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Epiphytes
& Parasites
The much-maligned ball moss,
Tillandsia
recurvata, is actually a bromeliad, related to pineapples and the brilliantly-flowered
exotics seen in greenhouses. Bromeliads can be terrestrial, saxicolous
or epiphytic. Terrestrial species grow, like most plants, with their roots
in the soil. Saxicolous ones grow on rocks and epiphytes grow on other
plants.
Epiphytes are not parasites;
none draw any nutrients directly from their hosts. The advantage bromeliads
gain from their arboreal perch is height. They are elevated beyond the
reach of most browsing animals and receive more sunlight for photosynthesis
than they would if growing on the ground in a tropical forest.
Why is it, then, that ball
moss is thought by many to be a scourge worse than mistletoe? Primarily
because of a misunderstanding regarding how trees grow and eventually lose
their lower branches. Look closely at the trunk of any large tree and you
will notice circular patterns in the bark with indicate the positions of
long-dead branches. Throughout its life, a tree is forming new branches
at its growing points and killing its lower ones. Branching occurs to disperse,
both efficiently and uniformly, the sunlight-catching leaves throughout
the canopy of a tree.
Limbs die naturally when
their leaves cease to produce enough nutrients because shading has impaired
their ability to photosynthesize. At any time, a mature tree can be expected
to have several limbs in the interior of its canopy in various stages of
decline, and others dead and decaying. In the absence of ball moss, such
a scene does not beg for fantastic explanations.
Now comes the innocent ball
moss seed, propelled by wind away from the flower spike where it formed.
Most seeds land on inhospitable sites, never to grow. A very few become
tangled in the bark crevices of a limb somewhere within a tree's canopy.
In such a site, protected from too much sunlight, they germinate and grow
to maturity if rainfall and atmospheric humidity are sufficient. The ball
moss will thrive until the branch supporting it falls due to death and
decay.
In general, ball moss grows
best in the interior of trees where it is shielded from the sun's drying
rays. In sites where relative humidity is ample, ball mass can spread to
the upper reaches of a tree and even onto electrical wires or fences. This
phenomenon can be seen near Pleasanton and in some of the narrow river
valleys in the Hill Country.
There are still those who
assert the contrary position, claiming ball moss is detrimental to trees.
Another answer to those skeptics is to point to large, old trees, whose
dying, interior branches are fully clothed with ball moss and then inquire
how such a tree, a paragon of its species, could ever have achieved its
lofty status having spent the last 200 years "encumbered" by that native
epiphyte?
If one wished to proceed
further with such a line of reasoning, one might also inquire of the skeptics
how it happened that any tree was able to live to maturity before this
area was civilized and its woods "freed" from the "ravages" of ball moss?
Will they answer that the aboriginal Americans spent their days as compulsive
arborists busily plucking every single clump of ball moss?
If your trees are healthy
and actively-growing and you cannot stand the sight of ball moss, just
prune out the inner dead wood. Chemical sprays are used by some to kill
ball moss, but because of its tenacious roots, it will remain, dead and
very ugly, on the tree for up to three years until it decays.
If your trees are declining
and have more ball moss than your neighbor's trees, pay an arborist or
horticultural consultant to determine the real cause of their malaise.
Just removing ball moss from sick trees will not cure the underlying problem.
Some "arborists" will still
attempt to persuade you to spend large sums to remove ball moss. They do
so for personal pecuniary advantage and not for the benefit of your trees.
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