bledewort, corn poppy, corn rose, field poppy, redweed, thunder flower
Papaver rhoeas L.
Common poppy is an annual or overwintering weed native in arable land, roadsides, waste places and other disturbed habitats. It occurs mainly in England and SE Scotland but is rarer in Wales and much of Scotland. It is not recorded above 1,000 ft in Britain. Common poppy is a frequent weed of cornfields on light, dry, sandy and gravely soils, and to a lesser extent on heavy land. It is often associated with soil of pH 6.0 to 8.0. Soil seedbank numbers of between 2.5 and 20 million seeds per ha have been recorded for common poppy in vegetable fields in the UK.
Numerous forms and varieties have been recognised. Leaf shape and hairiness are very variable characters. Albino and tricotyledonous seedlings appear occasionally. Common poppy populations that have developed resistance to certain herbicides have been recorded. The different poppy species often occur together but few natural hybrids have been found.
If eaten in large quantities common poppy is poisonous to livestock, the active principle is rhoeadene. The seeds produce a fine oil and are sometimes added to bread and cakes. Common poppy has medicinal uses including as a mild sedative. An infusion of petals applied to the skin is said to reduce wrinkles.
Flowering begins in mid-June with flushes in late-June and early-July and intermittent flowering then continues to October. A second flush of flowers may appear in the stubble after cereal harvest. Common poppy is normally the last of the poppies to start into flower and to finish but the seed capsules ripen the fastest. A plant may produce 1 to 400 flowers depending on soil fertility and the vegetation density. Poppies are usually insect-pollinated, however, the species is more or less self-fertile and, as the anthers dehisce before the flowers open, self-pollination can occur ahead of cross-pollination. Seed ripens and is shed 3-4 weeks after flowering. The mean number of seeds per capsule is 1,360. The average seed number per plant ranges from 10,000 to 60,000. An isolated plant may have more than 500,000 seeds. Seed numbers correlate well with plant dry weight.
In freshly shed seeds the embryos are underdeveloped and physiologically dormant. They require a period of burial in soil for several months to lose dormancy. Seed scarification does not improve germination but light promotes it.
Most seedlings emerge from February to April with a second smaller flush in August-October. Common poppy is therefore a weed in both spring and autumn cereals, although frost may kill the newly germinated seedlings. Seedlings in closed communities such as woodland or grassland rarely establish successfully.
In a sandy loam soil, field seedlings emerged from the top 30 mm soil with most emerging from the upper 15 mm. Emerged seedlings represent 1 to 8% of the viable common poppy seeds present in the soil.
Seed longevity in soil is more than 8 years. Common poppy seeds broadcast onto the soil surface, ploughed to 20 cm and followed over a 6-year period of cropping with winter or spring wheat had a mean annual decline rate of 9%. The estimated time to 95% decline ranged from 17 to over 50 years. In a separate trial the estimated time to 99% decline was 8.7 years and in a further study the annual decline rate was 40%. In undisturbed grassland common poppy seeds had a half-life of 11 years. Dry-stored seed gave 80% germination after 5 years.
Common poppy seeds are shaken from ripe capsules by the wind. The seeds travel up to 3 m initially but are small enough to be further wind dispersed. Birds eat the seeds and seedlings have been raised from their droppings. The seeds have been found as a contaminant in cereal and other crop seed.
Control is helped by ensuring that only clean crop seed is sown. Where seeding has occurred, keeping seed at or near the soil surface will encourage spring germination. Deep cultivation should be avoided. Harrowing in dry weather will destroy emerged seedlings. The inclusion of root crops in the rotation will help to reduce an overwhelming population.
In cereals, crop density is an important factor in reducing plant growth and hence seed numbers in common poppy. Annual post-emergence harrowing with occasional ploughing has given good results. Cutting seedlings, at or below the soil surface, or complete burial gives the best control. Partially buried seedlings with the roots still attached can recover. Fewer seedlings emerge from a coarse cloddy soil than a fine seedbed.
Fallowing has given a gradual reduction in seedbank numbers, but prolonged seed dormancy prevents a rapid decline. Fallowing every 5th year over a 15-year period reduced seed numbers progressively if good weed control was maintained in the intervening cropped years.
Updated November 2007.