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Friday, October 1, 2021

Madrone Mysteries

 

Texas Madrone

A striking small tree, to 30 feet, the Texas Madrone (Arbutus xalapensis) occurs in protected canyons and mountain slopes of Big Bend, but its range extends eastward to the Edwards Plateau in Travis County.  It is a rare native tree, but can be locally common in the right habitat, preferring grasslands and open oak-juniper woodlands on rocky limestone slopes. Its simple, pointed oval, leathery leaves, 2 to 5 inches long, are evergreen and medium green on top and lighter beneath.  In spring, clusters of small, fragrant, bell-shaped white flowers appear above the leaves, developing into bright red-orange fruits in late fall.  These fruits are relished by many species of birds and mammals and are reported to be edible by humans.

Texas Madrone flower cluster

One of the first mysteries of the Texas Madrone is its bark.  Bone-white and smooth when young, with age it becomes scaly and turns to shades of pink, red, and brown. This older bark peels away in patches and strips, revealing a smooth reddish bark underneath, and gives the tree some of its more colorful, old colloquial names such as Lady’s Leg and Naked Indian. But why does the bark exfoliate?  The most commonly accepted theory is that it is an evolutionary development to rid the tree of lichens and parasites such as wood boring insects, preventing their buildup and reducing the chance of disease.

Peeling Texas Madrone bark

Ashe Juniper nurse tree
protecting a young Texas Madrone

While it is one of the most interesting and beautiful native trees of Texas, another mystery of the Texas Madrone is that it is extremely temperamental to grow.  Its propagation requirements are complex, and it is very difficult to successfully transplant from the wild.  Madrones have a fine root system that is easily damaged, and even slight root damage is usually fatal to the tree.  Additionally, new seedlings require the protection of a ‘nurse tree’ to become established.  A nurse tree is a larger, faster-growing tree that safeguards the seedling while it gets established by providing shade, shelter from the wind, and protection from grazing animals.  For the Texas Madrone, its nurse tree is most often the native Ashe Juniper (Juniperus asheii). Adding to its temperamental nature, this tree is slow-growing, taking more than a century to attain a fully mature height.

Texas Madrone fruit

Texas Madrone trees flower from late February to early March, while their fruits don’t mature until late November to late February.  Like several species in the genus Arbutus, the fruits begin to form in mid-spring but fruit development is delayed for several months so that the next spring’s new flowers begin to appear while the previous year’s fruits are ripening.  This timing delay results in a short period of time when both fruit and flower can be simultaneously present on a tree, yet another intriguing characteristic of the mysterious Texas Madrone!