Garden Notes

Seaside goldenrod
Seaside goldenrod deserves a place in Island gardens, especially those with sandy soil and good drainage. Photo by Susan Safford

Allergic to goldenrod? Maybe not

By Abigail Higgins - October 11, 2007

Like the prophet with no honor in his own land, the Solidagos, the goldenrod tribe of the great Asteraceae nation, are routinely overlooked, or actively disparaged, in their native North American homeland. At the same time, European and British Isles gardeners spotlight goldenrod as a plant treasure, to be placed front and center in their late summer gardens.

Recently I met with a garden owner for whom I work, to discuss her ideas for planting a sloping hillside above a terrace with native plants that would look good and thrive there. It being late September I mentioned goldenrod - a great bank holder, forage for butterflies and pollinators, native plant supplying colorful end-of-season bloom, et cetera. Almost immediately she shook her head and explained that members of the family have allergies.

Sometimes, as we all know, one simply cannot contradict the person one works for. I wimped out. (Besides, everyone has plants that are disliked: goldenrod might be such a plant for this individual.) Yet, I felt remiss about not countering this latest repetition of the neighborhood myth that goldenrod is responsible for allergies; people are often quite certain they know what causes their misery. Thus, my belated goldenrod rebuttal became this week's Garden Notes instead.

Allergists, botanists, and environmentalists all have expended many papers and essays attempting to dispel the perception in the popular mind that goldenrod causes allergies. The main fact supporting this is that insects are the means of dispersal for the goldenrod pollen grains, which causes them to be heavy and sticky. (For wonderful images of the range of insects that visit goldenrod go to http://www.pollinator.com/goldenrod.htm.) Deplorably however, the season of the showy goldenrod coincides with that of the inconspicuous ragweed.

Ragweed the culprit?

Ragweed, drab and ubiquitous, on the other hand has pollen that is wind-dispersed, which method causes the pollen grains to be lightweight, airborne, and everywhere! Whatever I have managed to read about goldenrod and allergies reiterates over and over that it is ragweed (Ambrosia artemisifolia), not goldenrod, which is to blame for end-of-summer allergy misery. It is hard for a grain of goldenrod pollen to fall up into one's nose. Ragweed pollen blows; ragweed is the allergen in most cases.

Having emphatically dismissed the allergy misconception, let's take a look at the ornamental qualities of goldenrod, free of the fear of rhinitis and sinusitis. It is something of a hard sell here on Martha's Vineyard, in New England, or anywhere in North America, for that matter. Ragweed is not the only ubiquitous plant. Goldenrod is all around us, common as dirt, beside every Island lane and highway. Goldenrod lacks the luster and punch it acquires across the Atlantic, as if its familiarity debases its value.

Perhaps due to its very abundance, but more likely due to promiscuous hybridization, goldenrod species are notoriously difficult to identify. The "Flora of Martha's Vineyard" lists 27 species (including two which have now been assigned to Euthamia,) of which I might be able to pick out five or six. Allen Armitage in "Herbaceous Perennial Plants" (Stipes Publishing LLC, Champaign, IL 1997) cites five species and 13 hybrid cultivars.

The most distinctive Island species is the handsome seaside goldenrod, Solidago sempervirens (pictured above), which is familiar to most of us as it too is a beach-loving Islander. It is usually found at or near the beach, a strong-growing perennial with long, pointed, glabrous leaves, somewhat waxy, that form a large basal clump. Arising from this are strong-growing stems with discrete golden yellow composite flowers in a panicle at the end. Growth is often lax so plants can be between knee to waist height.

Working in shore gardens, we often let a seedling S. sempervirens grow into a garden feature when it occurs in an appropriate spot. Normal perennial bed soil may be better than it needs, causing it to suffer from rust, an unsightly orange dust-like smattering on the foliage; but that does not seem to affect the plant's overall hardiness. Stake it to contain sprawl, or cut back by half in June.

A resident goldenrod at our place is Euthamia tenuifolia, the slender-leaved goldenrod. Left to its own devices, this delicately textured plant forms large colonies, about two feet high, spreading, unlike the clump-forming S. sempervirens, by underground rhizomes. I find it lovely and would use it if a suitable naturalizing project came up. It is often seen in old meadows that are fairly fertile, and in bloom it is covered in pollen-guzzling insects. The single-veined foliage is slim and pointed, slightly reminiscent of a tarragon plant, with flat-topped corymbs made up of very small individual composite flowers.

According to the Connecticut Botanical Society's goldenrod web page by Arieh Tal, http://www.ct-botanical-society.org/docs/ solidago.html, there are only two New England Solidagos whose flowers occur in the leaf axils along the stem and S. caesia. Bridal wreath goldenrod, is one of them. Could it be another goldenrod I have seen near my house? Several aspects confound, however, as the stems are not blue: S. caesia's second common name is blue-stemmed goldenrod. The other goldenrod listed as axil-blooming, S. flexicaulis, has a zigzag stem while the Christiantown plant has straight stems. "Flora..." cites S. caesia as an inhabitant of mesic forests, sparse woods and borders, rare, native and as growing at six known [Island] sites.

Silverrod, or white goldenrod, is another plant cited in "Flora...." S. bicolor is described as "occasional, native." I have not personally seen this plant but it should be easy to identify if one were to: it is the only goldenrod with white flowers.

Resident goldenrod

Much of the goldenrod one sees on Martha's Vineyard appears to be either S. rugosa, the roughstem goldenrod or perhaps one of its sub-species, or S. canadensis, the tall goldenrod. One other family member that is listed as abundant on Martha's Vineyard by "Flora..." is S. odora, the sweet or licorice goldenrod. S. odora does not appear in the Connecticut Botanical web page table, so I was not able to cross-reference it there. However, the leaves have a scent similar to licorice when crushed and S. odora is the only goldenrod to possess the scent, so that makes an easily checked feature.

Among the hybrid goldenrod cultivars that Allen Armitage rates to look out for in "Herbaceous Perennials" are several forms that could be considered almost dwarves. Certainly, by summer's end, most of us are ready to eliminate staking any way we can, so these sound promising. (Otherwise, cutting most goldenrods back by half in June accomplishes stockier growth.)

The following are some of Armitage's comments: "'Cloth of Gold' is a dwarf but vigorous grower with dense, deep yellow flowers and grows 18-24 inches tall. 'Crown of Rays' ('Strahlenkrone') has to be one of the best goldenrods I have trailed.... The plants grow 2-3 feet tall without falling over, and are covered with bright yellow plumes of flowers in mid to late summer. 'Golden Thumb' grows about one foot tall with yellow flowers and yellowish green foliage. My choice as the most ornamental and useful dwarf form."

Goldenrod is an excellent cut flower and was, many years ago, grown extensively for this purpose. After being out of favor, it is once again becoming popular in the trade, its ease of arranging, good stems, and long vase life accounting for the reprise. On the minus side, goldenrod is prone to rusts and mildews. But so is a host of other popular garden plants: these problems can be dealt with. Think about adding some goldenrod to your Island garden.