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Living with Perennial Weeds

Is there any gardener who hasn’t got, or had in the past, a problem with perennial weeds?  Even the smallest garden can be beset with couch grass and dandelions galore, with ground elder or creeping thistle invading every border.  In fact in a small garden in a terrace with gardens on either side (that may not be well cared for), the problem can be a nightmare.  These plants can spread through from neighbouring gardens on either side regardless of monumental efforts to keep them out.  How do we deal with these thugs?  Can we eliminate them, or do we need to learn how to cope with them and even appreciate their tenacity?  And it is always worth remembering that your worst weed nightmare could be a wildlife magnet in disguise.  However I feel about the more ‘weedy’ plants in my garden that cause me problems, I also have to admire them.  To be successful, to reproduce and spread and occupy a suitable habitat, is what a plant is designed to do.  And sometimes it is our interference that has contributed to the problem, perhaps the addition of too much fertiliser, the removal of other plants that then allow it free reign or even the elimination of its natural predators that might have helped to keep it in check.  In some situations we may need to learn to live with a perennial problem rather than spend all our time trying to fight it tooth and nail.

To the new gardener or allotment holder, the sight of a plot brimming over with nettles or couch (called squitch in my home county of Oxfordshire) is a daunting sight to say the least.  But in some ways this is the best situation to be in – here at the very start of your gardening journey you can generally make a real impact on any major problems before you have planned and planted.  And if time is on your side, especially where transient vegetables crops are concerned, it is possible to severely reduce or even eliminate perennial weeds.  Simply covering your plot with something that excludes light for a time (black plastic sheeting, old carpet or a specialist membrane) can be effective.  Going down this route certainly gives you the upper hand as once the majority of the offending plants have gone the remnants may be dug out more easily.  I often take this approach in my garden, especially with nettles and docks although the latter with their deep tap roots are incredibly tenacious.  I generally use grass cuttings or the hay from my meadow areas rather than plastic or carpet which I find very ugly. These materials can also flap about if left through the winter (or sometimes blow away completely in my windy garden!).  Piling cuttings really thickly onto an area of nettles, docks, creeping buttercup and unwanted grass and other weeds, especially if left from autumn to spring, can very effectively kill off the majority of these plants and loosen the soil underneath to such an extent that digging out the remaining few roots will be a pleasure rather than a chore. 

This method will also help to enrich the soil beneath with nutrients from the break down of the organic matter attracting earthworms and other soil invertebrates.  I have recently employed this technique on an area of rough grass and weeds where I intend to make a new pond – now easy to dig and no turf to remove.  It also provided a winter habitat for voles – the decaying hay is riddled with the runs of bank and field voles which provide food for the local tawny owl, fox and kestrel. 

Digging of course is the option many organic gardeners choose to take.  In a small area this is entirely effective as long as one is meticulous.  It is also essential to dispose of the roots and rhizomes in such a way as to ensure they don’t get the chance to grow and spread.  I tend not to compost roots of this kind, unless it is mid summer and they can first be left in the sun to dry out completely.  I put them into my green wheelie bin (which otherwise remains empty all year round) from where they make their way to the local biowaste digester.  Like so many gardeners, I seem to have spent my entire gardening life trying to deal with certain perennial weeds, in particular nettles (on my first ever allotment) couch grass and horsetail (my previous garden) and ground elder and bindweed in my current garden.  But whatever perennial weeds we have in our plots and however we deal with them, they always have some value however obscure.  Every one of these difficult plants has wildlife value of some sort, whether it be as a pollen or nectar provider, a larval food plant of moth, butterfly or other useful insect, a seed provider for birds and small mammals or simply as a plant in which to hide and shelter.  It is worth remembering that in any garden, as far as your local wildlife is concerned, any plant is better than no plant at all.  A weed is in the eye of the beholder - one gardener’s nightmare could be another’s favourite wildlife attractant.

 The bad guys – the worst four to look out for:

 Couch – Elytrigia  repens  (Agropyron repens)

Couch, Twitch or Squitch – this plant has plenty of local names reflecting its widespread distribution.  It loves newly dug soil and will rampage through all types (including the heaviest clay) in what seems like a matter of days.  The rhizomes have a fiercely pointed tip which have been known to grow through potatoes, concrete and even golf balls!   Covering will kill off the immediate plants but of course the rhizomes emerge unscathed and head off through beds, borders and lawns with abandon.   Best dug out where possible.

Plus points – this grass is used by a wide range of moths and some butterflies as a larval food plant. 

Ground elder – Aegopodium podagraria

Jump About was one of the common names for this plant and if you have this species in your garden you will know why!  It spreads easily from place to place and is perfectly happy in very poor soil.  It was introduced in the Middle Ages as a cure for gout.  If ground elder had pink or purple flowers we would probably all be growing it in difficult spots as ground cover as its white flowers (it is a member of the carrot family and the flowers resemble a smaller version of cow parsley) are actually very pretty.  The leaves are also quite attractive but the spreading nature of the roots means that it gets in amongst other plants and is very difficult to remove.  There is a less invasive cream variegated variety of this plant that is sometimes grown as ground cover.

Plus points – the leaves make a tasty alternative to spinach and some moth species use it as a larval food plant.

 Horsetail – Equisetum arvense

This plant is generally thought of as a species that is a problem in wet soils but this is not strictly the case.  It likes to grow in compacted and poorly drained soils and plagued my previous garden which was on a sandy soil.  Like couch and ground elder it is a plant that spreads rapidly underground by dark rhizomes, but this species has a trick up its sleeve – the roots can happily grow and spread at depths of one meter or more, making it virtually impossible to remove by digging.  It is an ancient plant related to the ferns and reproduces by spores, so we do not even have the benefit of flowers of any kind!

Plus points – sadly there are few but the stems have been used in the past to scour pots and pans plus it is used as a medicinal herb as a diuretic.  Recent research has focused on its use in the treatment of osteoporosis.  It does produce thick ground cover for wildlife.

Nettles – Urtica dioica

This familiar perennial weed is less of a problem to cope with than some others.  Generally nettles can be dug out fairly easily – their fibrous root systems interconnect and digging them can be very satisfying.  Nettles prefer a soil rich in nitrogen so in a new garden or allotment can be indicators of good fertile soil.  In grassy areas nettles rarely survive repeated mowing which is one way of eliminating them.

Plus points - nettles of course are the larval food plant of the caterpillars of small tortoiseshell, peacock and red admiral butterflies and many other small beneficial invertebrates thrive on them including ladybirds.  In the garden they are generally only used by butterflies if they are in warm sunny spots. 

Other aggressive but wildlife friendly perennials include:

Bindweed, dock, creeping thistle, dandelion, creeping buttercup and bramble.