Plants of the Eloise Butler Wildflower Garden

The Evening Primrose's are generally known for flowers that close during daylight hours, although the flowers are usually partially open until noon, especially on cloudy days. Common Evening Primrose is an erect native biennial (or occasionally perennial) rising up to 6 feet in height on a usually unbranched stem. The stem is green with some reddish tones, ridged and usually has fine white hair.

The leaves are both basal and stem. Basal leaves taper to short stalks and form a rosette in the first year of growth. The stem leaves develop the second year when the flowering stem rises; they are alternate, lance-like, wavy edged, slightly toothed, slightly hairy on both surfaces, with one main central vein and fine laterals. They can be up to 8 inches long near the base and 1/4 as wide, but become considerable shorter near the top of the stem. Some leaves tend to have a twist at the tip. The upper leaves are sessile. There are usually much smaller secondary leaves showing in the leaf axils.

The inflorescence is a stiff, terminal flower spike of many flowers which open from the base of the spike and progress upward as the spike elongates. Short side branches in the inflorescence are not uncommon.

The flowers are 4-part, fragrant, from 3/4 to 2 inches wide with yellow corollas. They appear to have stalks but are really sessile - the calyx tube is quite long, slightly hairy, greenish with the ovary at the base right next to the stem of the inflorescence. There is a small linear floral bract at the base of the tube. The petals are widest at the broad rounded tip, which has a slight notch. The bases are very narrow. There are four greenish-yellow sepals which are longer than the petals, very linear and reflexed back to the corolla tube when the flower opens. There are 8 stamens with yellow filaments and anthers, the anthers linear and quite long. The single style has a greenish 4-cleft stigma.

Seed: As the blooming flowers move upward, seed capsules, or pods, which are thicker at their base and about 1-1/4 inch long, form under them in a spiral pattern around the spike. These are stiff and hard, composed of 4 chambers (valves) and contain 300 to 400 very small reddish brown seeds per capsule (apprx. 90,000 to the ounce). The capsule opens at the top, seeds are dispersed by wind shaking the stem. Seeds can germinate in four weeks and will form a rosette, then the plant over-winters and flowers the following year. Seeds germinate best in cool soil and need light to germinate, hence they should be surface sown. If seeds are stored it should be in cold but dry storage. Cold moist stratification is not needed.

Habitat: Common Evening Primrose grows from a branching taproot and spreads via re-seeding. It prefers full sun, average moisture to dry (wet-mesic to dry) and well drained soil. It is adaptable to a number of sunny locations and will be found in fields, roadsides, abandoned areas, thickets and drier banks, etc.

Names: There are a number of similar species confusingly using the common name although those other species have available more appropriate names. The genus name Oenothera, comes from two Greek words, oinos for "wine" and thera for "to imbibe". This is an old name give by Theophrastus (371-286 BC), a pupil of ARISTOTLE and the first important botanist of antiquity, to an unidentified plant, whose roots when eaten and were said to establish a desire for wine - others say it would do away with the effects of wine. Still others think it is a coruption of the Greek onotheras which refers to a chase or a hunt or a pursuit. All meaningless today. The species name, biennis, refers to the biennial character of the 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. An older scientific name, still in use in Martha Crone's time is Oenothera muricata.

Comparisons: A much shorter Oenothera in the Garden is Prairie Sundrops, O. pilosella, which is not native to the state.