Mexican Olive Tree flowers and fruit--hey, it's not really an olive!
Mexican Olive Tree at the Alamo flowers and fruit
Monika Maeckle

by Monika Maeckle

The 17 Rangers who patrol the grounds of the Alamo have a favorite place to hang out on the plaza:  under the shade of the Mexican Olive tree that graces the mission’s north wall.   That’s understandable since the dense shade of the flowering, 19-foot specimen reduces radiant heat from surrounding rock walls and walkways by as much as 12 degrees.

Mexican Olive Tree flowers and fruit--hey, it's not really an olive!
Mexican Olive Tree at the Alamo flowers and fruit

Considered a small tree that reaches 25 – 30 feet, the Mexican Olive, or Anacahuita, is more frequently seen south of San Antonio because it can’t take a hard freeze.  Despite many shared traits and similar names, the Anacahuita and Anaqua trees should not be confused.  They both exhibit stellar flowers, small fruits, and a high tolerance for drought, yet are two completely separate species living in the northern reaches of their natural range, said City Forester Michael Nentwich.

The Alamo’s particular Mexican Olive, in fact, died back to the ground–twice–once in 1983 and again in 1989, said Alamo horticulturist Mark Nauschutz.  For years it had twin stems, which were reduced to a single trunk two years ago when its branches reached across a walkway, brushed  up on the Alamo wall, and blocked passage.

The surviving sibling seems to be thriving.  “This species is truly a survivor,” said Nentwich.  “I’m impressed with its longevity in such harsh conditions.”  Nentwich pointed out the impervious walkways and heat-radiating limestone walls surrounding the tree. Nauschutz added that the tree has not been watered in 15 years.

Mexican Olive Tree at the Alamo
Mexican Olive Tree at the Alamo

The Anacahuita sports fuzzy leaves with delicate hairs, a classic adaptation of xeriscape plants.  The fine fur helps conserve moisture. White, showy flowers provide nectar to moths, butterflies, and bees.  The tree also plays host plant to the Mexican Olive beetle.

The Mexican Olive yields small, yellowish fruits beloved by birds, squirrels, even livestock.  People may want to avoid the fruit, which may cause dizziness and/or indigestion.  “It might give you the squirts or make you sick if you don’t cook it first,” said Michael Nentwich.  For your own Mexican Olive tree, simply plant one of the fruits.   The tree grows fast and requires little care once established.

Interestingly, the Mexican Olive technically is not even an olive tree, but a relative of the forget-me-not, a flower associated with loved ones’ never forgetting each other.  How appropriate for remembering our Alamo.

The Mexican Olive at the Alamo

Species: Cordia boisieri

Height:  19 feet

Canopy:  24 feet

Diameter at breast height:  9 inches

Circumference:  2 feet, 4 inches

Age:  Probably around 50 years

Location:  Alamo Plaza, north wall, in front

Get there by bus:  Blue Route or Yellow Route.  The Alamo is a main bus stop, and buses run every 15-20 minutes.

Also known as: Wild Olive Tree, White Cordia, Texas Wild Olive, Anacahuita

NOTES:  Diameter at breast height, or DBH, is a standard of measuring tree diameter at four-and-a-half feet off the ground.  Regarding the age of trees, arborists and foresters are reluctant to cite them.   The only accurate way to determine a tree’s age is with an increment boring test, whereby a hollow drill bit is bored into the tree trunk.  Very traumatic for the tree.  Since soil and water availability determine tree growth, some trees grow huge in several decades while others live  a century and can be much smaller.  The tree’s temperament is also a factor.

In short, when it comes to determining tree ages, size doesn’t matter.    We will cite educated guesses by certified arborists for the ages of featured trees, unless scientific or historical data are available.

Have a favorite heritage tree?   Send us a photo, a story and we’ll consider it for inclusion to hello@rivardreport.com.

More on San Antonio’s trees:

San Antonio’s Initiative to Plant One Million Trees by 2020

Read our weekly series on Heritage Trees.

Monika Maeckle writes about gardening, butterflies, conservation and the Monarch butterfly migration at the Texas Butterfly Ranch.  She covers nature in the urban environment for this website.  You can reach her at monika@therivardreport.com or follow her on Twitter @monikam.

Monika Maeckle

San Antonio Report co-founder Monika Maeckle writes about pollinators, native plants, and the ecosystems that sustain them at the Texas Butterfly Ranch website. She is also the founder and director of...