Artilcle for Use: Landscape Design with Native Plants

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on: January 09, 2008, 09:53:26 AM
Landscape Designs with Native Plants
by  William Bissett

Over the last fifteen years as a student of landscape architecture, apprentice landscape architect, and finally as a registered professional, I have held a belief that plants native to an area should be used to heal the wounds of land development.
The last 75 years or so, with plant imports to this country from all over the world captivating everyone’s attention, our landscape has become the domain of botanical curiosity rather than environmental healing.  Combining that with our desire for the eclectic European “estate” or “villa” aesthetic, we have what I call “constructions by destructions”¬—i.e., the clearing of all natural plant material within the corner stakes, to replace it with high-maintenance and low-environmental-benefit turf grass and exotics. 
My years as a professional have been spend trying to get native plants back into the disturbed landscape.

A few important things need to be considered when going back to native plants.  First, of course, is that preservation of the existing ecosystem at all costs, on any site, is priority one.  No removal of existing natural material means no habitat loss, no destruction of top soil or loss of mycorrhiza, no loss of erosion control, and no explosive weed growth.
For land that has been previously disturbed, however, I believe the replacement of native plant material is the best we can do.
 Secondly, without a concept, theme, or goal, we may not we may not accomplish a great deal.  I put native plant use in three different landscape categories for the sake of definition: traditional, naturalized, and restorative.  These categories make the design of a project a more understandable task. 

   Native plants in a traditional landscape is the easiest to accomplish and the most commonly done, and sometimes without the knowledge of anyone involved.  The obvious examples are the scores of pines, oaks, wax myrtles, and counties that are planted every day.  Believe it or not, there are times when landscaper, landscape designer, and ever the nurseryman that grew them didn’t know they were working with native plants.
But besides the obvious species, almost any native plant from the mesic range (neither wet or excessively dry) can be substituted for a commonly used exotic in a traditional landscape.  For instance, blackhaw viburnum (Viburnum obovatum) can be substituted for ligustrum as a large screen or hedge; Virginia willow (Itea virginica) or shiny lyonia (Lyonia lucida) for masses of pittosporum; or blue-eyes grass (Sisyrinchium atlanticum) for masses of liriope.
Whatever the species used, a traditional landscape will have some general characteristics, such as:
•   More formal appearance,
•   More repetition and less diversity,
•   Fewer species,
•   More turf grass, and
•   Most likely extensive irrigation, and no reduction in maintenance or water use.
Native plants could be interchanged with exotics with no real ecosystem/species convergence.
The real benefits from using natives in a traditional landscape are the certainty of cold-hardiness, the possible reintroduction of habitat elements, and the satisfaction of replacing lost genetic material to the site.
There is certainly nothing wrong with giving native plants traditional usages.  They can make beautiful specimens, mass plantings, accent planting, borders, and foundation.  But we have to realize that we have not necessarily reduced maintenance or water demand , or improved the ecology of the area appreciably.  To do that we must start thinking more naturalistically.

   John Simons in his book, Earthscape, says, “Natural systems tend toward equilibrium or condition of least imbalance and minimum stress.”  Landscaping a disturbed site in a more naturalized way can start to accomplish the dual role of built, people environment and natural habitat.
   Here again, there are some general characteristics of this concept that should be understood, such as:
•   Less formal appearance,
•   Looser looking,
•   More diversity and greater number of species,
•   Plants not used in traditional ways, i.e., specimen, hedge, border,
•   Mass plantings used as special definition,
•   Little or no turf grass,
•   More ground cover or open mulch,
•   Irrigation and fertilization not needed on regular basis after establishment,
•   Species used are indigenous to site ecosystem or those of similar characteristics,
•   Additional habitat and less maintenance, and
•   May still contain compatible exotic species without loss of goals.
The most important things to remember when designing any landscape __ but especially a naturalized one—is to used plant material where it will be able to attain maturity comfortably and will not have to be trimmed back to allow for circulation or other activity.  Also remember that chance in the landscape is normal and good.  Self-seeding, colonization, and/or perennial movement of species should be allowed.

   The last category of native plant landscape use is restorative.  This concept is in more critical need as the site becomes more extremely hydric or xeric.  It is a crime to drain or fill wetlands to a mesic level, and I feel it should be a crime to irrigate and/or amend the scrub ecosystem to make them supportive of mesic plant material.  Even a mesic native plant becomes an exotic when used on a site that would make constant irrigation a necessity.
   Here are a group of characteristics common in the restorative landscape:
•   a very complex pattern (mimicked from an existing natural ecosystem, if possible),
•   large number of species, all of which are indigenous to that site ecosystem,
•   asymmetric balance of site elements,
•   small changed in topography of hydrology reflected by the species change,
•   uneven or random spacing,
•   no relationship of plantings to site structure, i.e., mass plantings to define space or circulation patterns, framing, etc.,
•   must have dead material as well as natural ground litter,
•   no exotic species allowed,
•   no irrigation at all after planting,
•   no soil amending at all, other than cleanup of construction debris.

Any attempt at restorative landscaping takes not only a great deal of understanding, but also a tremendous amount of time and patience.  As John Simons says, “The natural ecosystem is not only more complicated than has previously been understood, it is more complicated than we yet can comprehend.”
   Unfortunately, we see landscape architects and engineers designing natural ecosystems (restoration mitigation) with sometimes no more than a single phone call to a native plant nursery as their background.  This will change as knowledge and experience replaces speculation in the professional market.
   While there will never be a true restoration of ecosystem, the word mitigation has become “dirty” in the environmental vocabulary.  There remains a critical need for the best attempts in repairing destroyed ecosystems.  This is true on any scale, from regional mining to residential lots.

This article was first published in Lake Region Naturalist, 1988-89, publication of the Lake Region Audubon Society.  Reprinted with permission. 
Karina Veaudry