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

Monday - March 12, 2012

From: Mandeville, LA
Region: Southeast
Topic: General Botany, Problem Plants, Trees
Title: Black Walnut tree in LA
Answered by: Anne Bossart

QUESTION:

I was just given a black walnut tree and am trying to determine where to place it. Iíve read on your site that ďCertain plants will not grow under Black Walnut trees because of the juglones that the tree puts in the soilĒ Iím considering one of two sites for planting. The understory of the first site will consist of azaleas and an oriental magnolia, and very nearby are gardenias, purple coneflower and American beautyberry. The second site has several Elliotís blueberry bushes, Virginia sweetspire and a bed containing La. iris and Stokeís aster. Also nearby are a cypress, turkís cap, flame azalea and cardinal flowers. We have numerous squirrel and deer, so Iím sure the husks will be spread all over. Will I kill everything in sight by planting this walnut? Is there a list of the types of plants to which the walnut is toxic?

ANSWER:

Although Juglans nigra (Black walnut) is an important native tree that would thrive in your area, it is probably not a good idea to plant it in your garden setting.

You will find a very good article explaining the science of juglone here in an article from the Virginia Cooperative Extension service.  There are also lists of plants that have some tolerance to juglone, but I have heard of (and seen) plants that are supposed to be tolerant that just don't survive.   Much like lists of plants that are deer tolerant, there are actually no guarantees.  You will also notice that the list of plants that are tolerant is much shorter than the list of plants that are susceptible.

Your garden sounds lovely and you don't mention how much property you have, but it would have to be very large before I would recommend including a black walnut tree in it.  You might not notice the effects for a few years as a newly planted tree does not produce all that many leaves and has a limited root zone but keep in mind that this is an adaptation the tree has developed in order to outcompete other plants in its quest to reach it's ultimate size, usually between 50-75 ft, but the champions can reach up to 150 feet.  Besides the issue of alleopathy with juglone, black walnut is useful for its stain.  Even the lime green outside coating of the nut leaves a dark brown (walnut) stain on whatever it comes in contact with: umbrella and patio furniture cushions, patio stones and concrete, painted wood, the list goes on.  A squirrel eating a nut high up in a walnut tree can spread the debris far and wide.  I speak from experience when I tell you that a mature tree can produce a thousand nuts in a good year. Leaves must be raked up quickly in the fall or they will stain your patio as well and if you have a pond (I am not sure about a swimming pool) they will turn the pond water black in a matter of days.

So ... the short answer is don't plant it.  Return it to the gift giver with the explanation that you just don't have enough space or report that it didn't survive the transplanting process (which is a real possibility as they are quite tap rooted as seedlings).

 

From the Image Gallery


Black walnut
Juglans nigra

More Trees Questions

Water requirements for fruit trees in California
January 15, 2013 - Dear Sir; In which of these options (fruit trees) the need for watering in irrigation process is higher than the others: -Olive tree -Nectarines and peaches trees -Hazelnut trees -Pistachios and ...
view the full question and answer

Pruning Bald Cypress in Wylie, TX
January 02, 2010 - I have a 6 year old bald cypress that sustained damage to the upper portion of its trunk a couple of years ago. Since that time it has grown more outward than upward and developed a rounder shape. I...
view the full question and answer

How can I tell the age of a Pecan tree in Rosenberg, TX?
September 03, 2010 - How can I tell the age of a Pecan tree? I live on the Brazos River and have a lot of large Pecan trees but the largest is approx. 11 ft. around.
view the full question and answer

Growing non-native avocado outside from Austin
December 27, 2012 - My son has a very large avocado tree that he rooted from a pit that is currently growing in a large container. However, it has gotten too big to winter inside. Can it be planted in the ground in Aust...
view the full question and answer

Determination of native plants of North Carolina
April 24, 2006 - I am compiling lists of native plants to use in NC, and found that Dirr (Manual of Woody Landscape Plants) lists introduction dates (xxxx) for MANY of the trees you list as natives, e.g., Acer rubrum ...
view the full question and answer

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