KNOWING THE ENEMY

Denham Allotments least wanted!


Perennial weeds
Perennial weeds are more of a problem because they can live for several years. They survive the winter by storing food in their roots. These roots make them harder to get rid of than annual weeds. Some are difficult to dig out and others spread underground. If you leave even the tiniest piece of root in the soil when you dig them out, you'll get a whole new plant.
To control:
  • Dig out perennial weeds as soon as you see them. So long as you don't let them produce leaves, the roots will use up their energy stores and eventually die. Never rotavate soils with perennial weed infestations as it is a brilliant way of propagating them! Always dig out every little bit as they will regrow and often with twice the vigour.
  • If you don't mind using chemicals, treat them with a weedkiller containing glyphosate.
  • Never put perennial weed roots or seed-heads on to the compost heap, if allowed burn.

Bindweed

Calystegia sepium  

If the area that is infested is open ground, eg an unplanted allotment, apply sheet mulch (cardboard and wood chips) and give it a few months for the underground stems to come up to the surface. Then using a fork loosen the soil and pull all the visible stems and roots out, starting at one end and working your way across systematically to be as thorough as possible. Once you've removed as much as possible then mulch thickly again. This process might have to be repeated again next growing season. If the bindweed is present in garden beds and is entwined with other plants you first need to unwind it, but be careful as pulling and tugging can damage your good plants that you are trying to save. Unwind it as far to the base as you can and then loosen the soil around where you find the roots and remove as much as you can with a fork. Then BE PERSISTENT, keep pulling it out when you see it. DO NOT let it flower. Seeds can remain dormant in the soil for up to 20 years, but you can keep it under control if you keep removing it as you find it. If you can keep removing the foliage above ground, you'll force the plant to use up its energy reservoirs in its roots. The roots will begin to starve which will eventually kill it. After 2-3 years of ruthless weeding you should be able to almost eradicate this plant, Continue to remove even the smallest of bindweeds before the roots have developed and do not put removed weeds in a compost heap, as they will regrow from even the smallest section of root.

Broad Leaved Dock

Rumex obtusifolius 

Broad-leaved dock is a perennial weed most commonly found in neglected lawns and rough grassland. The plants have very deep tap roots enabling them to survive drought and poor nutrition soil types. Permanent control is not complicated provided that the timing of herbicide application is correct.

Dandelion

Taraxacum Spp 

Their large yellow flowers and furry seed heads make them easily recognisable. They often invade lawns and can be difficult to get rid of in the border and in cracks in paving. Best to stop them taking root by providing specimen plants with a surrounding weed-suppressing mulch. Established weeds can be dug out by hand, ensure you get all of the long tap root, or you can spot treat with a glyphosate stick - you may need to do this more than once.

Marestail / Horsetail

Equisetum arvense

 The creeping rhizomes of this pernicious plant may go down as deep as 2m (7ft) below the surface, making them hard to remove by digging out, especially if they invade a border. They often enter gardens by spreading underground from neighbouring properties or land.  Removing horsetail by hand is difficult. Although rhizomes growing near the surface can be forked out, deeper roots will require a lot of excavation. Shallow, occasional weeding is not effective and can make the problem worse, as the plant can regrow from any small pieces left behind. However, removing shoots as soon as they appear above the ground can reduce infestation if carried out over a number of years.

Nettles

Urtica dioica 

Thistles

Sonchus asper 


Cleavers

Galium aparine 

Fat Hen

Chenopodium album 

Groundsel

Senecio vulgaris 

Produces seeds all year round. Although hoeing seedlings is effective, remove the larger uprooted plants as these can still set seeds that germinate. Seeds spread on the wind, but only last a few years in the soil. 

Ash

Vietnamese Coriander