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Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

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Sunday - August 18, 2013

From: Elmendorf, TX
Region: Southwest
Topic: General Botany, Plant Identification
Title: How does Styrax youngiae differ from other Texas Styrax species?
Answered by: Nan Hampton

QUESTION:

How does the Styrax youngae differ from other Texas styrax? Where can I find a description of all the Texas styrax trees?

ANSWER:

First of all, Styrax youngiae is no longer a separate species.  It is now designated as a subspecies, Styrax platanifolius ssp. youngiae (Young's snowbell), of Styrax platanifolius (Sycamoreleaf snowbell).  Here is the Texas county distribution map from the USDA Plants Database.  There three other subspecies as well:

Styrax platanifolius ssp. texanus (Texas snow-bell)  Here is the Texas county distribution map from the USDA Plants Database.

Styrax platanifolius ssp. platanifolius (Sycamoreleaf snowbell)  Here is the Texas county distribution map from the USDA Plants Database.

Styrax platanifolius ssp. stellatus (Hairy sycamore-leaf snow-bell)   Here is the Texas county distribution map from the USDA Plants Database.

There are also two other species that occur in Texas:

Styrax americanus (American snowbell)  Here is the Texas county distribution map for the USDA Plants Database.

Styrax grandifolius (Bigleaf snowbell)  Here is the Texas county distribution map for the USDA Plants Database.

You can see a description of the Genus Styrax in the eFloras.org (Flora of North America) database.  You can see that S. platanifolius does not have axillary flowers; whereas, S. americanus and S. grandifolius both have at least some axillary flowers.  The difference between S. americanus and S. grandifolius involves differences in the length of the calyces and corolla tubes as well as the type of fruit.

Next, to see the differences between the different subspecies, go to the eFloras.org page for S. platanifolius and you will see that S. platanifolius ssp. platanifolius and S. platanifolius ssp. stellatus has the abaxial surface (the underside) of the leaves mostly glabrous (without hairs) or at least visible through the hairs; whereas,  S. platanifolius ssp. texanus and S. platanifolius ssp. youngiae have their abaxial surface covered in pubescence (dense hairs).

S. platanifolius ssp. texanus has glabrous (without hairs) leaf blades adaxially (on the upper leaf surface) and S. platanifolius ssp. youngiae has stellate pubescence (star-shaped hairs) on the adaxial leaf surface.  There are also differences in pubescence on stems and other structures.

 

From the Image Gallery


Sycamoreleaf snowbell
Styrax platanifolius ssp. platanifolius

Hairy sycamore-leaf snow-bell
Styrax platanifolius ssp. stellatus

Texas snow-bell
Styrax platanifolius ssp. texanus

Sycamore-leaf snowbell
Styrax platanifolius

American snowbell
Styrax americanus

Bigleaf snowbell
Styrax grandifolius

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