Wild garlic and crow garlic

Wild garlic or ramsoms are a pleasing sight in British woodlands, producing a haze of white flowers from April to June. The leaves are edible and add a garlic flavour to salads. However, their persistent bulbs and spreading habit make them a problem in most gardens. The less common but equally persistent crow garlic can also be a nuisance.

Wild garlic. Image: Mike Grant/RHS

Quick facts

Common name Wild garlic, ramsons; crow garlic 
Botanical name Allium ursinum (wild garlic); A. vineale (crow garlic)
Areas affected Beds, borders and uncultivated areas
Main causes Bulbous plants that spread by bulbs or bulbils
Timing Seen late autumn to mid-summer; treat late autumn to mid-winter

What are they?

Wild garlic or ramsons (Allium ursinum) and crow garlic (A. vineale) are bulbous plants native to Britain that can be problematic in gardens.

Appearance

Wild garlic (Allium ursinum) often grows in large, dense colonies. The long, elliptic leaves are accompanied by angular (triquetrous or three-sided) flowering stems from April to June with umbels of white flowers at the top. Plants may reach 50cm (20in) in height.

Crow garlic (Allium vineale) has more slender, rounded flowering stems and tubular leaves. It can reach up to 1.2m (4ft) in height. The actual flowers are very small but there are usually few of these in the flowering head which instead is made up of small, purplish bulbils. Flowering time is June to August.

The problem

Wild garlic spreads by the production of underground bulbs, whereas crow garlic spreads easily by bulbils which form in the flowers. These bulbils may remain dormant in the soil for up to six years.

The bulbs and bulbils can also persist in garden compost heaps.

Control

Non-chemical control

Consider non-chemical options first;

On loose or light soils, remove all bulbs with a hand fork or trowel. This is a laborious task and will only be effective if done thoroughly, perhaps even resorting to sieving the soil to ensure all small bulbs and bulbils are removed.

Putting infested beds down to grass does not prevent the growth of the bulbs, but small infestations may be almost eliminated by replacing the topsoil to at least a spade's depth.

An alternative method is to cultivate the soil during dry conditions in November or late January, when the bulbs are in growth and most susceptible to disturbance. This will weaken them and may prevent flowering and the production of bulbils, but do not dig from August to early October, when the bulbs are dormant, as this will simply spread the bulbils around.

Caution: do not dispose of bulbs or bulbils by adding them to the garden compost heap.

Chemical control

Among other bulbs

Unfortunately, when the wild garlic or crow garlic are found growing amongst other bulbous plants no weedkiller will kill them without also harming or destroying the cultivated plants by absorption through their leaves and roots.

Glyphosate

  • Use glyphosate-based weedkillers (e.g. Scotts Roundup, Bayer Garden Rootkill Weedkiller or Doff Glyphosate Weedkiller) around the woody bases of well-established trees and shrubs, as it is not readily absorbed by woody tissue
  • Around low-growing shrubs and perennials shield the cultivated plants from the spray until it has dried on the weed
  • Glyphosate can also be used on paths and drives (e.g. Westland Resolva Path & Patio range (also contains diquat), Doff Path & Patio Weedkiller or Westland Deep Root Ultra Tree Stump Weedkiller)
  • The most effective period for spraying is probably just before flowering
  • Try lightly bruising, by trampling or beating with a spade, of the stems and leaves of the allium before spraying to help absorption of the weedkiller

Control may not necessarily be achieved in a single season.

Residual control

Bayer Garden Path & Drive Weedkiller and Scotts Weedol Pathclear products containing glyphosate/diflufenican and can be applied once a season to natural surfaces where no plants are to be grown, and can also be applied under and around established woody trees and shrubs. This product kills off existing small green growth and prevents or checks developing growth. It could also help to check early growth, particularly of small bulbs and bulbils. Check manufacturer’s recommendations before use to avoid damaging sensitive plants.

Inclusion of a weedkiller product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener.

Downloads

Weedkillers for gardeners (Adobe Acrobat pdf document outlining different weedkillers available for gardeners; see sections 4 and 5)

Links

Chemicals: applying with a sprayer
Chemicals: using safely and effectively
Chemicals: using spot and broad-scale weedkillers
Weeds: non-chemical control

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