Snowplows and Roadside Plantings, a Case for Native Annuals

Last week I did the spring clean-up of a roadside bed I designed. The plants used were all Eastern North American species.  As I was working I was reflecting on what did and did not work well. For the most part it has been doing quite well with little input from me. Up away from the main traffic flow Aronia (Aronia arbutifolia), Meadowsweet (Spiraea latifolia) and Shrubby Cinquefoil (Potentilla fruticosa) are growing well as are the perennials including Prairie Aster (Symphyotrichum turbinellum), Purple Coneflower (Echinacea purpurea), Appalachian Blazing Star (Liatris squarrulosa), Stiff Goldenrod (Solidago rigida), Red Columbine (Aquilega canadensis) and my favorite grass, Prairie Dropseed (Sporobolus heterolepis).



When I designed this roadside bed back in 2006, I selected plants that I thought would withstand drought conditions, salt spray, full sun and wind. The one aspect that I had not fully appreciated was tolerance to disturbance, particularly resistance to snow plows! Where the bed is protected by a curb there is not much of an issue, but down near the highway the surface of the bed is often scraped over, either directly by the plows or as a result of snow being pushed up and over the sidewalk.

    

When I first learned that blueberries were salt tolerant I happily incorporated them into the roadside position.  I thought people going by would be impressed at how versatile of a shrub blueberries were. I was shocked the following spring when I found the bushes pushed nearly a foot further into the bed, the result of plowing of the snow. Well, the plants are still there 4 years later, but just hanging by a thread. This is obviously the wrong place for what would otherwise be the right plant.



Problem area, after a fresh layer of leaf mulch. 
The blueberry twigs are still in there.



Down by the road Seaside Goldenrod, Solidago sempervirens, is performing well. In fact, this is an example of a native species that is expanding into the urban environment in disturbed areas where road salt makes it difficult for other species to establish. The Prairie Dropseed in this area (those that haven’t been plowed over) are not doing as well. However, Sand Love Grass, Eragrostis trichodes, a new addition to this area does seem to be doing better.

Considering the conditions at this end of the planting I really need a plant (or plants) that will have a continued presence despite a nearly annual scraping of the top layer of soil. Use of a native annual, or perennial, that vigorously self-seeds should fit the bill. Since the plant starts each year anew, disruption of the crown and roots would not be an issue.

This year I have seeded in some American Pennyroyal, Hedeoma pulegioides, a true annual that grows in dry disturbed locations and produces a lot of seed. I also added seeds for a couple of perennials, Spotted Beebalm, Monarda punctata, and Butterfly Weed, Asclepias tuberosa, that are known to reseed effectively and have some salt resistance. By starting from seed I am testing whether this site has the right conditions for germination, a critical factor if they are to get established there.

To get some new ideas I turned to the Advanced Search  function on the USDA Plants database. Here I looked for plants that will tolerate full-sun, drought and salt. While not every plant in the database is searchable in this way, it can provide many leads. Among the results was the Seaside Goldenrod that is already thriving there. A new lead that was generated was Beach Sunflower, Helianthus debilis. I’ve been growing this from seed in pots at home for a couple of years, now it’s time to put it to the test in the field!

Strawberry Blite, it's not a disease!

Despite it’s common name (formerly of the genus Blitum) Strawberry Blite, Chenopodium capitatum, also known as Beetroot and Strawberry Spinach, has some attractive features.  The small ball shaped flower clusters (up to ½ inch) start out green but shortly turn bright red. These flowers mature to bright red edible fruit clusters (to ¾ inch) that contribute to the plant’s common name. The leaves of this species, as with other members of the genus, can be eaten like spinach, fresh or cooked.

Since I was interested in seeing how the aesthetic value of this plant developed, I did not taste the leaves or roots, both of which are edible.  I did try the red berries on several occasions.  They were slightly sweet and not unpleasant, but the seeds were rather large and hard.




Nice leafy example of Strawberry Blite in good soil, late spring.

 This plant is in the same genus as naturalized species Lamb’s Quarters, C. album, and as such I expected it to be equally vigorous.  My experience with this plant has been mixed. I was able to get good germination of the seed under lights without any pretreatment, but I did have problems getting plants to develop after transplanting, in a variety of soils.  I had better results direct sowing the seeds.  The seed pack indicates that they should reach maturity in 40-60 days.  In my crowded New England garden it took nearly 2 months for the plant to reach good size.  It has an upright and branching form, 8-24 inches in height. The gray-green leaves are triangular (as much as 4 inches on the lower branches) and alternately disposed on the branches.  The overall appearance is somewhat coarse.

The wild distribution of C. capitatum is throughout the northern half of North America including Alaska and into the Southwest.  It is not usually found in the Southeast or lower Plains States.  It is listed as a native to Connecticut, but as an introduced species to Massachusetts.  The native habitat is in open woods and can also be found along roadsides. It is often observed reappearing after fires.  It is noted the Sierra Club Naturalist's Guide to Southern New England that the seeds are very long lived.  As with other members of the genus, it produces large amounts of seed.  This may be a consideration in the garden, for once established, it may be difficult to permanently eliminate this plant from the site.

Overwintered plant developing flowers at end of May.

While listed by many sources as annual, I found that it is actually monocarpic.  Well at least I did after I looked up what that means.  A monocarpic plant lives to produce a single crop of seeds then it dies. In my case a couple of clumps of this plant grew as a leafy mass after transplanting and then developed flowers and fruits the following year before passing on.  A monocarp is not necessarily short-lived.  For example, Black Bamboo, Phyllostachys nigra, is also monocarpic, but it may take 70 years before it reaches maturity to produce a crop of seed.  After that the plant will die a natural death.

The genus Chenopodium has high wildlife value.  It is a food source for many birds including the snow bunting, catbird and morning dove.  This species serves as a larval host for the common sootywing butterfly (Pholisora catullus).  In addition to its value as a food plant, the red berries have been used dyes by several Native American groups.

The seeds are available from B&T World Seeds and Horizon Herbs (my source).  While I would really like to use seeds from my own eco-region, the provenance of these seeds is not likely from this area seeing as one supplier is in Europe and the other in Oregon.

For me the jury is still out on this plant.  Since I let most of the berries go to seed, I will watch for its return and test the flavor of the roots and leaves this time.  As a garden plant, its habit was too lax to be a featured highlight, although it could work in the background.  Has anyone else had experience growing this plant?   Stay tuned.