Bindweed, couch grass and ground elder often embed themselves in borders, shrubs and hedges, where they are brilliantly adapted to persist, despite the best efforts of gardeners. They have spent the summer extending their roots and will now be filling those roots with food before they die back for the winter, so they can regrow in spring with renewed vigour. Gardeners aim to prevent this.
Couch grass has long-spreading underground rhizomes – underground stems – that spread, eventually forming a thick mat.
Couch grass does no harm in lawns or meadows and supports the caterpillars of some moths and butterflies. It dies out in closely mown well-fed lawns, but it can be a nuisance in vegetable gardens and among perennial plants such as soft fruit, shrubs and herbaceous borders.
Bentgrass has a similar habit but with above-ground rhizomes which makes it easier to clear but it can still be a difficult weed. Each rhizome has buds along its length that can send up leaves or give rise to new rhizomes.
Bindweed comes in two main forms, field bindweed and hedge bindweed, the latter being the main garden problem. Its roots go deep and its climbing stems clamber over even large shrubs and hedges.
Its white-and-pink trumpet flowers and deep green heart-shaped leaves are pretty and it benefits wildlife, so it is an asset to wild places and covers eyesores such as chain-link fences and is much loved by many people – though by few gardeners. It is relatively easily seen and pulled off other plants and cut to ground level, which weakens it and slows its spread.
Ground elder also has a very invasive root system, extending as much as 90cm per year, allowing it to expand into beds and borders.
On the plus side, it supports a wide range of insects, not least by its delicate white umbels of flowers.
Bindweed colonising old rubble pile (Photo: Tim Sandall/RHS)
It is a shade-tolerant woodland plant and in many situations – beneath hedges, for example – it can be considered useful ground cover where little else will grow. This is just as well, as it is almost impossible to eradicate from such situations.
These, and other perennial weeds, produce an underground “bud bank”. These dormant buds allow the plant to regrow even if you remove the foliage.
In theory, if you cut back or hoe often enough, perennial weeds will be weakened and even die. In practice, the best that can be achieved is to slow the spread of the weed. However, seeds – another way these weeds spread – will be prevented.
More effective countermeasures include digging out in veg plots where these weeds are seldom serious.
In other areas, they can be winkled out with a fork, although this is much less effective on deep-rooted bindweed, as any fragments left behind will form new plants from dormant buds. These have to be mopped up subsequently by lifting the new weed with a trowel or border spade.
Smothering with a mulch such as woodchips over several layers of cardboard is possible, especially in shrub or soft fruit areas. Clearing beds and borders and sowing them to lawn seed works well, as most perennial weeds cannot survive mowing.
Clearing herbaceous plants including strawberries and leaving for a year to dig out any remaining bindweed is a drastic but thorough option. Pot up valued plants to be saved after eliminating any bindweed roots – washing the rootball in water can help. Replant these once beds and borders are perennially weed-free.
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