corn speedwell, ivy chickweed, winter-weed
Veronica hederifolia L. (V. hederaefolia)
A native annual, common in cultivated ground throughout the UK. It is not recorded above 1,250 ft. Ivy-leaved speedwell is said to be an indicator of nutrient-rich loams but is also common on clay soils.
It is frequently seen in winter cereals especially on heavy land.
Two sub-species occur, ssp. lucorum with smaller lilac flowers and ssp. hederifolia with larger blue flowers. The former occurs mainly in gardens and shady places, the latter in cultivated fields and by roadsides. Around 1 in 1,000 seedlings have 3 cotyledons.
Ivy-leaved speedwell flowers from March to June or possibly even into August. There are 2 seeds per seed capsule. The average seed number per plant ranges from 40 to 400 but there can 1,200 in plants on open sites. Seed number is closely correlated with plant weight. Ivy-leaved speedwell can be found in fruit for 5 months of the year.
Ripe seed is dormant but after 1-2 months burial in soil it will germinate at low temperatures. Dormancy is overcome by warm summer temperatures and gradually re-imposed by low winter temperatures. The main period of seedling emergence begins in October and continues until May.
In a sandy loam soil, seedlings emerge from the top 110 mm of soil with most emerging from between 5 and 60 mm deep. Few seedlings emerge from the surface 0-5 mm.
Seed longevity in soil is at least 3-4 years. Seed mixed with soil and left undisturbed had declined by 65% after 6 years but in cultivated soil the decline was 99%. Seed sown in a succession of autumn-sown crops in soil ploughed annually had an annual decline of 57%. The estimated time to 99% decline was 5.4 years. Emerged seedlings represented 2% of the seedbank. In grassland soil, ivy-leaved speedwell seed had a mean annual decline of 19% and a half-life of 3.5 years.
Apparently-viable seed has been found in cattle droppings.
Only clean crop seed should be sown. Control is by surface cultivations in spring. Cereals should be harrowed well early in the season. In winter wheat, ivy-leaved speedwell is favoured by poor crop establishment and by early applications of nitrogen fertilizer. Ivy-leaved speedwell germinates primarily in autumn-winter and has been found to gradually disappear following a series of spring cereals.
Fallowing for a year generally reduces weed seed numbers in soil but prevailing weather conditions can influence this. There is a similar reduction in seed numbers following a well-managed winter wheat crop.
Updated October 2007.