Flower:

Densely flowered spikes, 4 to 8 inches long, multiple branching at tips of stems and branches, elongating with age, flowers blooming near the tip and fruit forming below. Flowers are initially white, turning pink especially as they wither, about ½ inch long and wide, with 4 broadly spoon to diamond-shaped petals, mostly erect and arranged fan-like on the upper half of the flower. In the center are 8 slender white stamens, about as long as the petals, tipped with slender yellow to reddish brown anthers, and arranged fan-like at nearly a right angle to the petals. The single style is also slender, longer than the stamens and has a pale, 4-parted tip.

The calyx at the base of the flower is tubular, short-hairy, the 4 sepal lobes narrowly oblong, about as long as the petals and longer than the tube, strongly bent downward with the edges tightly rolled inward, often reddish green. Resembling a stalk at the base of the calyx is the ovary, about as long as the calyx tube, slightly swollen in the middle, short-hairy and with distinct ribbing.

Leaves and stems:

First year leaves are in a dense, flat rosette, second year leaves are simple and alternate, narrowly lance-elliptic, tapered to a narrow base and pointed tip, 2 to 4½ inches long, up to about ½ inch wide, stalkless, with widely-spaced, shallow, gland-tipped teeth around the edges. Edges may be crinkly or wavy, especially when young. Surfaces are covered with scattered, short, appressed hairs, especially along major veins on the underside, upper leaves becoming nearly smooth.

Stems are multiple from base, erect to ascending, branching above, angled or round in cross-section, variably hairy, more densely covered in spreading white hairs on the lower stem with some glandular hairs especially towards the flower spikes. Both stems and leaves often develop tinges of red.

Fruit:

Fruit is diamond shaped, 4-sided with a large rib along each angle and a smaller rib on the surface between them, cone-shaped at the tip, ¼ to 1/3 inch long, with fine surface hairs.

Notes:

Biennial Gaura, formerly known as Gaura biennis, is a common species of eastern tall grass prairie, woodland openings and river banks. The four Minnesota collections would represent the extreme northwest extension of its range, two dating back to 1899 from Houston county and two more recent from metro Hennepin and Ramsey counties. While the DNR treats the species as native, this is more reasonably based on the earlier occurrences, the later two possibly human assisted, found in weedy areas along RR tracks. We recently encountered what is unlikely a natural population, widely scattered but near trail edges at a Ramsey County park, a single plant first spotted in 2014 and several more in 2015. Obviously never common, natural populations might well be considered historical in our state. Untidy but still an attractive species, even with numbers of inter-generic horticultural hybrids showing up in the gardening industry, the native wild form can be occasionally found in restoration plantings.