like plant in veggie garden in California
September 28, 2011 - I have a plant that appeared in my veggie garden. Looks like dill in spring when green, but the leaves smell more like turpentine! Now, 4-5 foot tall, brown, it produces lots of small, oval - not cr...
view the full question and answer

Propagation of Chandler's craglily from San Marcos TX
December 16, 2012 - Can you please advise me on collecting and propagating seed from Chandlerís craglily -Echeandia chandleri. I have 2 plants that came from the wildflower center. They never seem to multiply, but they d...
view the full question and answer

Getting milkweed seeds into seed mixes from Milwaukee WI
February 07, 2014 - My husband and I are concerned about the Monarch butterfly migration and have started an effort to get milkweed planted along some bike trails here in Wisconsin. This made me think of Ladybird Johnso...
view the full question and answer

Different colors of Argemone spp. from McAllen TX
March 16, 2014 - I took pictures of at least 5 colors of pricklepoppy today. Is this common to have so many colors in one area? How do I harvest the seedpods and when is the best time to do so?
view the full question and answer

Failure of flameleaf sumacs to produce fruit
January 09, 2013 - Our two flame leaf sumacs produce none to little fruit. Both are about 4 years old, quite large, healthy looking; flowering this year was very good, but no fruit. What keeps them from producing fruit?
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