Long-headed poppy
Other names
Blaver, blind eyes, cock
Latin names
Papaver dubium L.
Weed Type
Annual Broad-leaved Weeds
Occurrence
Long-headed poppy is an annual or overwintering weed of arable land especially cornfields and of waste places and roadsides. It has a similar distribution to the common poppy but extends further north and is more frequent in Wales. The distribution on upland areas is limited by the lack of cultivated land but it has been recorded at 1,400 ft. It is found on light, dry, sandy and gravely soils but also flourishes on heavy land. The plant can withstand drought and occurs in quite arid areas. It was considered to be comparatively rare in the early 20th century but 50 years later it had become universally common.
Long-headed poppy is very variable and the size, growth habit, capsule number and flower shape of the plant are greatly modified by the environment. In open situations it forms a flat rosette of leaves. In poor or waterlogged soils plants may be small with few capsules. A white flowered form has been recorded.
Biology
The long-headed poppy flowers from May to July. It is self-fertile but the anthers are positioned below the stigmas to favour outbreeding. Poppies are normally insect pollinated, with honey and bumble bees the main pollinators. It takes 5-6 weeks from pollination to dehiscence of the seed capsule. Under very favourable conditions a plant may bear 100 to 200 capsules each containing 800 to 900 seeds. The average seed number per plant is given as 5,700 but output can vary from just 10 seeds up to 160,000.
The fresh seeds are inherently dormant and normally will not germinate at all for several months but then germination occurs sporadically over many years. Seeds may germinate if the seedcoat is damaged. Light does not appear to stimulate germination even after a period of stratification overwinter. Seed from green capsules that have been dried are viable and after over-wintering may germinate appreciably in February. The fully ripe seeds germinate in spring and autumn. The main period of emergence is in the autumn but the seedlings are susceptible to frost and winter losses can be high. Plants that survive the winter flower the following summer but earlier than seedlings that emerge in the spring.
Persistence and Spread
The seeds can remain viable in soil for a very long time. Seeds recovered from excavations and dated at 50 years old are reported to have germinated.
The wind shakes the seeds from pores in the seed capsule but does not disperse them further.
Seedlings have been raised from the droppings of various birds.
Management
Where seed shedding has occurred, keeping the seed at or near the soil surface will encourage spring germination. Shallow cultivations in spring will destroy the emerged seedlings. Deep cultivation should be avoided as it will bury the fresh seed and bring previously buried seeds to the surface.
Long headed poppy seed is susceptible to soil solarization.
The plant is attacked by a gall midge, Dasyneura papaveris, that causes the seed capsule to swell into a ball shape.