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.

Advantages

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.

Challenges

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.

New Seeds for 2014

Since I have been focusing on buying more native perennials from local sources I have scaled back on the number of plants I am starting from seed.  I felt a little guilty about not starting any seeds, then remembered, what about native annuals.  There are quite a few annuals in the nursery trade with native parentage, but in general  finding seed for wild-type annuals can be a challenge. 

Most of the native-derived annuals are from the southern parts of North America, particularly the tropical regions.  The past few years I have mostly been using annuals with North American origins in pots on our deck.

Other than the Ivy Geraniums all these annuals have North American heritage:
Lantana camera, Melanopodium divaricatum, Zinnia 'Profusion' series, Salvia farinacea.

Last year I planted out some native annuals that are also found naturally in the Mid-Atlandtic region, Partridge Pea (Chamaecrista fasciculata) and American Pennyroyal (Hedeoma pulegiodes) as well as some short lived perennials Rudbeckia hirta and Monarda punctata which I started from seed.  I will be watching to see if these will reseed successfully.  What I like about the indigenous annuals is that if they find suitable conditions, they will reseed and fill in gaps in the garden and add spontaneity to the landscape that is lacking with plants that only spread vegetatively.

My first choice is to plant regionally native annuals and biennials.  If suited to the site, these plants will naturally spread to fill open gaps between shrubs and perennials.  My second choice is to use visually appealing annuals from tropical North America like Zinnias and Cosmos, that have a low risk of spreading out of control.  Some of these may reseed in protected locations, but they are unlikely to escape into the wild.  I avoid using North American annuals from other regions (or any plants for that matter) with a high risk of spreading.  You can identify many of those on the USDA Plants database by checking under the 'Legal Status' tab for a given plant.  An example is that California Poppy (Eschscholzia californica ) is listed as an invasive weed in Tennessee.  You can also check the Invasive Plant Atlas.

I've sorted my North American annuals for this year into two groups, those native to or naturalized in Maryland and those not found growing naturally in Maryland.

Native annuals found in Maryland

Plains Coreopsis, Coreopsis tinctoria, is originally from the centrals plains but has escaped and is now found growing across most of the US.  It tolerates a range of soil conditions in full to part sunlight.  It is a good nectar source and is reportedly deer resistant!  The long blooming season (June-Sept.) of golden flowers with red centers makes it a good filler plant.  I have not grown this species before, but from what I've read it looks to be easy to grow. 

This Beach Sunflower grew to about 4 ft in a pot.

Beach Sunflower, Helianthus debilis 'Pan'  is native to coastal areas from Texas to North Carolina but has spread as far north as New England.  It would not be found growing naturally in mountainous part of Maryland where I am located.  This annual sunflower differs from the Common Sunflower (H. annuus) in that it is highly branched and, although the stems are long, at 5-7 feet, it tends bend over and weave into neighboring plants.  The branches are usually mottled with purple or white.  The flower is of the typical sunflower form, though smaller, measuring 2-4 inches across and blooming is from July into October.  It likes full sun and well drained soils.  As expected for the beach, this plant will tolerate salty soils.  It performed nicely for me in pots up in Boston.  This species likes warmer soil for germination which is more easily achieved in planter pots or a raised bed. 

These Sulfur Cosmos are competing
for space with some culinary mint.

Sulfur Cosmos, Cosmos sulphureus  is native to Northern and Central Mexico where it is found in open areas along roads and rivers, in forest openings and pastures.  It has escaped cultivation in the United States and populations have been found from Texas to New York and Connecticut and in California.  This species is listed in as a pest plant in Tennessee and Florida.  In my experience in Boston, this species will reseed itself for a couple of years, then fade out unless some new plants are brought in.  What I like about this Cosmos is that it comes into bloom very early in the summer and that it does not flop over as bad as Garden Cosmos, C. bipinnatus.

After blooming the flowers of this Sneezeweed turn white
and disappear into the foliage. These did reseed
 into the pot the following year.

Sneezeweed, Helenium amarum 'Dakota Gold' grows to about a foot in height and is covered with self-cleaning yellow flowers from early summer to frost.  It is originally a native of the Ozarks but has spread throughout the southeast and as far to the northeast as Massachusetts.  It tolerates dry soils and is also resistant to deer.  When I tried these a few years ago I had excellent germination without any pretreatment of the seed.  The small size and intensity of bloom make this a good candidate for the front edge of a border.

The native ranges of these next two plants actually include the Mid-Atlantic region.

Adlumia blooms from late June to frost.  The shiny black seeds
are easily collected by shaking the dried flowers on the vine.

Allegheny Vine, Adlumia fungosa  is a biennial vine, native to mountain woods of the American East.  I have blogged about this plant in the past.  It's one of my favorites.  This is a true biennial, the first year is spent as a tight rosette of finely divided leaves.  The second year the vine climbs about 10 feet and it blooms with pale pink dangling heart-shaped flowers.  The vine is rather delicate so it needs support and not too much sun.  I have lost some due to the wind causing the plant to twist.  In its native state it often climbs over rocks, rather than scaling trees.  

Miami Mist, Phacelia purshii, is a winter annual that is native to Mid-Atlantic states and lower Mid-West.  It has small, fringed lavender-colored flowers that bloom in spring.  As a winter annual, it needs to get its start in the fall, as temperatures cool and moisture increases.  From what I have read, the seed should be exposed to warm summer temperatures to break the seed dormancy.  So I will direct sow some of these in June and also put some outside in small pots where I can keep an eye on them.  They overwinter as a rosette of leaves, then put forth a flowering stalk the following spring.

North American Annuals Not Hardy in Maryland

These last three plants have not been found growing in the wild in Maryland.

These Bluebonnets were growing at the Lady Bird Johnson Wildflower Center in Austin, Texas.
I doubt I will have such good results in Maryland, but I'll try.

Texas Bluebonnet, Lupinus texensis  is a Texas native and my wife's favorite flower.  I have tried these once before with limited success.  This is due at least in part to the very different growing conditions in the Northeast.  Besides soil composition, it takes much longer for the northern soils to warm up relative to Texas.  On doing a little more reading, I found that it is helpful to inoculate the seeds with the correct bacteria to help with nitrogen fixation.  I found that Prairie Moon Nursery offers a variety of  inoculum for different legumes in small packets at a reasonable price.  Also, the Bluebonnets are winter annuals, like the Phacelia above.  I will plant some seeds this spring, like regular annuals and I will hold some back for fall planting.  My concern is that our winters may be a bit too cold for them to survive.  Anyway, we have a little garden for Texas plants (south-facing, drier soils) and we'll see what happens. 

Spanish Flag, Ipomoea lobata, is an annual vine from Mexico that grows to 5-10 feet.  I found no records that show it to be self-sustaining in the contiguous US.  It produces racemes of tubular flowers in mid-to-late summer that change from red to orange and then white as they mature.  These flowers are favored by hummingbirds.  I've seen  this vine used to quickly cover a chain-link fence.  When starting from seed, scarification and presoaking in warm water is recommended.

Texas Sage blooms from late July to frost.

Texas or Hummingbird Sage, Salvia coccinea, is native to the southern states. But I've had it reseed in Boston for several years in protected locations. I've grown it successfully in both pots and in a raised bed.  I like the taller more open form of this red Salvia compared to the heavier dense blooms found on the commonly available annual Scarlet Sage, S. splendens.  

As I recall, bumble bees would get nectar by landing on the top of the flower and sticking their tongues into the calyx tube at the base of the flower.  It will be interesting to see how our hummingbirds approach this flower.

Spring Wildflowers: Texas vs Maryland

Two weeds ago we made a trip to Texas to visit family.  The end of March is the beginning of Texas wildflower season.  We flew into Austin then drove up to the Ft. Worth area.  You could see that Austin was really coming into bloom.  As we drove northward along I-35 the number of Bluebonnents along the highway dropped off considerably.

Even at 75 mph you can appreciate Texas Bluebonnets

One thing about seeing wildflowers in Texas is that they come in big patches.  Much of this is due to the efforts of Lady Bird Johnson with the Texas Highway Department to create and preserve wildflower habitats along the highways.

View of Courtyard at the Wildflower Center in Austin, TX

When we got back down to Austin we paid a visit to the Wildflower Center.  Here we saw many of the wildflowers we saw along the highways, but this time with handy name tags.

Texas Bluebonnets at low speed.

There are about 50 species and subspecies of
Indian Paintbrush (Castilleja).  I don't know
them well enough to tell them apart.

I've been looking for seeds for Groundsel.  This looks like it would be a nice addition
to a low-growing meadow/lawn alternative.  It has bright yellow flowers in spring
emanating from a basal rosette of leaves.

This Blackfoot Daisy is found on dry well drained soils.
I was interested in growing this plant, but the Northeast
does not provide the best conditions.

This little Prairie Verbena was all by itself, but it is known to
grow in large swaths, turning the ground purple. 

The narrow bronzy-green leaves of this Spring Beauty
blend into the leaf litter.

On our return to Maryland, the landscape was just beginning to turn from brown to spring green.  However, there were no massive swaths of color as we had witnessed the day before.  Inspired by all those Texas flowers I took a walk through the woods and found a few subtle surprises.  There were little pinkish white flowers along the edge of the woods.  These turned out to be Spring Beauties, Claytonia virginica.  This ephemeral perennial blooms in early spring, then essentially disappears after setting seed.



Further into the woods I found the masses of Toothwort continuing to expand.  The buds still have not opened, but they are nearly ready.

It's early April and these Toothwort are nearly ready to bloom.

The latest find was masses of finely cut foliage indicative of the genus Dicentra.  I searched around for a while and found one clump with developing flowers.  I'm pretty sure that these are D. cucullaria, Dutchman's Breeches.  I will keep a watch out for other family members, like Squirrel Corn (D. canadensis) and Wild Bleeding Heart (D. eximia).  These are most easily distinguished by the shapes and colors of their flowers.

When the flowers of Dutchman's Breeches are fully developed
they look somewhat like upside down pantaloons.

  

 I'm not keeping score, but the spring wildflowers in Texas are a grand sight to behold, but when the early summer temperatures creep into the 100's they will disappear.  In the Northeast the ephemerals will also slowly fade from view, but this will be due to the developing shade of the woodland canopy rather than the heat and dryness.  No matter where you live you've got to get out and appreciate that winter is coming to an end.