Family: Onagraceae
Genus: Oenothera
Species: biennis
(i) General background on the plant
Evening primrose is a native of North America and was introduced into European botanical gardens in 1614 from Virginia, USA. It has since become a wild plant and is a familiar sight on roadsides, dunes, railway banks and waste places. It grows as far north as 65° N in Finland.
It is a biennial plant. In the wild seed germinates in the spring and in the first year the plant forms a rosette of leaves which is flat to the ground and which may grow up to 30 cm across by the autumn. This maximises overwintering survival chances. In the spring of the second (reproductive) year the plant produces a central stem with a variable number of branches; it grows to a height of 20-200 cm. Each stem bears numerous yellow blooms which open in the evening. Flowering normally starts in July and fresh flowers are produced each day for several months. They are self-pollinated but some are cross-pollinated and they can be pollinated by moths.
The sepals are green, and the yellow petals are broader than they are long (15-30 mm). After pollination, a long seed pod is formed which is divided longitudinally into 4 compartments, each containing many tiny seeds (diameter 1mm). The seeds mature from September to October and have a minimum 1000 grain weight of 500 mg.
(ii) Details of quality characters
Evening Primrose oil composition [3]:
>70% linoleic acid (C18:2)
9 - 10% g (gamma) linolenic acid.
Seed constituents by weight [3]:
| Protein | 15% |
| Cellulose + Lignin | 43% |
| Oil | 24% |
(iii) Current production and yields
Theoretically the crop has a potential yield of 2.5 t/ha, actual yields are between 0.49 and 1.2 t/ha for a biennial crop and 0.57 and 0.74 t/ha for an annual crop. 500 ha grown in 1990. (4)
(iv) Constraints on production
- Cabbage stem flea beetle (Psylloides chrysocephala) may be a problem. Altica spp. have defoliated evening primrose.
- Desiccation is necessary because pod ripening occurs successively up the stem over a wide span of time, often splitting when ripe allowing seed to shed.
- Pod sealants are being investigated to reduce pod shatter. (5)
(v) Markets and market potential
Uses:
Although the roots and various parts of the plant can be eaten, the main interest in producing the plant is that the seeds are a good source of g -linolenic acid. It also contains tocopherol, tryptophan, sitosterol and vitamin B. g - linolenic acid is an essential fatty acid in human metabolism i.e. it cannot be synthesised in the body and is required by the body for various functions e.g. neurotransmitter synthesis, healthy skin [3].
Evening primrose oil is also sold as a dietary supplement in health food shops.
The seed is also a good source of tryptophan for which there are numerous medical applications
(vi) Other information
In cultivation the seed of biennial types is sown late July, early August, so the plant becomes large enough to overwinter and then set seed for the following September / October. Annual types are drilled in spring. Soil should be worked to a fine tilth and seeds are shallowly drilled. Irrigation may be necessary to encourage germination at the correct time. A crop density of 30 plants per m2 is optimum to encourage even maturity. Weed control may be necessary during the rosette stage and chemicals are available. Nitrogen is applied in late spring (50kg/ha). Harvesting is usually late September or early October.
See the following pages in the NF-2000 Database
Evening primrose (Oenothera spp.)
Crops for Pharmaceuticals/Cosmetics
(vii) Contacts
Peter Lapinskas, 26 Deepdene Wood, Dorking, Surrey RH5 4BQ, United Kingdom
Tel: +44 (0) 1306 88 25 28
Fax: +44 (0) 1306 88 25 28
E-mail: Peter@Lapinskas.com
Website: www.Lapinskas.com
(viii) References
1. Flora of the British Isles; Clapham, A. R.; Tutin, T. G. & Moore, D. M.; (1987) 3rd Edition. Published Cambridge University Press
2. New Crops For Temperate Regions. Edited by Anthony, K. R. M.; Meadley, J. & Röbbelen, G.; Published 1993 by Chapman and Hall
3. CRC Handbook of Alternative Cash Crops; Duke, J. A., duCellier, J. L. Published 1993 by CRC Press, Inc. USA.
4. Anon Demonstration plots, UK 1990.
5. BASF Alternative crop production