Rare Plants

Hueco Tanks is home to several plants that are relics of the last ice age.  At the time these plants appeared in the area, the weather was much cooler and there was a lot more rain than there is now.  Today these plants, which are all trees or shrubs, still thrive in the park but are not found in the immediate surrounding areas.

The first of these is the Arizona White Oak (Quercus arizonica), which is a type of live oak. This means that it keeps its leaves year round, only shedding them during drought as a means of protecting themselves.  Dropping the leaves is an adaption which helps to reduce moisture loss, a very important key to survival in the desert environment.  A number of these trees are quite large.

The second tree is the Roseberry Juniper (Juinperus coahuilensis).  It, too, is not found in the general area surrounding the park.  There are conflicting reports as to whether or not this tree is still reproducing.  However, the trees in the park all appear to be healthy.

The third relictual species is another tree:  the Netleaf Hackberry (Celtis reticulata).  These can be seen in multiple areas of the park.  They will grow out of cracks in the rocks, and they live for a very long time.  On the path to Comanche cave there is a huge one that must be at least several hundred years old, given that they grow slowly.  The fruit of the Hackberry hangs on the tree over the winter, and is enjoyed by birds.  People have been known to make jelly from the berries, although they are not something we would eat straight because they are mostly seed.

The last of the relics of the ice age, and the only truly rare plant in the park, is the shrub Erect Colubrina, which is truly a relic of the ice age.  When you look at it, the first thing that is evident is that it couldn’t possibly belong in the desert.  Desert plants generally have stiff leaves and waxy coatings, that minimize water loss in the hot, dry desert climate.  Other plants, such as cacti, have leaves that have been so far modified that they are no longer recognizable as leaves.  The ocotillo’s solution to minimize water loss is to grow leaves only immediately after a rain, and then drop them several weeks after the last rain.  The desert ferns mostly have the stiff leaves covered with scales.  Then there is the Erect Colubrina, also known as  Comal Snakewood:  it has large, soft, fuzzy leaves that belong in a moist climate.  It is a testament to the amount of water present at Hueco Tanks that this shrub still survives, even  though there are very few left.  Because these plants are so fragile and so rare, people are allowed to see them only once a year, on a guided tour during the weekend of the Interpretive Fair.  What makes the Erect Colubrina so special is that this small population at Hueco Tanks is the only place it is known to grow in the United States.  

Erect Colubrina has been an interesting lesson in how plants adapt to life in the desert.  When the climate is very hot and very dry, the shrub survives by shedding a lot of leaves, and growing only very small ones.  Those small leaves will fold up to reduce the amount of moisture lost.  In 2017 we saw it in bud in June, but then the buds dried up due to extreme heat and dryness.  But after a few inches of rain, we discovered in July that it was not only budding out again, but actually flowering.  A photo of the flowers is here.

Rare plants may also be found in the form of plants with a very limited range where they grow.  Examples of these are the El Paso Pincushion Cactus, the Sand Prickly Pear, Desert Pincushion Cactus, Sneed’s Pincushion Cactus and the Eared Holly Fern, all of which are detailed in other sections of this blog.

The final category of plants that might be considered rare are plants that one would not expect to see growing in the desert.  This includes plants that need a lot of water, such as the Cottonwood Tree, Drummond’s Clematis, any of the xerophytic (dry climate adapted) ferns, moss and spikemoss (a type of club moss) and the Ferriss Scouring Rush.

All of these plants survive at Hueco Tanks because it is a true desert oasis.

© Susan L. Stone 2015                   rovingstones@me.com