Salt may limit viable choices for roadside plantings

Gardening season is upon us. The peas and onions are planted in Marjorie’s garden, the raspberries and blueberries are awake, and gardening questions seem to be propagating in the inbox.

Leigh McCarthy e-mailed this question: “I am seeking your advice as to what to plant for a mixed shrub/tree row that would serve two purposes: (1) screen a Hancock County house from a busy road and (2) provide bird habitat and food. Whatever I plant must be winter hardy, salt resistant, and as deer resistant as possible. It should screen from the ground up to perhaps 20 feet or so. I am considering a mixture of pagoda dogwood, elderberry, rugosa roses, bird cherry and black cherry. Am I off-track? Would you recommend any other components?”

First let’s get the rugosa roses off the list. Rosa rugosa is a non-native invasive species that is displacing native rose species in coastal areas of Maine. I recommend that gardeners replace the rugosa rose with a native rose, Rosa carolina, whenever possible. It is a lovely alternative with large solitary flowers, deep pink in color and fragrant. The bright red hips are persistent and brighten the winter landscape.

I try to avoid adamant statements about deer resistance as they will eat almost anything when push comes to shove, as it did this winter in many areas of Maine. As to salt resistance, the rose I mention is considered sensitive to de-icing salt. Perhaps you can site it far enough from the road to avoid the salt spray that damages winter buds.

Both cherries meet all of your requirements, although both eventually exceed 20 feet in height. However, I am dubious about the pagoda dogwood’s tolerance for salt; it is not a tree that I would recommend for plantings exposed to salt spray.

You could try a mixture of both the red elder, Sambucus racemosa var. pubens, and the American elder, S. canadensis. I have always wanted to see these two native shrubs growing in the same garden, the bright red berries of the red elder ripening as the American elder is flowering. Again, however, their sensitivity to excessive salt could be a problem. Is there any area of the garden that will be less affected by the salt? Perhaps you could plant them there.

There are a few salt-resistant plants that I will suggest. Northern bayberry, Myrica pensylvanica, belongs in your garden, as it can handle the salt spray. It will grow to at least 6 feet in height and provide dense foliage as well as berries with high wildlife value.

Can your site handle a plant as exuberant as staghorn sumac, Rhus typhina? It is a great bird plant, if you plant a female, has beautiful fall foliage, and will grow to at least 20 feet high. It has a colonizing habit, however, and must be watched, each year removing the unwanted suckers.

Smaller salt-resistant shrubs with high wildlife value include black chokeberry, Aronia melanocarpa, to 6 feet in height; highbush blueberry, Vaccinium corymbosum, to 12 feet high; and wild raisin, Viburnum nudum var. cassinoides, to 12 feet. Do not overplant the wild raisin, however, as it is a favorite of the viburnum leaf beetle.

Salt-resistant small trees with high wildlife value include shadblow serviceberry or Amelanchier canadensis, gray birch or Betula populifolia, and pitch pine, Pinus rigida. The pine has greater wildlife value than many people realize, its seeds eaten by many species of songbirds. It also has a picturesque growth habit, recurving branches that grow twisted and gnarled, perfect for a coastal landscape.

Send queries to Gardening Questions, P.O. Box 418, Ellsworth 04605, or to rmanley@ptc-me.net. Include name, address and telephone number.