The art of keeping a garden free of weeds
12:52 22 May 2015
Roddy Llewellyn explains why weeds can become boring guests that refuse to leave your garden, and how best to deal with them
The dictionary definition of a weed is “any plant growing where it is not wanted by man”. It is interesting, therefore, that any ornamental plant that self-seeds in unwanted placed becomes a ‘weed’. If we choose to accept that derogatory definition, I can think of several plants regularly entertained in Gold Medal-winning gardens at Chelsea Flower Show to qualify in this category. These include Verbena bonariensis, Stipa tenuissina, lily-of-the-valley and Cerinthe major ‘Purpurascens’. They are constantly popping up in rather inconvenient places, like in the centre of a path, but even the most discerning of gardeners will leave them in peace. This, presumably, is when a weed becomes a friend.
But then there are several other weeds whose offspring are never greeted with pleasure when they appear especially in the vegetable garden. If you find them a constant source of irritation it is normally because you have a garden that has been badly neglected in the past. Weed seeds have an aggravating habit of remaining viable in the soil for 20 years or more, so even if you think you are doing good by digging the border, what you could also be doing is to bring those seeds closer to the warmth of the soil surface resulting in a new army of uninvited, boring guests with bad manners.
The art of keeping a garden free of weeds is to deal with them good and proper at the very beginning of the growing season like NOW, your best ally being your hoe. It is a frightening though that one weed can produce hundreds if not thousands of seeds. It is important to get rid of those particularly tiresome weeds like groundsel and speedwell that self-seed in the blink of an eye even during mild spells in the winter. Sometimes I don kneepads so that I can get close in to the action, a must if weed seedlings have popped up in the middle of herbaceous perennials. In this secular age us gardeners are some of the last to genuflect, although there is little worship included in this humble posture.
The worst thing you can do to a perennial weed like thistle, dock, bindweed, ground elder, couch grass and dandelion is to hoe them or run a rotavator over them because all you succeed in doing is to chop up their roots and as a result increase their numbers. Only recently I was asked over to advise on a serious infestation of perennial weeds in a recently restored kitchen garden, and without one second of doubt I recommended spraying the entire area with a glyphosate-based product (sold under trade names like ‘Roundup’) in late spring when these weeds are growing hard and fast. Always spray on a dry day.
The person I was advising was nervous about using this product and I told him that while there do exist a number of weed-killers with harmful side effects, glyphosate does become inert within minutes of reaching the soil. Moreover, it is safe to plant or sow in that same ground soon after it has been sprayed. However this product must be sprayed, just dampening the leaves, on a still day to prevent ‘drift’ from landing on leaves of wanted plants. You will need to wait for about three weeks after spraying for the weeds to start dying. If you have an established perennial weed growing in the middle of, say, precious herbaceous perennials you are better of dabbing its leaves with a gel that is easily brushed on.
If you don’t want to use any chemical at all and you’re not in any rush you can easily kill all your weeds by covering the entire area with opaque black plastic (weighted down to stop it from blowing away) which you leave for one entire year by which time every single of weed should have been, quite literally, smothered to death in the absence of any light.
Dig the area the following spring and plant it up with crops like potatoes brassicas and beans whose cultivation helps to clean the soil. You will need to be disciplined and hoe all weed seeds as they appear. A similar method is used for getting rid of weeds like ground elder which can be covered in a thick (minimun 6”/15cm) mulch of farm yard manure. This succeeds in making the plants form their roots far closer to the soil surface and therefore much easier to dig up. The acquisition of farm yard manure, however, may prove impractical.