People always tell you weeds are only wildflowers growing in the wrong place. All I can say is there are some pretty notorious wildflowers whose main goal in life is to invade the garden and swamp everything. It is a constant battle, but if you want to win the war, you have to understand the enemy. Most of the weeds in my garden are fortunately constrained to the flower borders as the lawn is completely weed free – not down to me though, just the fact that it’s an artificial grass lawn.
These are the harmless end of the weed spectrum. They include things like groundsel, shepherd’s purse, chickweed and fat hen that spread themselves around by seed. They grow, flower, set seed and die all in the same season and are the easiest weeds to control, as once you pull them up or hoe them out they do not re-grow. Provided you don’t wait until they have set seed, you can put them on the compost heap quite safely. Alternatively spray annual weeds with a contact weedkiller containing paraquat, which acts like chemical hoeing, but take care not to get it on any nearby plants.
These are nettles, thistles, docks and suchlike. This group behaves rather like herbaceous perennials. The tops die down each autumn, leaving dormant roots underground from which a new crown emerges next spring. If you catch them young enough, they are not too bad to deal with. You can just dig them up and that is probably the last you will see of them. However, a big, old clump can be harder to shift, as it will often start spreading out sideways too, so you cannot be sure of getting the lot out. And when perennial weeds grow up through the middle of cultivated plants (which they have a great knack of doing), they are almost impossible to remove unless you dig up the plant and carefully separate out the good and bad roots.
Some perennial weeds are not just a nuisance, but more of an epidemic in the offing. These are the stranglers and fast spreaders, like bindweed, horsetail, ground elder and couch grass. They are notorious for their thick, white, underground roots which grow to great depths, making it impossible to dig them out.
Spot treating with a glyphosate based weedkiller or hoeing thoroughly every time new shoots appear above ground will get rid of them in time.
Eradication by Hand
Although it sounds very simple, there is absolutely nothing you cannot kill in time if you keep hoeing it – even nasty perennial weeds cannot survive being constantly chopped off at ground level. The secret of successful hoeing is do it while weeds are small. Choose a sunny day, so that weed seedlings wither straight away, then you don’t even need to rake them up and get rid of them.
It is better to weed by hand when the ground is moist as the weeds will come out more easily. Gather them up and compost them afterwards. Do avoid putting thick-rooted weeds on the compost heap, though, as they might survive the rotting process.
Where perennial weeds are growing in between plants in a border, it is usually possible to spot treat them individually with weedkiller. Choose a glyphosate-based weedkiller, which will be taken in through the leaves to kill the roots as well as the tops. Either buy a gel formulation and paint it carefully on to the weed leaves, or use a ready mixed formulation in its own sprayer bottle. Shield nearby plants you don’t get any weedkiller on them.
Very persistent weeds may need several applications. Big, old perennial weeds, whose leaves are tough and fairly resistant to weedkiller, are best treated by cutting the stems down and then treating the soft, new growth that follows, which is much more susceptible. You will probably need to re-treat the same clump several times.
In some situations you can use special weedkillers that prevent any weeds from growing at all. Use path weedkillers on paths, gravel drives and cracks between paving stones. They kill existing weeds and stop any more coming up for the rest of the season.
Total weedkillers containing sodium chlorate need using very cautiously as they stop anything growing for a long time – often several years. However, unlike path weedkillers, they can often spread sideways in the soil. I prefer not to use sodium chlorate at all.
Weedkiller with the active ingredient dichlobenil stops both annual and perennial weeds growing for a full season, but must be sprinkled over weed-free soil in early spring. It can be used under only established trees and shrubs, not where there are bulbs, perennials or where you will want to plant annuals.