Thursday, June 13, 2019

Designing with Native Plants

Designing with native plants is not that different from designing with any other plant palette.  You still use basic design concepts, using the shapes, colors and textures of plants to create rhythm and flow in the landscape.  What is different is that your selection of plants is more focused on native species, ideally ones that are regionally or locally native.


What you gain from using native species in your landscape is greater benefit to the nearby wildlife, better fit with the local ecology and character of the region, and, if your plant selection was right lower maintenance and increased sustainability.

There are North American native plants species that will grow under just about any landscape situation imaginable.  That doesn't mean that any North American plant will grow anywhere in North America.  Beyond the many geographic climate zones there are also differences in soil chemistry, texture, moisture, exposure to sunlight and competition both from other plants as well as animals.

By looking at nearby native plant communities you can get some inspiration about what to combine in your landscape.  At Mount Auburn Cemetery in Cambridge MA they created a meadow using many species of grasses and wildflowers native to the Northeast. 

This constructed 'Northeast Meadow' features showy goldenrod (Solidago speciosa),
little bluestem (Schizachyrium scoparium), New England blazing star (Liatric scariosa), hyssopleaf thoroughwort (Eupatorium hyssopifolium) and brown-eyed Susan (Rudbeckia triloba).

When I was designing a planting for a sloping path I selected some species that I observed along a nearby hiking trail in Maryland Heights.

Bottlebrush grass (Elymus hystrix) and clustered mountain mint
(Pycnanthemum muticum) are major components of this hillside garden.

While I stress about how you need to match plants to their ideal conditions, there are often surprising exceptions.  Test their adaptability by trying a plant or two in unusual locations, they just might catch hold.  This is why I like to use natives that produce a lot of seed, particularly native annuals.  The seed is able to spread around and find new places to grow, some of which will be a good fit.

This pink tickseed was originally planted in a near-by bed but found a better home when seed fell into a crack in the driveway.


Some natives are generalists and are able to grow well under a wide variety of conditions.   Others are more specialized, having adapted to some very specific growing conditions.  Some of the frustration of working with natives is that while it is implied that they are adapted to grow in North America, a given native will not necessarily do well everywhere on the continent. 

Another factor to realize is that residential landscapes often have very different soil conditions than near-by natural areas.  Depending on where they are located around a building, light exposure and moisture levels can also be very different from undisturbed areas.  Newer construction areas often have compacted soils.  Many times the native top soil has been removed and replaced with soil from another location.

Reasons for failure of new plantings include competition from other plants, incorrect soil chemistry, texture or drainage, or missing  companion plants.  Also consider age of plants and the original conditions when they were planted.  Many shrubs growing in shade were planted when there was less competition both for light and root space.  Planting new specimens into an established wooded area is more challenging now than when the area was originally planted.  I have been fooled into planting new rhododendrons under established shade trees based on seeing mature shrubs in woodland settings.  In many cases, there is too much competition in the root zone for water and nutrients and too much shade cover for the new plants to get established.  Options here include opening up or raising the tree canopy, clearing a wider root zone (without damaging the existing trees), or  opting for more shade tolerant species.

Sometimes when I see native species dominating some harsh environmental conditions and I think, wow that could grow anywhere.  That is often faulty reasoning.  In many cases these plants excel because they have adapted to those conditions in specific ways to use those harsh conditions to their advantage to out compete other species.  

Rock harlequin will excel in thin rocky soils but does
 not compete well in normal soils against other plants.

One example is rock harlequin (Corydalis sempervirens) a short lived perennial that needs to reseed itself to maintain a garden presence. It's native to rocky slopes in the Northeast where there are shallow pockets of soil and exposure to full sun for a good portion of the day.  When planted in richer soil or 'better' conditions it often fails due to competition from other plants. 

Almost all plants in nature grow in a community of some sort.  There are a few  species that require a host plant to help them grow and develop.  Indian paint brush (Castilleja sp.) tap into the roots of neighboring plants, such as little bluestem or penstemons, for nourishment.  False foxgloves (Aureolaria sp.) are partially parasitic on the roots of oak trees.  And , like many members of the pea family, Texas bluebonnets (Lupinus texensis and sp.) do better when there are specific soil bacteria present to help them fix nitrogen. 

Texas bluebonnets are winter annuals that blanket open fields with their iconic blue and white flowers in early spring.  They are well adapted to the calcareous soils with the assistance of a soil bacteria.  Performance in other regions is erratic. 

Plant Selection and Sources

The nature of native plants are that they are native to particular areas of the country based on climate, soil chemistry and evolutionary history. As such there are very few 'nationally native' plants, nor should there be.  If you search the garden centers you can often find sections devoted to native plants.  The nice thing about many commercially available native plants, though there may not be many of them, is that most have been selected to be commercially viable, that is they work in many residential situations and are fairly robust.  We need to expand the offerings by asking for more of these plants.  American Beauties is one program based in the Northeast that is supplying a variety of native species.  There are also a number of native plant suppliers that you can find on the web.   Izel Plants is a clearing house for a number of native plant nurseries primarily in the Eastern US and has an extensive catalog of native species.  The Plant Native link below also has listings of native plant nurseries by state.   You can also search the web for nurseries in your region that specialize in native plants. 

To help with the selection of which species to use there are a number of websites that allow you to search for plants based on the site conditions.  You can find plant search websites for a given area by using search terms like 'Native Plant Database for  '  My favorite site to search is from the Wildflower Center.  It allow you to search by where a plant is native as well as specific growing conditions and plant attributes such as size and bloom color.  Plant Native is another good site.  While the plant lists are smaller, the plants listed are mostly commercially available.  Missouri Botanical Garden has an excellent search platform, but it is not solely native species.

Strategies for Designing with Native Species

  • Try to match the preferred conditions/habitats of a new plant to your local conditions (much easier than trying to match your conditions to those of a given plant).
  • Start small, when in doubt.  Before doing a massive planting put in a couple of plants as a test to see if they survive.
  • Try a new species in a couple of different locations to see where it grows well. 
  • Don't just drop a new plant into an established bed.  Clear some area to allow for roots to get established without competition.  Also open up the canopy to let in some light.  Water well, but don't feed perennials, shrubs or trees until the roots are established (about one growing season).
  • Build a plant community by learning about which plants grow together in nature.
  • When starting perennials from seedlings, like you get with liners or sizes one quart or smaller, it will take as many as three seasons for them to reach their full glory.  The adage 'sleep, creep, then leap' really does hold true when start from small specimens.

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