THE EVENING-PRIMROSES OF SASKATCHEWAN DIANA BIZECKI ROBSON, 811 Avenue E North, Saskatoon, SK S7L 1S7

Introduction total. The common name tends to cause some confusion. One would This article describes some of the think that the evening-primroses are general characteristics of the Evening- primroses which bloom in the eve¬ primroses (genus Oenothera) and ning.11 In fact, they are unrelated to presents a taxonomic treatment of the primroses (Primula species), and the genus consisting of a dichoto¬ while some species do bloom in the mous key, descriptions and habitat early evening, others bloom in the information. morning.11 Those species which flower in the evening are pollinated The common name evening- by nocturnal insects like moths.6 In primrose refers to both the family some species, the flowers will bloom Onagraceae and the genus Oeno¬ in one colour and then fade to a dif¬ thera. In this article it will refer to the ferent colour as the day wears on. latter. The evening-primroses are For example, Rock Rose (Oenothera closely related to the Willow-herbs caespitosa) (Figure 1) and White (Epilobium species), Butterfly-weeds Evening-primrose (O. nuttallii) (Fig¬ (Gaura species) and Enchanter’s ure 2) have white flowers that turn Nightshades (Circaea species). pink later in the day.7 Yellow Lau- Evening-primroses are widespread vauxia (O. flava) blooms yellow and throughout the world. In Saskatche¬ then turns pink.7 wan, there are seven species in Evening-primroses occur on dry, eroded areas and around slough margins. Yellow Evening-primrose (O. biennis) (Figure 3) and White Evening-primrose are the most com¬ mon species due to their “weedy” na¬ ture; they are found at the edges of fields and roads in sandy soil. Taraxia (O. breviflora) and Yellow Lavauxia occur on heavy clay soils near sloughs. Rock Rose prefers eroded, clay soils whereas Upland Evening-primrose (O. andina) prefers eroded, sandy soils.

Two of our native evening-prim- roses are considered to be rare in Canada: Upland Evening-primrose (Figure 4) and Taraxia (Figure 5).1 These two species are often placed in another genus: Camissonia. Two Figure 1. Rock Rose (Oenothera other species of evening-primrose, caespitosa). Rock Rose (Figure 6) and Yellow

55(3). September 1997 171 Figure 2. White Evening-primrose (Oenothera nuttallii).

Lavauxia (Figure 7), were consid¬ important uses. Evening-primrose oil ered rare in the past but are now is a source of gamma linolenic acid considered only uncommon.5 and is available at many health food stores.3 Research suggests that the The evening-primroses have several oil may be useful in treating eczema, asthma, migraines, inflammations, diabetes and arthritis.6 The oil may also act as an anti-clotting device.6 Native Americans made a tea from Yellow Evening-primrose roots to treat obesity and bowel pains.6 The young shoots of Yellow Evening- primrose can be put in salads and the roots can be boiled and con¬ sumed.6 Many members of this ge¬ nus are attractive from a horticultural perspective. Unfortunately, germina¬ tion studies have only been done for Yellow Evening-primrose and Rock Rose. Yellow Evening-primrose has been successfully cultivated as the seeds have a high germination rate when stratified.2 Rock Roses have beautiful flowers but the seed set Figure 3. Inflorescence, capsules and and germination are poor.2 Regard¬ rootstock of Yellow Evening-primrose ing tourism, the evening-primroses (Oenothera biennis). are attractive to nature lovers

172 Blue Jay 110* 102° • I I I I

Figure 4. Distribution of Upland Evening- Figure 5. Distribution of Taraxia (Oeno¬ primrose (Oenothera andina). thera breviflora). because of their large, beautiful, fra¬ while those with stems are consider¬ grant flowers. Ecologically, evening- ably taller (5 dm to 15 dm). The primroses provide nectar for many leaves are alternate on plants with species of insects and colonize stems and arise from the base of the eroded areas preventing soil erosion. plant in stemless species.

The evening-primroses are easy The flowers are yellow, white or to identify with their four distinctive, pink and often change colour with heart-shaped petals, four-lobed stig¬ age. They are usually large and con¬ mas and eight stamens with the an¬ spicuous but wither soon after flow¬ thers attached to the filaments near ering. There are four sepals and four the middle (Figure 8). The leaves petals. These floral parts are partly and either the flowers or fruits are suf¬ fused at the base to form a cup-like ficient for identification of the species. structure called a hypanthium (Fig¬ ure 8). The hypanthium is fused to Description of Oenothera4,7,8,10 the ovary of the plant.

This genus contains annual, bien¬ One of the most distinctive fea¬ nial and perennial species. Some tures is the four-lobed stigma espe¬ species lack stems; their leaves and cially noticeable when deeply lobed, flowers arise directly from the forming a cross. The ovary occurs ground. Rarely, the plants are woody below the point of attachment of the at the base. Oenothera species vary sepals, petals and stamens, a posi¬ in height. The stemless plants are tion that is referred to as “inferior.” quite short, from 3 cm to 10 cm, The ovary has four chambers that

55(3). September 1997 173 no* 102® • i i i i no® ,02® I I I I

Figure 6. Distribution of Rock Rose Figure 7. Distribution of Yellow Lavauxia (Oenothera caespitosa). (Oenothera Flava). can be seen by cutting the ovary are equal in length while in others crosswise. The ovaries mature into the stamens opposite the petals four-chambered capsules that con¬ (rather than between the petals) are tain numerous smooth seeds. shorter. The anthers of the stamens are attached to the filament at their There are eight stamens in each midpoint, making them rock back flower. In some species the stamens and forth like a teeter-totter.

9 Figure 8. Floral diagrams of Oenothera.

174 Blue Jay Identification Key to the low aging to pink; capsule with wings Native Evening-primroses of at the margin, to 2 cm long; leaves to Saskatchewan4*810 1.5 cm broad, deeply divided on the la. Plants with leafy stems; flowers lower third, the terminal portion entire usually several in leafy spikes (flow¬ or with wavy lobes - O. flava ers attached directly to the main Descriptions of Native stem) or racemes (flowers attached Evening-primroses4,7,8,10 to the main stem by short stalks) - 2 The plants are arranged alpha¬ lb. Plants without leafy stems; flow¬ betically according to the scientific ers single on stalks arising from the name as many of the plants have base of the plant; leaves arising from more than one common name. After the base of the plant - 5 each scientific name there is a list of 2a. Plants shrubby, usually with sev¬ the synonyms for that species. A eral slender brown, woody stems; synonym is another scientific name stigma not deeply divided into four that is used. lobes; flowers yellow with a trumpet¬ shaped base - O. serrulata 1. Upland Evening-primrose or An¬ dean Sundrops/Oenothera andina 2b. Plants not shrubby; stems not Nutt. [Camissonia andina (Nutt.) brown and woody; stigma deeply di¬ Raven; Sphaerostigma andinum vided into four lobes - 3 (Nutt.) Walp.] 3a. Annual; stems 3-10 cm tall, slen¬ This species is an annual plant der, branched; flowers small, 1-3 mm with slender stems that branch from long - O. andina the base. The stems are covered 3b. Biennial or perennial; stems with fine hairs. The plant ranges from taller, stout; flowers larger, more than 3 to 10 cm in height. The leaves are 5 mm long - 4 alternate, smooth margined and lin¬ 4a. Biennial; flowers yellow, buds ear or narrowly oblanceolate (lance¬ erect; stem green or reddish, not shaped with the broadest part at the much branched; seeds in two rows; tip of the leaf). The leaves are 1 to 3 leaves oblong to lance-shaped - O. cm long. The flowers are yellow and biennis clustered in the axils of the leaves. The petals are 1 to 1.5 mm long. The 4b. Perennial; flowers white or pink¬ stigma is rounded. Capsules are 5 to ish, buds nodding; stems white with 6 mm long, spindle-shaped, greyish shreddy bark, usually much and with four angles. This plant is branched; seeds in one row; leaves rare and occurs on dry sandy slopes linear to lance-shaped - O. nuttallii in the western Prairies. 5a. Stigma with four linear lobes; pet¬ als greater than 1 cm - 6 2. Yellow or Common Evening- primrose/Oenothera biennis L. 5b. Stigma rounded, very slightly lobed; petals less than 1 cm, yellow; This species is a biennial plant leaves divided into wavy lobes - O. with a stout taproot. It forms a leafy breviflora rosette in the first year and an erect, stiff stem in the second year when it 6a. Petals greater than 25 mm long, grows to 5-15 dm tall and usually white aging to pink; capsule not has branches. The stems are greyish winged, to 4 cm long; leaves to 2.5 or reddish in colour and are covered cm broad, leaf margins are straight with small hairs. The leaves are or with teeth - O. caespitosa ascending or spreading and are 6b. Petals less than 25 mm long, yel¬ attached directly to the stem. Leaves

55(3). September 1997 175 are lance-shaped or somewhat oval, wavy on the margins. The leaf stalks densely or sparsely hairy and some¬ are winged. The flowers are sessile times with small teeth on the edges. in the crown of the plant and have a The leaves vary in length from 2 to sweet scent. The hypanthium tube is 14 cm. The flowers are in leafy, ter¬ 3 to 10 cm long. The petals are 2 to minal spikes. The large, yellow flow¬ 4 cm long. When the petals open in ers are erect and open in the the morning they are white, but they evening. The hypanthium tube is fade to pink later in the day. The about 3 cm long. The sepals are stigma is deeply divided into four lin¬ united at first except for very short ear lobes. The capsules are about free tips and later separate and bend 2.5 cm long, woody and four-angled; back. The petals are 12 to 25 mm the angles having wavy crests on long. The stigma is deeply divided them. Sometimes the capsules have into four lobes. Capsules are 2 to 3 small bumps on them called tuber¬ cm long, erect and with small hairs. cles. Rock Rose blooms from May to The plants are in bloom from July to August. It is not common and is October. This species is very com¬ found on dry hillsides of gumbo or mon on lighter soils throughout the clay soil and sometimes on gumbo southwestern portion of the Prairies flats throughout the Prairies. and occasionally in the boreal forest. 5. Yellow Lavauxia/Oenothera flava 3. Taraxia/Oenothera breviflora T. & (A. Nels.) Garrett [Lavauxia flava A. G. [Camissonia breviflora (T. & G.) Nels.] Raven; Taraxia breviflora (T. & G.) Yellow Lavauxia is a stemless per¬ Nutt.] ennial with a fleshy taproot and ro¬ Taraxia is a stemless, perennial sette of leaves near the ground. The species with a rosette of leaves leaves are 1 to 2 dm long, oblanceo¬ close to the ground. The leaves are late in shape, deeply divided and 5 to 12 cm long, deeply divided and coarsely toothed. The midrib of the covered with fine hairs. The petals leaves on the underside is very are 5 to 8 mm long. When the petals prominent. The leaves are some¬ first open they are yellow; as they times hairy on the margin. The hy¬ dry out they turn red. The stigma is panthium tube is 4 to 7 cm long. The knobbed. The capsules are about petals are 12 to 18 mm long. When 1.5 cm long, narrowly oval and cov¬ they first bloom they are yellow; later ered with hairs. This species is very in the day they turn pink. The stigma rare and is found on heavy clay soils has four linear lobes. The capsules of slough margins in the western are 2 to 3 cm long, four-angled, with Prairies. winged edges. The plants are in bloom from May to August. This spe¬ 4. Rock Rose, Butte Primrose, cies is not very common and can be Gumbo or Tufted Evening-primrose/ found in valleys, slough margins, Oenothera caespitosa Nutt. [Pachy- clay flats and drainage channels in lophus caespitosus (Nutt.) Raim.] the western Prairies. This species is a perennial with a thick, woody root. The plants are 6. White Evening-primrose/Oeno- stemless or nearly so. The leaves thera nuttallii Sweet [Anogra nuttallii are lance-shaped to oblanceolate, (Sweet) A. Nels.] sometimes with small hairs on the This species is a perennial with a margins. The leaves are 1-2 dm in white fleshy rootstock. The erect length and are sometimes toothed or stems are white, somewhat shiny

176 Blue Jay and have shreddy bark. The stems cies is not common and can be are often branched. The plant ranges found on dry, sandy prairie and hill¬ in height from 4 to 10 dm. The leaves sides in the Prairies and parkland. are 5 to 10 cm long. The leaves are linear to linear-oblong and taper at Literature Cited the base. The upper leaf surface has no hairs but there are hairs beneath 1. ARGUS, G.W. and K.M. PRYER. the leaves. The flowers have an un¬ 1990. Rare vascular plants in Can¬ ada. Canadian Museum of Nature, pleasant scent. The drooping flowers Ottawa. grow out of the leaf axils. The hypan- thium tube is 2 to 2.5 cm long. The 2. CURRAH, R., A. SMRECIU and M. petals are about 2 cm long. Like the VAN DYK. 1983. Prairie wildflowers. Friends of the Devonian Botanic Gar¬ Rock Rose, the petals of this species den, University of Alberta, Edmonton. are white when they open and pink at the end of the day. The stigma is 3. FOSTER, S. and J.A. DUKE. 1990. Eastern/Central medicinal plants. deeply divided into four lobes. The Houghton Miffin Co., Boston. capsules are 2 to 3 cm long, slender, somewhat curved and four-angled. 4. GREAT PLAINS FLORA ASSOCIA¬ TION. 1986. Flora of the Great Plains. They are in flower from June to Sep¬ University Press of Kansas, tember. This species is very com¬ Lawrence, Kansas. mon and is found on roadsides in light or sandy soils in the Prairies 5. HARMS, V.L., P.A. RYAN and J.A. HARALDSON. 1992. The rare and and parkland. It is persistent on culti¬ endangered vascular plants of Sas¬ vated fields. katchewan. The W.P. Fraser Herbar¬ ium, University of Saskatchewan, 7. Shrubby Evening-primrose / Oe¬ Saskatoon. nothera serrulata Nutt. [Calylophus 6. JOHNSON, D., L. KERSHAW, A. serrulatus (Nutt.) Raven; Meriolix MACKINNON and J. POJAR. 1995. serrulata (Nutt.) Walp.] Plants of the western boreal forest and aspen parkland. Lone Pine Pub¬ This perennial species has a lishing, Edmonton, Alberta. woody base. The plants range in 7. LOOMAN, J. and K.F. BEST. 1979. height from 1 to 5 dm. The stems are Budd’s flora of the Canadian prairie slender, brown and erect or decum¬ provinces. Canadian Government bent. The leafy branches are more or Publishing Center, Supply and Serv¬ less hairy. The leaves are 2-5 cm ices Canada, Hull, Quebec. long, alternate, spatula shaped, lin¬ 8. MOSS, E.H. 1983. Flora of Alberta. ear or linear oblong. The leaf mar¬ University of Toronto Press, Toronto. gins are finely toothed or toothless, 9. PORTER, C.L. 1959. Taxonomy of and often with short, stiff hairs. The flowering plants. W.H. Freeman and flowers grow out of the axils of the Company, San Francisco. upper leaves. The hypanthium is 10. SCOGGAN, H.J. 1979. The flora of trumpet-shaped and four-angled. Canada. National Museum of Natural The sepals have a ridge down the Sciences, National Museums of Can¬ back. The petals are yellow and ada, Ottawa. wavy on the margins. The stigma is 11. WERNERT, S.J. 1982. North Ameri¬ disc-shaped and shallowly four- can wildlife. Reader’s Digest Associa¬ lobed. The capsule is slender, grey¬ tion, Inc., Pleasantville, NY. ish and 15 to 25 mm long. This spe¬

55(3). September 1997 177