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The war on weeds

27 June 2023
Pull out as much of the root system as you can.
Pull out as much of the root system as you can.

Here are 10 easy ways to tackle the battle organically.
WORDS & PHOTOS Mark Rayner

It’s one of those jobs that never seem to end ‒ the constant battle to keep your garden free of weeds. And although the first response might be to reach for a chemical solution, there are many less toxic ways to win the war on weeds. Here are 10 practical ideas to organically eradicate those pesky invaders as well as keep weeding to a minimum on an ongoing basis.

Cover them up

Like all plants, weeds need sunlight to photosynthesise and grow, so by depriving them of light for an extended period they will, over time, surrender and expire. Thick black polythene is ideal for this – just cover the weed-infested area and weight the plastic down with bricks or large stones and then leave it for up to six months. If done over summer, the solar heat generated by the sun will help further by ‘cooking’ the offenders. This method can be used on all manner of unwanted plants ‒ I once successfully eradicated a particularly large (and stubborn) clump of bamboo in this way. The upside is that it’s effective, inexpensive and easy to carry out but the downside is the wait and the ‘all-or-nothing’ nature – no good if there are existing plants you want to keep among the weeds.

Mulch, mulch, mulch

Similarly, mulching the soil around plants also blocks out light making it harder for weeds to get a stronghold. Even better is to put a thick layer of cardboard or newspaper down first and then cover this with a very generous layer of mulch. If it’s in a vegetable garden or one with a range of seasonal plants and flowers use a mulch which will break down over time and help to feed the soil – well rotted compost, pea straw and shredded wood chips are all good for this. Keep topping up the mulch as necessary, even using the popular ‘chop and drop’ method to cut down plants as they fade to add to the layer of green matter protecting the ground around them.

Pull them out

If you decide to face the enemy head on and physically remove the offenders, then try to remove as much of the root system as possible to prevent regrowth and avoid overly disturbing the soil as this may bring dormant weed seeds to the surface. Use a garden fork or trowel to loosen the soil around the base of the weeds and then gently pull to keep the roots intact. It also helps to know your weeds – which ones have strong taproots (dandelions), pernicious bulbs (onion weed) and rampant runners (creeping buttercup).

Go with gravel

Another popular method to reduce weeding is to create a gravel garden where suitable plants can thrive and weeds are kept to a minimum. Again, it’s going to be necessary to cover the existing soil with a permeable barrier first – you can use weed mat but I prefer thick layers of cardboard or newspaper – and then cover this with a layer of pea metal (at least 10cm deep). Weeds will, over time, pop up, but these are most likely to be self-seeded so perfectly manageable if ‘nipped in the bud’.

Feed the soil

It’s a weed’s job to help mother nature by improving inhospitable or nutrient-deficient soil so it makes perfect sense to understand that weed seeds are less likely to germinate in healthy soil. To this end, keep feeding your soil with a generous ongoing supply of good compost or rich organic matter (spent coffee grounds, uncooked kitchen waste, lawn clippings, sawdust from untreated timber etc). Avoid disturbing the soil and, more importantly, the beneficial micro-organisms working hard below ground.

Watch where you water

Again, remember that weeds are no different to other plants and will thank you profusely for a regular drink, so avoid indiscriminate watering with a general sprinkler or spray system ‒ try instead to target only those plants you wish to cultivate. A soaker hose or drip-fed irrigation system will help to direct water to the plants that matter, hopefully leaving the weeds thirsty. This will also reduce the amount of water used – a win, win.

Crowd them out

Where possible, mass plant with a selection of low-maintenance beauties to shade the surrounding soil and limit competition from weeds. Try to avoid very low-growing ground cover plants as enemy grass seeds may still germinate and grow frustratingly through them. Opt for evergreens (which will provide year-round cover) and consider the growth habit and size of the plants – a rounded, medium-sized shrub with a dense canopy will shade the surrounding ground more than one with an upright habit and light and airy foliage.

Chop chop

We’ve all heard the old gardening adage ‘One year’s seeds, seven years weeds’ and so if there’s any truth to this then it’s best to act early. If you aren’t able to actually physically remove the whole weed, then some judicious deadheading before seeds set will help to prevent annual and perennial weeds from multiplying. Similarly, a drastic slash through a patch of weeds with a weed-eater may not eradicate them completely but it will certainly give them a shock and (hopefully) lessen their hold. Done on a regular basis, some weeds will almost certainly give up the fight.

Watch the weather

Your approach to the attack on the enemy weed may differ depending on the time of year and weather conditions. After a spell of heavy rain when the soil is wet it’s best to pull weeds out in their entirety but in hot and dry conditions it can be just as effective to slice weeds off just below the soil level using a sharp hoe. Choose a really hot day when the sun is blistering down and these little chopped-off horrors will soon shrivel up and die.

No digging allowed!

There are likely to be thousands (maybe millions?) of ungerminated weed seeds lurking below ground in your garden and every one of them is just waiting for the day you push a spade into the soil and bring them (and all their relatives) up to the surface where they will happily take over. As weed seeds can remain viable for many years it makes sense to ‘let sleeping seeds lie’, leaving the soil undisturbed, and simply improving soil structure with continuous mulching with good organic materials such as well-rotted compost or brown leaf mulch.

Read more from Mark, on greener gardening and landscaping, in every issue of Kiwi Gardener.

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