En Español

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
1 rating

Tuesday - November 15, 2011

From: Austin, TX
Region: Southwest
Topic: Propagation, Seeds and Seeding, Trees
Title: Mexican Sycamore trees grown from seed
Answered by: Jimmy Mills

QUESTION:

If someone is selling an alleged Mexican Sycamore grown from a seed harvested from a mature tree growing in Austin, is it likely to be a TRUE Mexican Sycamore -- or has it most likely been pollinated by an AMERICAN Sycamore, such that the resulting hybrid has an unpredictable mix of M. Sycamore and A. Sycamore traits? I have wondered because when almost every such tree I've seen for sale in Austin has leaf undersides which usually seem to lack the silvery sheen [or at least whitish cast] and/or the fuzzy underside that I've always assumed was the mark of a TRUE Mexican sycamore. How can I know if I'm getting "the real deal"? Are these trees simply hybrids at best -- and not true Mexican Sycamores?

ANSWER:

You seem a little skeptical which is a good thing.

Lets learn a little more about Sycamores. The American Sycamore is Platanus occidentalis (American sycamore), and the Mexican Sycamore is Platanus mexicana.
P. occidentalis is native to the U.S., but P.mexicana is native to Mexico and therefore is not found in our NPIN Database. The Mexican sycamore has become popular in the last ten years as an introduced ornamental.

Sycamore trees are monoecious, having both pistillate (female) and staminate (male ) flowers on the same plant. However, it is doubtful that they are self-fertile,  ie. pollen from staminate flowers can not pollinate pistillate flowers on the same tree.  The trees are also wind pollinated. Since P. occidentalis and P. mexicana are closely related, it is not out of the question that they are able to cross pollinate and produce viable hybrids. So there is no way of knowing if the seed from which the tree being sold grew was the result of pollination from P. mexicana  or  from P. occidentalis. The odds of the tree being a hybrid seems pretty high unless the seed parent was growing in a grove of P. mexicana.

How can you tell the difference? One character that is easy to see is the the shape of the leaves. The link to austintreeexperts.com  says that P. occidentalis leaves are broader at the base, and will generally have an extra lobe that is lacking in P.mexicana. There are two photos on the link that show this distinction.

These two links from the Texas Forest Service have illustrations that also demonstrate this feature:

    Platanus occidentalis

    Platanus mexicana    mentions the silver underside of the leaf

Your best source of a TRUE Mexican Sycamore is to find one that was vegetatively propagated.

 

More Trees Questions

Trees for Plum Grove, TX
October 05, 2013 - Sorry Mr. Smarty pants, my question is I live in Plum Grove Texas, I have 5 acres and NO TREES. What trees were on the property were either taken out by Ike, or the twisters that followed. I have boug...
view the full question and answer

Evergreen shrub for hedge in pasture in California
August 15, 2012 - I am looking at putting in a hedge along a pasture between my neighbor and me. I was considering a podacarpus plant about every 4' for 100'. is this a fast growing, full thickness, tall evergreen bu...
view the full question and answer

Slow development in Shumard Oak from Porter TX
April 02, 2013 - We had two Shumard Oaks Planted in Sept of last year (2012). About a month later, they started browning and dropping their leaves (no color change). Now I noticed on one of the trees the buds have sta...
view the full question and answer

Problem with unknown tree in Austin, Texas
July 23, 2013 - Have recently moved to Austin, Texas and have a tree in my backyard that has been dropping leaves and one major branch appears to be dead. That branch has hard rust colored sap circles (about penny si...
view the full question and answer

Transplanting time for Smoketree in Quebec
September 14, 2006 - I would like to transplant my smoke tree. It is two years old. When would be the best time of the year to transplant. I live in Zone 4.
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | JOBS | SITEMAP | STAFF INTRANET
© 2016 Lady Bird Johnson Wildflower Center