bearbine, bethbine, cornbine, field convolvulus, wild convolvulus
Convolvulus arvensis L.
A pernicious perennial weed, native in cultivated land, roadsides, railways, grass banks and in short turf. Field bindweed is found throughout England, Wales and Ireland but is rare in Scotland. It is not recorded above 1,000 ft in the UK. It occurs on almost all soils on both heavy and light land. Field bindweed can survive long periods of drought due to its extensive root system.
Field bindweed is found in many different crops but is a particular problem in cereals and in perennial crops. It trails over the ground and climbs among the crops pulling them down and hindering harvesting. In a survey of cereal field margins, field bindweed was one of the most frequent species recorded.
Plants from different populations may differ in leaf shape and flowering habit. Some of this is due to habitat but distinct clones have developed that are self-incompatible and only set seed when cross-pollinated by another clone.
Field bindweed has medicinal uses as a mild laxative and as a diuretic. It is an alternate host of the potato X virus.
Field bindweed flowers from June to September. The flowers are insect pollinated and most pollen is deposited up to 4 m from source. Clones are self-incompatible and differ in the timing and capacity for flowering. Seed is set from August to October. There are 1-4 seeds per capsule. The average seed number per plant is 600 but fewer seeds are produced when plants are growing in a competitive crop. Seed production is greater in hot dry summers. Seeds can become viable 10-15 days after flower pollination. The seed coat hardens and becomes impermeable as the seeds ripen. The hard seed coat is responsible for dormancy. Seeds on plants cut down after flowering have thinner seed coats, at least initially, and may germinate at once. Damage to the seed coat results in faster germination.
Some seeds germinate in autumn and others at intervals through the year but most seedlings emerge in late spring. A seedling may flower and fruit in its first year if conditions are favourable. Seedlings rapidly develop a vertical taproot from which lateral roots are produced mainly in the upper 30 cm of soil. These grow out horizontally for 45 to 75 cm before turning down to form secondary vertical roots. These give rise to more laterals that again turn down to form verticals and so on. Roots may reach 1.2 m deep after 1 year and 4 m after 2.5 years. New shoots form mainly at the point where laterals turn down vertically. Less commonly, shoots form along the horizontal portion of the lateral roots. Apart from the initial aerial shoot, all other shoots originate from root borne stem buds that give rise to vertical underground stems or rhizomes. At nodes along the rhizomes are buds that can develop into branch rhizomes. The rhizomes are stout but brittle and often spirally twisted. The majority of the roots and rhizomes are in the upper 60 cm of soil.
The shoots appear above ground in May and persist until the hard frosts. Field bindweed overwinters by means of roots and rhizomes. Roots in the upper layers may be killed by a penetrating frost and most lateral roots die back each year but some persist and spread horizontally. New growths arise in spring from buds formed in the autumn on lateral roots that survive the winter.
Over 95% of seeds are hard-coated and can lie dormant in soil for more than 28 years. Seedlings continued to emerge for over 20 years after all the adult plants were removed from an area. It has been suggested that seeds can remain viable for up to 3 months in dung and compost. The seeds can also survive in silage.
Seeds can remain viable in the stomachs of migrating birds. Field bindweed seed is not a common contaminant of crop seeds other than cereals. Seed and rhizome fragments may be spread in soil. Initial spread may be by seed but once established, vegetative spread is more important. Field bindweed spreads mainly as fragments of rootstock that are able to produce new plants. A 5 cm length of vertical root can regenerate and produce a new plant. Once established, a plant can spread radially up to 3 m per year. Field bindweed plants are often associated with the edges of arable fields but even when it is common in the hedge bottom it rarely spreads far into the field.
Avoid introducing seeds and rhizome fragments from contaminated areas into fields that are free of the weed.
The depth of the root system makes it impossible to remove by cultivation alone. Only by exhaustion and removal of the rootstock can field bindweed be eradicated. In field crops this entails short rotations with extra root crops and persistent hoeing. During tillage operations the rootstocks can be collected by harrows or by hand and these should be burnt. Turning up the rootstocks to dry in the sun during summer fallowing will reduce the weed. Sometimes only the more drastic bare fallowing with regular cultivations will reduce it appreciably. New shoots arise within 7-14 days of shoots being hoed off. Field bindweed often responds to injury by producing more shoots than were originally cut back. Repeated cultivations, up to 25 over a period of 2-3 years, may eradicate the weed. The optimum interval between cultivations is considered to be 12 days after regenerating shoots emerge, the longer the interval the more prolonged the period before control is achieved. However cultivating every 2 weeks initially and every 3 weeks later in the year is more practical. The only benefit of deeper cultivations is that shallow ones require a shorter the interval between operations.
It is important to hoe off seedlings soon after they emerge. Most 20-day old seedlings (4-leaf stage) cut off just below the soil surface are able to regenerate after decapitation but younger seedlings are less likely to regrow. Seedlings over 6 weeks old are unlikely to be killed by shallow cultivation. In arable situations a dense crop stand may out-compete bindweed seedlings. In perennial crops, the period before planting is the main opportunity to deal with the weed.
In roadside verges, cutting frequency had no effect on the occurrence of field bindweed. Field bindweed is not common in grassland and is unlikely to appear in closely grazed pasture. When it does occur, harrowing in spring may help to keep it down. Sheep and cattle eat the foliage and pigs and chickens may unearth and consume the underground stems and fleshy roots.
Field bindweed seed is moderately susceptible to soil solarization. Entire or woven black plastic or other fabric sheeting will suppress field bindweed emergence but the cost can only be justified in long-term or high value crops. The weed can survive under black plastic sheeting for at least 6 months.
Biological control with fungal pathogens of the genus Septoria and of the genus Phoma has been investigated. The species demonstrate sufficient pathogenicity and host specificity to be regarded as promising biocontrol agents. The host-specific fungus, Erysiphe convolvuli, has also been evaluated as a potential biocontrol agent of field bindweed. An inoculum of the fungus Phomopsis convolvulus has caused severe damage to field bindweed plants at all growth stages. The extent of the damage varied with plant age. Seedlings at early leaf stages were more sensitive than established plants. Timing and weather conditions are critical if biological control is to be effective.
Updated October 2007.