Wednesday, February 24, 2010

Creating Native Plant Communities

Many contemporary gardens are artful compositions designed to show off beautiful plants and elicit an emotional response. A main goal is that these compositions be ‘readable.’ This often requires that the ground plane be a smooth, weed-free layer of mulch. The ecological function of the plants and their interrelationships are not of primary concern. A more naturalistic approach to landscape or garden design puts a greater emphasis on the ecological function of the garden; this includes a well functioning plant community.

In a plant community there are plants to fill all available spaces, to the extent that the soil and moisture conditions allow. The spaces are filled on both a spatial and a temporal basis. There are different plants growing and receding over the course of a year. For example, one spot may be occupied by a wild geranium in the spring, followed by a big-leaf aster later in the summer and into fall, and all this could be happening beneath a shrub or small tree. The benefits of the diverse community of plants is that the ground is always covered, which blocks out weeds without the addition of a layer of mulch. These plant layers also provide cover for many beneficial insects – reducing the need for pesticides.
Another huge advantage of working with plant communities is that all these plants grow under very similar conditions. So soil conditions, water needs, climate and light requirements are all consistent and you don’t need to fuss over any individuals in the garden.

Designing a Plant Community

In nature, plant communities eventually develop on their own. In the residential garden we can play a role in what that community looks like. The first step is to determine the type of habitat you will be working with. Edith Roberts and Elsa Rehmann in American Plants for American Gardens, first published in 1929, taught about designs that were sensitive to the site and how to use appropriate natural plant communities in those landscapes. They describe habitats and provide lists of plants appropriate to rural Connecticut.

Another book with more emphasis on the design process is Natural Landscaping – Designing with Plant Communities, by John Diekelmann and Robert Schuster. These authors draw their examples from native plant communities found in the northeastern quadrant of the US. They describe the main plant regions and how the plant communities function in them. In the back of the book are lists of native plants found in 13 types of communities ranging from boreal forests in the north to savannahs and dry prairies.

For even more detailed descriptions of natural habitats I would look to resources like Wetland, Woodland, Wildland. A Guide to the Natural Communities of Vermont, by Elizabeth Thompson and Eric Sorenson. This book describes the features and major plant species encountered in over 80 natural communities found in Vermont. Similar information can be found for states or regions in books or on websites. Some of those are listed at the end.

Plant Native, an organization based in Portland, OR, is dedicated to using native plants in a more natural way. They offer some excellent guidance on their website along with region-specific plant lists. One particularly useful bit, taken directly from their site, is to realize that …
“…in some instances, human development alters the characteristics of a site such that it may be advisable to use plants from a neighboring region. For example, plantings in urban and suburban areas may receive reflected heat from streets, sidewalks and/or walls or be in media that receives less moisture than normal (e.g., next to a paved area – the pavement blocks rain from entering soil). Accordingly, using plants from a neighboring region that support higher temperatures and/or drier conditions may be more appropriate” (See

Once you have a handle on the area you are working with you need to select the plants to fill the appropriate layers: ground covers, herbaceous perennials and grasses, woody shrubs, small and/or large trees. A typical foundation planting might be modeled on a forest edge or savannah community. Larger or more rural properties may have opportunities to use forest or prairie communities.

An example of a front yard planting modeled on a savannah would consist of some scattered trees like oak or pine under-planted with some shade tolerant perennials and shrubs. Open area would be planted with species preferring full sun. It is important that all the ground spaces be filled to block out weedy intruders.
While you can put together a plant community based on books and websites, there is nothing better than visiting natural sites and seeing some different plant communities. Visiting nearby sites also gives an idea of the native plants that work in your area. Many of the books and websites sited reference examples of places to go to experience these communities first hand (Diekelmann and Schuster’s book lists sites throughout the Northeast US).  Many botanic gardens have examples of native plant communities - and these have labels!  Garden in the Woods, in Framingham, MA and The Lady Bird Johnson Wildflower Center, in Austin, TX, are two of my favorites.

Additional Resources:
Plant Communities of New Jersey, by Beryl Collins and Karl Anderson

Natural Communities of Rhode Island

Classification of Massachusetts Natural Communities

Plant Native Website

Larry Weaner Landscape Associates  Larry Weaner has given some some great talks about work using plant communities.  Check out the website to see where he will be making future presentations.

Monday, February 15, 2010

Seeds that I am starting this Year

I just finished ordering too many seeds for me to handle this year, but I will give them all a shot. Most of these are native annuals or biennials and many are native to Massachusetts, where I am located. I thought I would share my list with you all.

Native to Massachusetts:
Adlumia fungosa (Alleghany vine, biennial, shown above), Aureolaria pedicularia (Fernleaf yellow false foxglove, annual), Bidens coronata (Crowned beggar’s ticks, annual), Corydalis sempervirens (Rock harlequin) , Hedeoma pulegiodes (American pennyroyal, annual), Hypoxis hirsuta (Eastern yellow star grass, perennial), Polygala sanguinia (Purple milkwort, annual), Pseudognaphalium obtusifolium (Sweet everlasting, annual).

Some of these plants will be tricky to start and use. As ‘wild’ plants they are adapted to thrive in specific environments. I hope to learn more about their requirements and how well they adapt to a residential garden. For example, Aureolaria pedicularia is parasitic on oaks and possibly ericaceous species; the Corydalis, Polygala and Pseudognaphalium are found on thin or depleted soils and may not do well in the relatively enriched soils found in most gardens. I’ve had good success with the Adlumia – these are seeds from a previous year’s plants.

Native to New England:
In addition to the seeds above I am trying these that are native to other parts of New England:  Monarda punctata (spotted bee balm, biennial; photo on left taken at Mount Auburn Cemetery wildflower meadow) and Rudbeckia triloba (brown-eyed Susan, biennial).

This Rudbeckia grows more as a bush with smaller, 'softer'-looking flowers than the more common Black-eyed Susan (R. hirta).

Native to other parts of North America:
Agastache aurantiaca ‘Navaho Sunset’, photo to right (Golden hyssop, perennial), Cleome serrulata (Rocky Mountain Bee Plant, annual), Eschscholzia californica (California poppy, annual/tender perennial), Euphorbia marginata ‘Summer Icicle’ (Snow-on-the-Mountain, annual), Gallardia pulchella (Annual blanket flower, annual), Phacelia tanacetifolia (Lacy phacelia, annual), Phlox drummundii (Drummond phlox – straight species, annual), and Salvia coccinea (Texas sage, annual/tender perennial).

I got the Phlox and Gaillardia on a visit to the Johnson Wildflower Center in Austin, TX.  (Well worth a visit whenever you are in that part of the country!)  These southwestern and western native plants are more decorative and may have a place in a home garden. They would be out of place in a meadow planting in the Northeast (or anywhere outside of their native ranges).

Wednesday, February 10, 2010

Selection of Regionally Native Plant Species

If you want to get really thorough about creating habitats for native wildlife, the plants you choose should be native to your area. In addition they need to be appropriate to the habitat you are working with, such as uplands, woodlands, wetlands, etc. There are two major challenges here. The first is to learn the plants that are native to your area, and the second is to find a source for the actual plant materials. Collecting plants from the wild is not an accepted (or legal) practice in all but a few rare cases. (Check this link to NEWFS for more details on plant collection.)

A few years ago I was fortunate to be given a copy of The Vascular Flora of Massachusetts, A County Checklist by Bruce Sorrie and Paul Somers . This provides a listing of wild-growing plants in Massachusetts, their status as native or introduced, and in which counties they are found. It is a rather technical source, but is a great help in developing a native plant palette. Other states have similar listings of native flora. The Flora of North America (FNA), available on-line, includes regional occurrence and habitat information along with the species descriptions. This is a work in progress; information on just over half of the plant families has been published so far. Gleason and Cronquist, The Manual of Vascular Plants of Northeastern United States and Adjacent Canada gives this type of information in book form. One book I have found very useful for learning about plants for a given habitat for New England is Wetland, Woodland, Wildland. A Guide to the Natural Communities of Vermont by Elizabeth Thompson and Eric Sorenson. The USDA-GRIN taxonomic database lists native ranges to the state level for many native plants. You can also do searches on the USDA Plants database by state(s) to find lists of plants growing ‘wild’ (use the advanced search options). A website with a good lists of native plants for use in residential landscapes, including northern New England comes from ‘Plant Native’. There is also a reference section there listing resources appropriate to other parts of North America.

Armed with this information you can check out what native plant suppliers have available. Finding suppliers close to home can be of benefit if the plant materials they are propagating from are drawn from local sources, or at least from similar climates. A similar situation exists for seed. It would not hurt to ask your seed suppliers where their seed comes from. It is my understanding that much of the commercially available seed for native plants comes from Ernst Conservation Seeds, based in Pennsylvania. There are also many regional seed companies operating in the Midwestern and Southwestern US supplying regionally native seeds. I have found that the options for regionally native seed suppliers in the Northeast is more limited. If anyone has any recommendations for suppiers in the Northeastern US, I would appreciate hearing from you!

The real strength of using native plants comes when you use them in complete communities. I will explore some resources and concepts for assembling a native plant community in an upcoming blog.

Monday, February 1, 2010

Spring Blue-Eyed Mary, Collinsia verna

If any one plant got me interested in native annuals, Spring Blue-Eyed Mary, Collinsia verna, was it. I saw photographs on the internet of this plant blanketing the understory of a woodland scene in spring and it made me think of siberian squill.  But this plant was native to the US!!!  Its native range is in the north-central US (New York to Virginia and west to Kansas).

This plant has an unusual life cycle that can make it a little tricky to grow in a residential landscape.  It is a winter annual, meaning that the seeds germinate in the fall and that blooming occurs in the winter or early spring.  The seeds need to go through a period of warm stratification for a couple of months and then they germinate as the temperature begins to drop.  The seedlings sprout as the leaves are falling, between September and October, taking advantage of the sunlight that is now available. It forms a small, few-leaved rosette that overwinters. In the spring, the seedlings begin to grow before the trees leaf out, much like woodland spring ephemerals, reaching a height of 8-12 inches. Bloom time is from early April through May. The widely flaring bell shaped flowers have 2 white petals at the top and two bright blue at the bottom. The ½-inch wide flowers are borne in whorls of 4-6. The seed ripens and is released in June and remains dormant in the soil until the fall. Collinsia verna is found growing in rich moist woods and alluvial soil from southern Ontario to Tennessee and west to Kansas. Populations are declining and it becoming rare at the edges of it range.
What makes this plant tricky to grow is that it is coming up when gardeners are busy raking leaves and ripping out spent annuals and perennial stems.  One must be careful not to trample or weed out these new seedlings.  Also these plants prefer a shaded, moist site.  I had some in full sun and they were cooked after a couple of days of warm spring weather. 

Seed for C. verna is of limited availability. I was fortunate to get some in 2008, but it has since been discontinued by that supplier. Seed is best sown fresh in place in early summer.  I planted seeds in a variety of places and saw germination in October only under a Crabapple tree in an area that had fairly consistent moisture and abundant sun during the growth period in the fall. I have also found some plants coming up and maturing in the spring after spending the winter in the ground. Fortunately C. verna is known to self pollinate, so that even if only a few plants are successful, I may get viable seed for the next season.  If anyone knows of a supplier of these seeds, I would love to get a hold of some more.

Other species of US native annual Collinsia, hailing from the western states, are C. grandiflora (Blue Lips) and C. heterophylla (Chinese Houses).  Seeds for these plants are more easily obtained.