In this column, the fourth in a series on functional native shrubs for the garden, I describe two shrubs well suited to wet areas of the garden, rhodora and speckled alder, and two shrubs for the more mesic sites, witchhazel and bayberry. While the later two species are part of our garden, we do not have a seasonally-flooded site to accommodate the needs of rhodora or the alder, although we do have visual ownership of the later as it grows along the drainage ditches that border the lane from our garden to the nearest highway. To enjoy the early May beauty of rhodora in bloom, we must travel the side roads that run through local bogs, or visit a local rain garden where runoff from a roof creates suitable habitat for this species.
Rhodora (Rhododendron canadense)
Native range: New England, NY, PA, NJ, DE
by Ralph Waldo Emerson
On being asked, whence is the flower?
In May, when sea-winds pierced our solitudes,
I found the fresh Rhodora in the woods,
spreading its leafless blooms in a damp nook,
to please the desert and the sluggish brook.
The purple petals, fallen in the pool,
Made the black water with their beauty gay;
Here might the red-bird come his plumes to cool,
And court the flower that cheapens his array.
Rhodora! If the sages ask thee why
this charm is wasted on the earth and sky,
tell them, dear, that if eyes were made for seeing,
Then Beauty is its own excuse for being:
Why thou wert there, O rival of the rose!
I never thought to ask, I never knew:
But, in my simple ignorance, suppose
the self-same Power that brought me there brought you.
Rhodora (Rhododendron canadense) is New England’s native rhododendron, a plant for all seasons. It is deciduous, flowering in late May or early June on leafless stems, the purple flowers often sharing space with last year’s orange-brown woody seed pods. After the flowers fade, we enjoy the blue green foliage of rhodora through the summer, particularly as new rosy-tipped seed pods develop among the leaves. On winter woodland walks, we look for the persistent seed pods at the branch tips, finding them dusted with new snow.
Rhodora forms dense colonies of four-feet-tall shrubs in lowland woods, often in seasonally flooded soils. In the swales between granite outcrops, where moisture is more limited, it grows to half that height. Wherever you find rhodora in bloom, look for bumble bees sipping nectar from the open flowers, and if you venture into a local spruce bog during the last two weeks of May, look for the reclusive bog elfin butterfly (Callophrys lanoraieensis) refueling on rhodora nectar. Energy restored, the small butterfly returns to the top of a black spruce tree where it lays its eggs on fresh needles. The first stage caterpillars bore into the spruce needles and feed from within, while the older caterpillars eat the needles from the outside. In addition to the bog elfin, several moth species also use R. canadense as a larval host.
Lucky indeed is the gardener with a pond or seasonally-flooded area where rhodora can herald the spring.
Speckled Alder (Alnus incana ssp. rugosa)
Native range: New England south to NJ, DE, MD, VA, and WV; west to NY, PA, OH, IN, IL, MI, WI, MN, and ND
A prime example of the subtle beauty of native shrubs is the speckled alder, Alnus incana ssp. rugosa, named for the white, warty lenticels on its bark. A large understory shrub (20 to 35 feet tall and wide) with a rounded crown and multiple crooked and leggy trunks, it can be found growing in colonies along the banks of streams and ponds, in low wet openings in the woods, in swamps and bogs. And this is where it should be grown in gardens, naturalized in wet areas with red maple (Acer rubrum), buttonbush (Cephalanthus occidentalis), willows (Salix sp.), winterberry (Ilex verticillata), mountain holly (I. mucronata), nannyberry viburnum (Viburnum lentago), and gray birch (Betula populifolia). While extremely tolerant of flooding, it is intolerant of shade and should be planted in open areas.
Speckled alder is an aggressive colonizing wetland shrub without brilliant spring or summer flowers, without showy fruit or handsome fall foliage. But I love to see this plant in winter, the drooping, purple-brown, snow-capped male catkins, the previous year’s small, woody, cone-like female catkins, and the coming season’s smaller red female catkins, all on the same winter twigs.
Alders are important members of wetland ecosystems. Before they turn woody, the female catkins produce tiny winged nuts that are a favorite food of redpolls, black-capped chickadees, pine siskins, goldfinches, waterfowl, small mammals and deer. Alder branches offer nesting sites for yellow-bellied flycatchers, alder flycatchers, yellow warblers, common yellowthroats, Wilson’s warblers, red-winged blackbirds, swamp sparrows, white-throated sparrows, and goldfinches. Alders are also host to several species of butterflies and moths, including the green comma butterfly (Polygonia faunus). And alders are nitrogen-fixing plants capable of adding up to five grams of nitrogen per square meter of topsoil per year. Their roots anchor the soil and prevent bank erosion.
Northern Bayberry (Myrica pensylvanica)
Native range: New England states and NY, PA, OH, NJ, MD, DE, NC, VA
Across its native range, northern bayberry forms immense rounded colonies in the wild, including coastal regions within the reach of salt spray. In gardens it flourishes in poor sandy soils where few other plants will grow. For sure, it is the native shrub of choice for stressful sites.
In Marjorie’s Garden, on a warm July afternoon, I cannot pass by the bayberries without crushing a leaf between my fingers and savoring the spicy scent. This is why we planted them, and for their bold texture and dark green foliage, and for the waxy, bayberry-scented berries that cluster along the stems of female plants.
And for their wildlife value. The fruits are important food for yellow-rumpled warblers, chickadees, red-bellied woodpeckers, tree swallows, catbirds, and bluebirds, while bayberry thickets provide nesting sites for songbirds, offering protection from raccoons and other nest predators. M. pensylvanica is a larval host plant for several moth species, including the Clemen’s sphinx moth (Sphinx luscitiosa), a species listed as threatened throughout its range, and the beautiful Io moth (Automeris io).
Witchhazel (Hamamelis virginiana)
Native range: Eastern U.S. states to the Mississippi River; also LA, TX, OK, AR, MO, IA, MN
In October, while most of Marjorie’s garden approaches dormancy, the common witchhazel (Hamamelis virginiana) is in full bloom. Where a few bright yellow leaves still hold fast to zigzag twigs, the flowers are hidden, but on naked twigs you can easily find the pale greenish gold and slightly fragrant flowers. They are clustered in threes along the stem where leaves were once attached, each flower bearing four twisted and crinkled ribbon-shaped petals. When temperatures are below freezing, the petals roll into tight curled balls, extending the life of the flower to ensure pollination when the temperature rises.
Common witchhazel is a small, often multi-trunked tree growing to no more than 20 feet in height; over much of its native range it grows as a large understory shrub both in the wild and in cultivation. Inconspicuous in the summer garden, it steals the show on blue-sky October mornings as its golden leaves reflect the angled sunlight. The flower display begins as the leaves start to turn and continues after they fall; in some years the flowers last until December.
The fruits of witch hazels, fuzzy two-beaked woody capsules, take a full year to ripen before exploding violently, each ejecting two shiny, hard, black seeds more than 30 feet away from the parent plant. After expelling their seed, the open capsules remain on the plant for yet another year.
In the wilds surrounding our garden, common witchhazel is often found growing beneath the shade of beech and birch trees, keeping company with beaked filbert (Corylus cornuta) and an occasional native honeysuckle (Lonicera canadensis), and surrounded by colonies of maple-leaf viburnum (Viburnum acerifolium). It frequents the drier sites, being intolerant of flooding. In the garden, use it along the edge of the dry woods or at the back of the garden border, placed where the October flowers will invite you to linger in the garden at a time of year when few other flowers beckon.
H. virginiana is a larval host for numerous moth species, including many of the tussock moths that frequent our garden and the seldom seen paddled dagger moth (Acronicta funeralis). And what insect, you might ask, goes about the business of pollination in October? Observed pollinators include fungus gnats, small parasitoid wasps, hover flies, and tachinid flies.