How to win the war on weeds

How to win the war on weeds

If you let weeds gain a foothold, you’ll have trouble for months and even years to come, but to gain control and win the war against weeds you will need to get to know your enemy. The commonest weeds in your garden are not necessarily the ones you should worry about most. These are generally annuals that seed themselves about covering every square inch of vacant ground if you let them. Although annoying and time-consuming to deal with, they are generally innocuous and easy to control. The most troublesome weeds are much less obvious - spreading throughout beds and borders via underground stems and roots. Invariably perennial, they die down in winter, to rise again with increased vigour each spring. A few are real monsters – invading borders and swamping ornamental plants …and can become a serious problem because they don’t respond to the usual methods of weed control.

Some golden rules

  • Act quickly. Tackle weeds as soon as they are noticed, preferably when they are still seedlings. Never let weeds flower and set seed.
  • Take steps to prevent weeds in the first place by covering vacant ground with mulches and groundcover plants.
  • If you must use chemicals then use a glyphosate-based systemic weedkiller to tackle problem perennial weeds and to prevent them re-growing from scraps of root and stem left in the soil.
  • Consign the roots of perennial weeds and any weeds that have set seed to the dustbin because if added to the compost heap you risk transferring them around the garden along with your compost.
  • If time is short and you don’t have time to weed properly, make sure you remove flowering weeds first to prevent them setting seed.

Know your enemy

Which weeds prove to be troublesome in your garden will depend on where you live, your soil and how you go about controlling them. In my Hampshire garden, ground elder can be a real pain, but by regular forking I’ve managed to keep on top of it. Some weed problems are quite localised. For example, I’m plagued by acorns carefully planted by squirrels each autumn and then conveniently forgotten about, so each spring tree seedlings can pop up almost anywhere – even in my permanent containers! Even an oak tree can be a weed if it’s growing in the wrong place.

Top six annual weeds

Chickweed (Stellaria media) Hoe or hand weed and pick up the seedlings. Forms a low-spreading carpet once established with horizontal stems rooting as they grow. Seeds are very long lived in the soil.

Cleavers (Galium aparine) Hoe or hand weed when young. Once established, the ‘sticky’ stemmed plants are difficult to untangle from border plants and the seeds will attach themselves to your clothing to be transported around the garden.

Fat hen (Chenopodium album) Hoe or hand weed as soon as they are seen. Young plants can set seed within weeks, showering the soil with seeds.

Groundsel (Senecio vulgaris) Hoe or hand weed on a warm day. Quick growing, they produce several generations each year – even during mild spells in winter!

Hairy bitter cress (Cardamine hirsuta) Hoe or hand weed as soon as possible since they are very quick to mature and set seed - flinging their seed from spring-loaded seedpods.

Red dead nettle (Lamium purpureum) Hoe or hand weed the nettle-like seedlings which appear in flushes during spring and autumn. Reaches 15cm (6in) before it flowers.

Top six perennial weeds

Creeping buttercup (Ranunculus repens) Hoe or hand weed this low-growing buttercup. One plant can spread to cover over 4sq metres in a single year and the seeds are very long lived. Dig out established weeds by hand.

Creeping thistle (Cirsium arvense) Although a prickly devil when mature, as a seedling it’s easy to deal with by hoeing or hand weeding. Never let it set seed! Use a systemic weedkiller as a last resort.

Dandelion (Taraxacum officinale) Hoe seedlings in spring, dig out established weeds by hand, taking care to remove the whole taproot, any portion of which will re-grow if left. Never let it set seed!

Dock (Rumex obtusifolius) Hoe or hand weed as seedlings in spring, dig out established weeds by hand, taking care to remove the whole taproot any portion of which will re-grow if left.

Greater bindweed (Calystegia silvatica) Hoe or hand weed seedling flushes that appear in spring and autumn. Bindweed becomes a problem once established because its insidious twining stems will smother border plants. Digging up established weeds will weaken the plant, but any scraps of root left behind will re-grow. In severe cases use a systemic weedkiller. Unwind as many bindweed stems you can and push them into a polythene bag before applying the weedkiller. This not only ensures a good coverage, but also protects nearby ornamental plants.

Stinging nettle (Urtica dioica) Hoe or pull up young seedlings when they appear in spring or autumn. Older plants are fairly easy to dig up too…provided you wear gloves!

Top six problem weeds

Bramble (Rubus fruticosus) Brambles are easy to hand weed when young, but get big and mean once established. They are very deep rooting and you’ll need thorn-proof body armour before you can really get to grips with them. If you’re brave, you can cut them down with secateurs or loppers, or you might like to hire a brush cutter or Allen scythe to remove all the top-growth from very large clumps. Pile up the stems on the top of the weed’s roots and, once dried to a crisp light the prunings to burn off any new emerging shoots that have subsequently appeared. Thereafter, cut off any new shoots that emerge for the rest of the growing season, before setting about lifting the much-weakened clump in autumn. As a last resort, brambles can be tackled by repeat applications of a systemic weedkiller, but you’ll still have to remove and dispose of the remains.

Couch grass (Elytrigia repens) Seedlings can be tackled easily enough by hoeing in late spring and early summer. Dig out established weeds by hand, taking care to remove all the wiry root-like creeping rhizomes which will regrow. These can reach several metres long so be painstaking about it. If growing in established beds, it’s best to lift all the plants in the bed and carefully tease out all the weed roots from each plant you want to keep. Couch grass can be controlled by systemic weedkiller, but take care to protect nearby ornamental plants.

Ground elder (Aegopodium podagraria) A perennial with elder-like leaves that spreads and spreads and spreads if you let it. Once established, it forms a dense knee-high blanket of foliage that smothers all neighboring plants as it grows. It’s near impossible to dig out because the soil is filled with roots that will regrow if any scrap is left. Constantly cutting back can weaken it over time, but it will take several years and a lot of hard work. As a last resort, use a systemic weedkiller and reapply as necessary.

Giant hogweed (Heracleum mantegazzianum) Take great care when tackling this architectural monster, its sap is a serious irritant to the skin in sunlight and can produce a very nasty reaction including huge blisters. Always cover your arms and legs, as well as wearing a protective visor over your face before dealing with this weed. In fact, I’d recommend that you don’t touch it until the winter when there’s far less risk from the irritant sap. Then burn the woody stems back using a flame gun and dig up the weakened roots.

Horsetail (Equisetum arvense) The bane of many who garden on damp soil. It is incredibly deep rooting (reaching down several metres!) so digging it out is impossible. You can weaken it into submission on ornamental beds by regular hoeing and on vacant ground by regularly running over it with a nylon-line trimmer or rotary mower with the blades set high. Weed-proof mulches can also work, but it may take several years before you can remove them. As a last resort, use a systemic weedkiller after crushing the waxy stems so they take up the chemical more readily, and reapply in subsequent years as necessary.

Japanese knotweed (Fallopia japonica) A weed of monstrous proportions. It can form huge clumps that will eventually take over your entire garden (including your drive and patio!). Spotted early it can be dug out, but once established you’ll be at battle stations for years. It’s very deep rooting so digging it out is impractical. If you’re unlucky enough to have this weed you may be able to weaken it by constantly cutting off its top-growth. Don’t let it produce more than one or two leaves on each new shoot otherwise this method won’t work. As a last resort – and with this weed maybe the only solution – is to spray it with a systemic weedkiller, but even then it may take several applications over several years to rid your garden of this persistent weed completely. Good luck!

Weedkiller advice

If you have to resort to using a chemical weedkiller, make sure of the following:

  • Choose the right weedkiller for the weed you are trying to kill, taking into consideration its situation and the surrounding plants.
  • Follow the guidelines on the packet to the letter. Never use weedkillers at a ‘stronger’ dilution than that recommended on the packet.
  • Apply weedkillers just before the weeds are ready to flower. This not only prevents them setting seed, but it is when the weeds are at their most vulnerable.
  • Apply the weedkiller accurately, taking care not to get it on nearby ornamental plants.
  • Choose a dry, still day to apply weedkillers. If it rains soon after application, much of the chemical will be washed off.

Controlling weeds around the garden

The best way to set about tackling weed problems will also depend on where in the garden the weeds appear.

Cultivated areas. Weeds should be easy to tackle because they will not have had time to establish. Seedlings can be controlled by hoeing between crops on the vegetable patch. Choose a warm, dry day so that the hoed weeds soon shrivel and die. If there are weeds that have flowered, carefully pull these out by hand to prevent them scattering seed on the soil. Also hand weed between plants in the row. Prevent weeds by laying down organic and fabric mulches between rows.

Lawns. Few weeds can survive constant mowing and the competition form vigorous lawn grasses. However, if the lawn is not growing strongly or is damaged by heavy wear, weeds can become established. Individual weeds can be dug out by hand using an old kitchen knife or treated with a dab-on lawn weedkiller. If the problem is more widespread, treat the whole lawn with a special lawn weed & feed or weed, feed & mosskiller – depending upon the problem weeds you have.

Paths and patios. An old kitchen knife or a special weeding tool will be the best option for removing individual weeds from between paving stones. Alternatively use a dab-on weed treatment. Patches of weeds in gravel can be controlled early on by hoeing or treated with a path weedkiller that will also prevent new weed seedlings from germinating for up to a year. Prevent weeds between paving stones by either filling the gaps with mortar or tough, low-growing ornamental plants, such as thyme.

Beds and borders. Hoeing and hand weeding will control most weeds if they are caught early. You could also use a dab-on weed treatment for individual established weeds. Some perennial weeds, such as couch grass, that will re-grow from every piece of root and stem left in the soil may require more drastic action. In this case you may have to lift the entire bed of plants and painstakingly collect every scrap of weed root in the soil as well as teasing out the weed roots from those of the ornamental plants. Alternatively, use a systemic weedkiller on rapidly growing weed shoots, carefully avoiding the ornamental plants. Either cover the plants with polythene before you spray or push the shoots of the weeds into a polythene bag and apply the weedkiller there. Do not remove the polythene until the spray has completely dried. Prevent new weed seeds from germinating by applying a 5-7cm (2-3in) deep organic mulch, such as composted bark, over the entire bed.

Shrubberies. If you have perennials or bulbs growing among the shrubs you will have to follow the advice for ‘Beds and borders’, above. However, if you have shrubberies filled with established woody plants only, you can consider putting down a fabric much such as mulch matting or old carpet. If you don’t mind using chemicals, you could also consider applying a dichlobenil- based weed preventer that inhibits weed seeds germinating in the top few centimeters of the soil provided it is not disturbed.

On vacant ground. Hoe and hand weed regularly to control weeds when young. Alternatively smother them with thick black polythene or old carpet. A common mistake made by a lot of new gardeners is to hire a rotavator to clear a weedy garden. Far from controlling perennial weeds, such as couch grass and ground elder, it chops up the roots -each piece of which will grow into a new weed - and actually increases their numbers.

Neglected areas. Established clumps of woody perennial weeds can be cut back using a brush cutter or Allen scythe or burned with a flame gun, and then the roots dug up. If digging the whole area sounds too much like hard work and you’re not in too much of a hurry, old carpet or thick black polythene will smother any re-growth – killing the weeds roots in just a few years! Another option is to treat the re-growth with a glyphosate-based weedkiller. But even this may take several attempts over months or even a couple of years for very persistent weeds. I wouldn’t recommend you use more toxic chemicals, such as sodium chlorate, because it moves sideways in the soil, persists for a long time and you will have to wait for at least six weeks before the ground can be planted.

Oh, and don’t forget to keep your hoe sharp at all times!