By Donna Porter

Early November in our lil’ piece of paradise has re-enforced the fact that Mother Nature “rules” – and, sometimes, with an iron fist.  Rainfall reports recorded by our friend Alexander Walker, out near Naranjito, came in with astonishing, record-breaking amounts.  Alexander recorded that 49.5 inches (123.75 centimeters) of rain had fallen from 11-1-10 to 11-6-10.  That is 4.1 feet (1.21 meters) of rain in 6 days! The highest amount for that week was recorded on Tuesday, with 14” (35cm) of rain.  Thank goodness it doesn’t snow here.

With these incredible rainfall amounts, it is not difficult to comprehend why we have witnessed such destructive effects as roads and bridges collapsing, towns evacuated due to overflowing rivers and numerous landslides.  Natural catastrophes are happening worldwide, and for the most part, there is not a darn thing that we can do about it, except…… to tread more lightly on our dear “Mother”.

Development and Nature have been at odds for the last century.  Developers sometimes seem oblivious to the fact that their decisions have more of a direct effect on our earth compared to many other professions.  Here, in our area of Costa Rica, we are blessed with an absence of industry and its ill effects, with the exception of agriculture, which certainly has its own detrimental impact on the environment and its people.  We can only hope and pray that the wiser, more conscientious  and less greedy sustainable developers will soon take the lead in Costa Rica and that stricter development regulations will be honestly enforced.

On a smaller, more personal, individual scale, we, as caretakers of our earth, can always do our minute part in keeping our planet healthy and intact.  Things like recycling, carpooling, using public transportation, utilizing organic or less toxic pesticides – are all things that we have been aware of, and hopefully practicing, for decades.   But, being a conscientious landowner is one of the greatest contributions you can make to your community and the entire planet.  Doing your part to prevent soil erosion should rank high on your “do the right thing” list.

In the plant world, there are 2 classifications of plants – dicots (trees, shrubs, vegetables, etc) and monocots (grasses, bamboos, palms).  Amongst other differences, dicots typically have a dominant tap root with numerous thick and thin lateral roots extending from it.  Monocots have fibrous root systems with adventitious roots that extend from other parts of the plant, like the stem above the soil level, rather than from one main tap root below the surface.  These fibrous root systems (especially some grasses) are quite extensive and massive, consisting of millions of tiny roots that create a thick, almost impenetrable clump that can be nearly impossible to eradicate.  Soil particles cling to these roots and are excellent in preventing soil erosion.

Vetiver, Chrysopogon zizaniodes, is the all-star, tropical grass that is used for soil erosion and soil stabilization and is available in our local nurseries, usually sold as bare-root clumps.  This thin –bladed, clumping grass grows 1 – 1.25 M in height, but the amazing part is that its roots can grow to a depth of 2-4 M in only a few years time.  Vetiver is a non-invasive, sun-loving plant and when planted in a row with spacing of about 1M, it can form an impermeable, solid line that blocks surface run-off. Other grasses commonly used in soil erosion are Lemon Grass. Cymbopogon citrates and Citronella, Cymbopogon nardus.  Most tall grasses possess these long fibrous roots. Grasses used for sod/lawn purposes have very shallow (3-5”), fibrous root systems that grow more horizontally than they do vertically.  They serve more as a ground cover than they do as a soil stabilizer.

Another famous monocot that grows even faster than Vetiver and is used extensively for soil stabilization along riversides, in deforested areas and in earthquake prone areas is Bamboo.  Along with its voluminous, net-like root system, research has also shown that the leaf shape of bamboo reduces the force and the impact of heavy rains upon the soil (more so than grasses do) thus additionally minimizing erosion.

Palms, which are also monocots with fibrous root systems, have been used successfully along the seashore for soil stabilization.  Geo-textile mats, made from coir (coconut fibers) and from palm leaves, are gaining in popularity as soil protectors.

A combination of all of the above monocots, along with a fast growing ground cover such as Lupito, Dissotis rotundifolia, would greatly help to stabilize a hillside within 1-2 years time.  Additionally, some of our native plants like Heliconia latispatha, have thick, rhizomatous-type roots, and will strengthen the surface of a hillside.  Vetiver, though, will provide the deepest  and quickest penetration of roots into the depths of the soil, at least, that is, to whatever depth the rock layers lie below.

A Bamboo collection is included in the Conceptual Plan for the botanical garden.  This collection will serve to increase the limited number of tropical species and varieties of Bamboo currently available and sold in nurseries in our area.  For erosion control, some species work much better than others. It is best to research, and possibly purchase, the best bamboo for this purpose, on-line.

Donna is a Horticulturist and has been living and working in Manuel Antonio for 7 years.  She consults, designs, installs and maintains gardens for private homes and hotels and also develops botanical trails. Donna is the founder and first Director of the Botanical Garden of the Ozarks and is pursuing the development of a botanical garden in, and for, the Quepos area. dpdreamer@yahoo.com,  2777-5149

Filed under: Donna Porter, It's a Wonderful World of Plants on December 16th, 2010
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