Perennial Weeds
Working today to eradicate couch grass – know as “twitch” up north – from a client’s garden. Like all perennial weeds, couch grass has evolved to store food in its roots during the growing season which then enables it to regrow from these underground reserves in the spring. This also means that if you leave even relatively small sections of root in the ground whilst weeding, the damn thing will almost certainly regrow…
So what’s to be done? There are three basic options:
- Spraying with weedkiller. Not an option if you prefer to garden organically, nor if the weeds are growing amongst other plants that you want to keep, as is the case with my client where the couch grass has taken over one end of a shrub border
- Smothering with a weed proof covering. Woven plastic membranes are available commercially, or you can recycle cardboard packaging or similar: Both methods work by eliminating light from the weeds, thus they can’t photosynthesise. Eventually the weeds use up the reserves of energy in their roots and die off, but this will take a minimum of several months and potentially a year or more dependent upon the type of weeds and the size of the root system that they have been able to develop. Whilst this is a good way of clearing perennial weeds from an open area such as an overgrown allotment, for example, the downsides are that the area is going to look somewhat unattractive for the duration, and it’s also often not a practicable option where the weeds are growing amongst other plants that you want to keep
- So I’m left with digging it out…
Realistically, you are never going to get it all out first time; some root will inevitably be left in the ground and it will regrow. However, if you can then get these regrowths out as soon as they poke their horrid heads above ground, they will have had very little time to photosynthesise and you will quite quickly deplete their energy stores, thus killing them off. So be as thorough with your weeding as you can first time through, then revisit every few days to get out any regrowth…
One difficulty can be where, as is the case with my client’s shrub border, the weeds’ roots are entwined with those of a plant you wish to keep. Here the only viable option is to dig out the wanted plant and carefully tease out the weed roots from those of the wanted plant. DO NOT do this on a hot and/or windy day as the fine feeder roots of the wanted plant will suffer; this morning was relatively cool, still and humid here in the Cotswolds, plus heavy overnight rain meant that the plants were fully hydrated, so the stress to the wanted plants was minimal. That said, put the wanted plants back in the ground as quickly as possible and then water copiously. Fortunately the soil at my clients’ garden is a fine alluvial loam, so this technique is quite straightforward. On heavier clay soils, less so…
For larger trees and shrubs, where digging the wanted plant out isn’t practicable, then smothering is your only viable option. I’d suggest using old cardboard and covering that with several inches of compost or bark mulch to hide the cardboard, which will rot down after a few months by when (with luck) the underlying weeds will have died off…
Good luck!!!
