Sweet Fern is a small native shrub, densely branching, growing from 2 to 4 feet high on smooth reddish-brown stems that are erect and spreading.
Twigs are gray-brown and fuzzy and have resinous dotted hair.
The leaves are alternate and linear - 2 to 4 inches long but only up to 1/2 inch wide and have irregular teeth, creating 20 or more rounded lobes, so that they somewhat resemble ferns. The leaves are also dotted with glands and are fragrant when crushed, thus completing the common name of "sweet fern". There are a pair of small stipules at the base of the leaf that are semi-heart shaped. Fall color can be a nice reddish before turning brown.
The flowers are monoecious - that is, flowers separated by sex but on the same plant (although some plants are known to have only one sex). The male flowers (staminate) are elongated catkins, yellow-green in color initially, becoming reddish-green in flowering stage then turning reddish brown after flowering. These appear in clusters at the end of last years twigs. The color is provided by bracts which obscure the stamens. Female flowers (pistillate) are short rounded catkins that have reddish bracts obscuring the sexual parts, and after fertilization the bracts become yellow-green and appear bur-like when they extend into long narrow fingers, longer than the fruit when mature. The female catkins are further back on the twig behind the male catkins.
Seed: Flowers are wind pollinated. The fertilized flowers produce a round cluster of ovoid brown 1/4 inch long shiny nutlets in August, which mature in September and October. The average number of nutlets per fertilized catkin is 5.5 + or - .43 (Hall, Aalders & Everett - 1976). Seeds require breaking of dormancy to germinate and usually remain in the soil for some time and they are known to be viable for up to 70 years when they remain in the soil.
Habitat: Sweet Fern grows and spreads by rhizomes, forming colonies and is thus, good as a ground cover and bank stabilizer. It prefers poor to rocky soils, acid soils over limestone soils, in full sun, mesic to dry conditions. In Minnesota it tolerates partial shade but gets leggy. Sweet Fern is nitrogen fixing. It is difficult to propagate from seed, root cutting being the best way. Sweet fern appears in coniferous forest openings or woodlot edges. It is often the first species to appear on burned-over areas. The grey hairstreak butterfly (Strymon melinus) is restricted to feeding on sweet fern in the northern limits of its range. It is also used as a food plant by the larvae of some Lepidoptera species.
Names: The genus name Comptonia, is an honorary named by Linnaeus for the Rev. Henry Compton, 1632-1713, Bishop of Oxford. The species name peregrina is from the Latin and means 'exotic' and sometimes 'immigrant' and also 'foreign' but the modern definition of the word is 'female pilgrim', all of which makes it somewhat difficult to conclude what the author had in mind in picking that name. The older scientific name for the species is Myrica asplenifolia, where the species name meant 'with leaves like a fern' which indeed was easily to understand. The author names for the plant classification are: First to classify was (L.) which refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy. His work was amended by ‘J.M.Coult.’ which is for John Merle Coulter (1851-1928), American botanist and head of the Botany Dept. at the University of Chicago.
Above: When in full sun, Sweet Fern is an upright plant, otherwise it may sprawl. 2nd photo - The pair of semi-heart-shaped stipules at the base of the leaf. 3rd photo - The bracts of the female flowers extend into these bur-like fingers after fertilization of the flower.
Below: 1st photo - Male flowers are in elongated catkins at the end of twigs. 2nd photo - The female flowers are further back on the twig with reddish bracts obscuring the sexual parts.
Below: A twig with both male and female catkins showing
Below: 1st photo - The aging male catkin after pollination. 2nd photo - The extended bracts of the female flowers with the fruit forming. 3rd photo - The smooth shiny ovoid brown nutlets formed in the bur-like cluster of the female flower in late summer.
Below: The long narrow leaves with rounded lobes are irregularly toothed and fragrant, and resembling a fern, from which comes the common name.
Below: Leaves of Sweet Fern leaves provide interesting fall color
Notes: Eloise Butler's first notation on planting Sweet Fern was on Sept. 4th, 1909 with plants obtained from Stony Brook, Ma. Martha Crone reported planting it on July 31, 1933 (4 plants from Duluth), on Aug. 17, 1933 (7 plants from Hinkley) and on July 30, 1934 (12 plants from Duluth) and noted planting them in a sandy site. More plants in 1945 and 1948.The older scientific name used at the time was Myrica asplenifolia. On her 1951 inventory she listed it under another older family name - the Wax Myrtle family.
Sweet Fern is native and it's range is entirely east of the Mississippi with Minnesota the western-most state. In Minnesota Sweet Fern is found only in the NE Quadrant, hence the Garden population this far south is somewhat unique, but it grows well in the Upland Garden although it rarely gets to 2 feet high there. It is the only species of Comptonia found in North America.
Concerns: Sweet Fern is a host of the Sweet Fern Blister Rust (Cronartium comptoniae) which affects the Jack Pine (Pinus banksiana). Jack Pine is a common pine in the areas of Minnesota where Sweet Fern is native.
Eloise Butler wrote: "We nibbled quantities of the nutlets of Sweet Fern, Myrica asplenifolia. Boys made cigarettes of the leaves. It wasn’t fashionable in our set for girls to smoke. I have failed to induce this plant to grow, although I try every season." From Children’s Forage Plants in the Wild Garden, January 1915, unpublished.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"