Biennial Gaura is a native erect annual to biennial forb, producing a basal rosette the first year and then sending up 2 to 5 foot stout hairy branching stems in the second year. Stem hair is whitish, long and spreading. These stems are green when young and become reddish, hard and woody when mature causing difficulty with harvesting equipment when the plant appears in a crop field.
Leaves: The stem leaves are alternate on stem, stalkless, lance shaped, pointed at both ends, 2 to 4 inches long and half as wide. The edges are usually wavy but may have some sparse teeth. The upper surface is smooth, the underside with hair. Leaves, particularly the edges, pick up a reddish tint toward late summer.
The inflorescence is an elongated branched spike, or panicle, that occurs on the terminal ends of the stems. Flowers are stalkless and open at the bottom of the spike first, with a clump of hairy pinkish buds above.
Flowers: Individual flowers are 1/2 to 1-1/4 inches wide, 4-parted; the corolla has 4 white petals, elliptical in shape with a narrowed base. Petals spread outward and slightly backward and appear only on the top side of the reddish corolla tube and then turn pinkish when they wither. The calyx tube is long with 4 pointed lobes which reflex when the flower opens. The flowers are perfect with, usually, 8 stamens that have long white filaments and pale yellowish anthers which mature to a much darker color. The stamens are separated on either side of long style that has a 4-parted stigma. The one-celled ovary is at the deep base of the calyx tube. All reproductive parts appear to be slightly drooping compared to the upright petals.
Seed: Fertile flowers produce a nut-like seed that has 4 ribs, pointed at both ends, downy and up to 1/2 inch long.
Habitat: Gaura establishes itself from seed and produces a fibrous root system. It is quite adaptable, accepting most soils, moist to dry conditions but it does need full sun. If a patch needs control simple cut out the autumn rosettes or de-stem the plant at flowering time.
Names: The genus Gaura (pronounced 'gaw-ra' by English speakers and gār-ra by Spanish speakers) is derived from the Greek gauros, meaning 'superb' and referencing the showy flowers. The species name biennis simple refers to a 'biennial' plant. The author name for the plant classification - 'L.' is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy. There is debate in the scientific community as to whether the species should remain in the genus Garua or be classified as Oenothera gaura W.L.Wagner & Hoch, as USDA has done. Minnesota authorities at the U of M and the DNR have not made that change.
Comparisons: The only other Gaura species found in Minnesota that looks something like this species is Scarlet Gaura, G. coccinea, but there the the petals are reddish pink to white, the stems are green and the plant is a perennial.
Above: The inflorescence is tall and leafless. Drawing from Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York.
Below: 1st photo - The 4 white petals are all on the upper side of the flower, which droops. Petal bases are very narrowed. 2nd photo - The buds and calyx tube are narrow, long and pinkish in color. Note the divergence of the stamens around the style.
Below: 1st photo - Leaves are pointed at both ends, with wavy edges and some with a few teeth and reddish tints. 2nd photo - the underside has fine hair on the surface and ribs.
Below: 1st photo - The inflorescence is an elongated panicle. Except for the first year basal rosette, leaves are on the stem only. 2nd & 3rd photos - The panicle stalk, flower stalks and the calyx all have fine hair, as does the stem, which becomes hard and reddish at maturity.
Below: Seeds are downy with 4 ribs, up to 1/2 inch long. Photo courtesy Jose Hernandez, USDA-NRCS Plants Database
Notes: Biennial Gaura is relatively new arrival in the Upland Garden after a long absence. It is not indigenous but was originally planted in the Garden by Eloise Butler on Oct. 14, 1930 with plants from Delphi Indiana. Two species of Gaura are found in Minnesota, the current species and G. coccinea, Scarlet Gaura (Scarlet Beeblossom). A third - G. mollis, Velvetweed, has been reported but never collected and the DNR does not even list it on their species list. G. coccinea is more widespread; G. biennis has only been collected in Hennepin, Ramsey and Houston counties and is listed on the DNR 'watch list'. In North America it is a plant of the eastern half, east of the Mississippi River excepting Florida and New England. In Canada it is known in Ontario and Quebec.
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"