Rhodora Rhododendron canadense Ericaceae
Wild Seed Project: Returning native plants to the Maine landscape
June 2016

Early-flowering, colonizing shrub, three to four feet tall; normally found in cool, moist, peaty soils in sun or part-shade; striking magenta flowers appear before foliage; deer-resistant; creates, in multiples, good habitat for small birds; ranges from Newfoundland west to Ontario and south along the eastern seaboard to Pennsylvania and New Jersey.

By Pamela Johnson

April and early May possess singular moments hinting at the regeneration yet to come. In Maine we live in a landscape that can appear wintery for more than the calendar’s allotted three months- though meteorologically autumn increasingly jostles December, and spring nibbles winter’s conclusion in March, with each warmer year. The leaves depart with migrating birds; the landscape looks curtailed especially without snow to reveal the daily diacritics of mammalian activity.

Intimations of the landscape’s renewal arrive in cautious pulses of color. Most of us are alert for the first argent glints of pussy willows while missing the precious gold of pollen on garnet alder catkins, nutriment essential for the earliest active insects and hungry birds.

Then there is the poplars’ show. The trees’ outlines effervesce with bloom— catkins again, large, loosely assembled, like blowsy larvae, as if Edward Lear had drawn them and made a tree out of fuzzy caterpillars. The range of poplar catkin hues is is surprising: each tree’s upper branches a blur of yellows, silvery green, olive, or puce.

The red maples next claim the stage with small puffs of orange (male or staminate flowers) and crimson (female, pistillate flowers). It is the aggregate of thousands of blossoms on a single tree that has such eloquence, and poignancy when the blooms fall to the ground, still sanguine, as if carnage had just been done.

The Amelanchiers march along next in small, exquisite cadres, especially Amelanchier laevis, smooth shadbush, whose buds and flowers are set off by the fulvous embrace of young leaves. Shadbushes have long been Spring’s timekeepers. John Eastman writes:

Few plants have provided such a widely used seasonal clock as shadbushes, a function reflected in many of their common names. On the eastern seaboard, colonial fisherman timed the spawning runs of shad fish by the flowering of this plant Shadbush flowering also marked the time of burial services for colonists who had died during the winter, hence serviceberry.[i]

There are, of course, other early emergences, single tokens of green precociousness like that of American honeysuckle, Lonicera canadensis– beautiful, and unusual in that its leaves and flowers coincide, requiring approximately the same length of winter cold to break dormancy. (The flowerbuds of most of our woodland trees and shrubs need fewer cold days to open than their leaf buds.) Sambucus racemosa, red elderberry, swells its fat, purple buds early; hobblebush (Viburnum lantanoides) often begins its tawny resurrection in squalls of wet snow and sleet. And usually we only notice skunk cabbages (Symplocarpus foetidus) when they course deep green through still-slumbering thickets.

The last broad brushstrokes of color, before late May’s full spate of flowers and foliage, belongs to rhodora, Rhododendron canadense. Its blooms appear in magenta undulations flowing in and around the bare gray stems of common winterberry (Ilex verticillata) and the winter-tattered, and not yet revived sheep American-laurel (Kalmia angustifolia ssp. angustifolia) two of its habitual neighbors. The color is sensational in a landscape that has barely shrugged off the cold: magenta, pink, violet— unexpected shades for a shrub that flourishes in northern New England, and often in its coolest, dampest habitats.

Rhodora’s beauty comes from its unique, early color and from the graceful informality of its flowers whose buds are poised at the ends of the shrub’s upright stems, and open in advance of the leaves. Emily Dickinson wrote in 1858, “Frequently the woods are pink/ Frequently are brown”.[ii] Reverse the couplet and you hear the simplest description of rhodora’s reawakening, and transformation of its habitat.

Dickinson included a specimen of rhodora in her schoolgirl Herbarium. “Rhodora canadensis” shares a page with a hulking splay of sweet bay magnolia (Magnolia virginiana), labelled “Magnolia, glauca” and a fecund hank of sheep sorrel (Rumex acetosella). Her care with the mounting has preserved many of the protruding flower stamens and shows the near-transparent delicacy of the flower petals, faded to incarnadine.

The poet was not interested in the phenological record when she created her Herbarium; there is no data attached for collection site or date, just the plant’s Latin binomials written carefully on the strip of paper which affixes each plant’s stem to its page. Dickinson used the former name for rhodora, Rhodora canadensis. For some time rhodora was isolated in its own genus[iii], exiled by its distinctive corolla (the flower petals, collectively).

Rhodora’s flowers are zygomorphic, meaning they are bilaterally, not radially, symmetrical (actinomorphic). The corolla’s upper petal has three shallow lobes; the two lower petals have no lobes. Rhodora’s petals are barely joined at the base- they look ready to disassemble themselves just as they bloom, though the flowers are actually quite persistent. The tube that ought to join the petals is almost absent, whereas rhododendrons commonly have tubular or trumpet-shaped corollas.

Peter Loewer in Jefferson’s Garden briefly relates a tale about Sir George Sitwell (1860-1943) who created an Italian Renaissance garden at Renishaw Hall in Derbyshire, England. Sitwell loved plants, but not necessarily their flowers, and he found the effusive blooms of rhododendrons so especially distasteful that he had them removed. Another version of the story is that Sitwell’s son Osbert meticulously deadheaded the rhododendrons to produce even more of the flowers that so vexed his father. One wonders if Sir George would have objected to rhodora’s delicate, gauzy inflorescences.

The sexual parts of rhodora blossoms are robust— stigmas, styles and stamens extend beyond the petals’ circumference; they look like the long, rosy legs of a foraging insect, perhaps something wasp-like, protruding and a little minatory when stirred by a breeze. Thomas Wentworth Higginson writes in Our Northern Shrubs (1925):

On the margin of some quiet swamp a myriad of bare twigs seem suddenly overspread with purple butterflies…there is nothing else in which the change from nakedness to beauty is so sudden and [later] they appear ready to flutter away again…and leave you disenchanted.

There is nectar to be found in the flower’s base, enough to attract early pollinators and other insects. Some of the candidates for melittophily include the sweat bees (Lasioglossum species); bumblebees (Bombus bimaculatus, B. fervidus, B. ternarius) and flower flies (Eristalis anthophorinus) members of the Diptera family.

One of rhodora’s most unusual faunal associates belongs to a habitat more specialized than where the shrub is commonly found. Rhodora happily colonizes the sloughs of roadside ditches, its underground stems nicely buried, and protected, by annual layers of plowed road-shoulder grit. The shrub can also take hold among glades of mountain holly (Ilex verticillata), snarled with sheep American-laurel (Kalmia angustifolia ssp. angustifolia) in ledges that manage to retain both moisture and a thin layer of acidic soil.

It is in the fens and bogs where rhodora mingles with black spruce (Picea mariana) that one finds the bog elfin butterfly (Callophrys lanoraieensis). Adult butterflies sip rhodora’s nectar, and their larvae feed exclusively on black spruce needles — one instar munches from within the spruce needles; the second instar eats its way to the needle surface. In the closed ecosystem of a true peat bog— highly acidic, saturated, oxygen- and nutrient-poor— only two trees and a handful of shrubs, forbs and sedges can survive. Black spruce and American larch (Larix laricina) are the diagnostic trees; black spruce may be years old and only foot-high due to the extremity of the habitat. Rhodora will flirt with the edge of such a bog, but requires the safety of drainage, and the replenishment of organic matter. The nearby coolness of a bog, with its own microclimate, suits rhodora very well.

When the blossoms do evanesce in June, rhodora’s soft green foliage is a restful backdrop for swamp rose (Rosa palustris) and shining rose (Rosa nitida). Rhodora’s leaves are described as blue-green or gray-green, and seem not to be of interest to foraging mammals perhaps because they are slightly downy, a mealy mouthful for deer. (Rhodora’s nectar, like that of the entire family, contains some acetylandromedol. Honey gleaned from Mediterranean rhododendron species was called “mad honey” for its unfortunate effects.)

Rhodora’s perky seed capsules perch at the shrub’s branching tips, conveniently located to split open in the cold and, with a rattle of icy wind, spill their contents onto the ground.

As members of the Ericaceae, the heath family, rhodoras benefit from the lean, acid soils naturally found in Maine. Bill Cullina notes in Native Trees, Shrubs and Vines that overly fertile soil reduces the mycorrhizal fungi essential to ericaceous plants. While rhodora is so exquisitely in bloom, in the wild, take the opportunity to notice where the shrubs grow with abandon.

 

Rhodora seed capsules take the full growing season to ripen, changing from green to tannish brown, and splitting in mid-autumn. Like all rhododendrons, the seeds do not need a winter cold-period to germinate. Most propagators sow the seeds in the winter, indoors under lights or in a greenhouse. Seeds are sown on the surface in a soil mix of sifted sphagnum peat moss, then covered with plastic to maintain moisture until germination. Seedlings are slow growing and may reach a few inches in height by springtime. Juvenile plants can be moved outdoors in late spring or early summer. In the wild, seeds of rhodora often germinate in a bed of moss or on a rotten log. This can be mimicked in a nursery environment, and, though it is a much slower method, does result in robust plants.


[i] John Eastman, Forest and Thicket, 1992. p. 177.
[ii] Emily Dickinson, The Complete Poems of Emily Dickinson, ed. Thomas Johnson. 1960. p.8.
[iii] This ignores the taxonomic interval when rhodora and the other deciduous rhododendrons including some of New England’s loveliest species, were banished to the genus Azalea (Azalea canadensis for rhodora) to distinguish them from the evergreen rhododendrons.