Host an Event Volunteer Join Tickets

Support the plant database you love!

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
Not Yet Rated

Saturday - August 02, 2014

From: New Haven, MO
Region: Midwest
Topic: Problem Plants, Shade Tolerant, Herbs/Forbs, Trees
Title: Magnolia species are allelopathic
Answered by: Nan Hampton

QUESTION:

Have a healthy Southern Magnolia tree around 8 years old. It seems like everything I plant next to it dies.: Variegated Spirea, Stokes Aster, Hydrangeas. Is there something it secretes like the walnut trees do that kills certain plants? Thanks.

ANSWER:

You are absolutely right that magnolias produce chemicals that leech into the soils around it from fallen leaves, twigs and flowers that affect the growth of many other plants.  The chemicals are sesquiterpene lactones.  Here is a link to a previous question sent to Mr. Smarty Plants explaining allelopathy and magnolias.  As well as the allelopathic effects of the magnolia, it is often difficult to find plants that will grown in the dense shade provided by the magnolia canopy.  The SF Guide's article, What Flowers Grow under Magnolia Trees, suggests some flowers that will grow there, but they are not all native plants and if native, are not native to Missouri.   You can find native plants that are recommended for Missouri on our Recommended page.  Using the NARROW YOUR SEARCH option in the sidebar, choose "Herb" from the GENERAL APPEARANCE slot and "Shade" from LIGHT REQUIREMENT to limit the list small plants that grow well in the shade.  Here are a few that might be able to resist the allelopathic effects of the magnolia.  

Asarum canadense (Canadian wild ginger)

Aquilegia canadensis (Eastern red columbine)

Athyrium filix-femina (Common ladyfern)

Lobelia cardinalis (Cardinal flower)

 Sanguinaria canadensis (Bloodroot)

If you do the search above, you can find more plants.

The best way to fight those allelopathic effects are to keep the leaves, twigs, etc., from the magnolia picked up from under the tree.

 

From the Image Gallery


Canadian wild ginger
Asarum canadense

Eastern red columbine
Aquilegia canadensis

Common lady fern
Athyrium filix-femina

Cardinal flower
Lobelia cardinalis

Bloodroot
Sanguinaria canadensis

More Problem Plants Questions

Why is my Texas mountain laurel growing so slowly?
July 22, 2015 - I have a Mountain Laurel, Anacacho Orchid Tree and Desert Willow on the northern side of our yard - all three get full sun most of the day. The Mountain Laurel is closer to the east side. The other...
view the full question and answer

Eliminating silverleaf nightshade from Albuquerque NM
June 07, 2014 - I have silverleaf nightshade in my yard and would like to eradicate it (yeah, I know, good luck!) or at least control it. Do you have any suggestions?
view the full question and answer

Live oak sprouts in Austin
August 01, 2010 - How can I control the hundreds of live oak sprouts our lovely trees are throwing off? We recently landscaped with rain gardens and the related drainage ditches; they are filled with these very happy ...
view the full question and answer

Defense against poison ivy from The Woodlands TX
March 24, 2014 - Hi and thank you in advance for your help. My husband is allergic to Poison Ivy, Oak, Sumac, or something in our yard. We need someone who is very knowledgeable to come and identify any poisonous pla...
view the full question and answer

How Can I Tell an Invasive Thistle from a Native
May 01, 2012 - Mr Smarty Plants, I have some thistles coming up in my yard. I'd like to keep them if they are native, but not if they are invasive or non-native. How can I tell? My yard is a wild area in West Lak...
view the full question and answer

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