WITHOUT doubt, the most effective means of controlling weeds — without using toxic sprays — is to use useful, more aggressive plants to suppress them.
In an ornamental garden, these include most dense, ground-hugging perennials, shrubs, prostrate conifers or small trees.
Even dome-shaped shrubs with large, overlapping, light-excluding leaves such as “oak-leaf” hydrangea (H. quercifolia), large-leaved rhododendrons and even Philadelphus (Mock Orange).
All these attractive ornamentals eventually develop such tight, intact canopies that even aggressive weeds cannot survive beneath them due to lack of light.
In the vegetable garden, it’s a different story because few plants are permanent and the ground is regularly cultivated.
Weeds are great survivors. If uncontrolled, they compete relentlessly and successfully for nutrients, moisture and light. Sadly, they are always with us.
Some weeds develop extra-deep roots so are able to tolerate long, dry periods by tapping into moisture deep within the subsoil.
They are highly effective at stealing nutrients from the vegetables we try to grow, usually germinating well before the seeds we have sown and rapidly becoming established first.
In fact, many weeds produce substances that can restrict the growth of other adjoining plants.
Despite the vigour and persistence of weeds, it is still possible to gain good control without any need for disruptive herbicides. Best of all, we can use many common vegetables to keep weeds suppressed.
My own methods are simple. Before sowing vegetable seeds I thoroughly cultivate the soil and after raking and levelling the surface give the bed a good soaking. Within a few days the first weed seedlings appear. I use a mechanical hoe or a light shuffle (Dutch-type) hoe to disturb, expose and destroy the tiny weeds.
After about 10 days, all weed seeds close to the surface will have germinated and been destroyed.
This allows seeds of the most vulnerable vegetable varieties (carrot, parsnip, beetroot, onion) to be sown without any need for the soil to be further cultivated.
They then germinate and come up thickly with little weed competition.
Once a root-crop bed has developed, the dense covering of foliage effectively restricts the growth of any weed seedlings that may appear later.
I’ve long used close-planted brassica and other leaf crops to keep weeds suppressed.
Planting cabbage, cauliflower, broccoli, kale, silverbeet and even lettuces fairly close together produces a remarkably intact leaf canopy.
This also allows useful thinnings to be harvested as young plants are developing. Most slightly immature brassica seedlings make highly nutritious, tasty eating.
In Britain and Europe, these thinnings are carefully gathered from late winter onwards to be placed on sale as “spring greens”. They are very much in demand.
Perhaps the most effective and easily grown of all edible weed suppressing plants are potatoes.
Most experienced gardeners and farmers have long used potato crops — with their floppy, spreading foliage — as an effective means of “cleaning up” weed-infested ground.
Once healthy crops begin growing strongly, it is impossible to see the soil because of the dense mass of entangled shoots and leaves.
Last winter, I grew a particularly vigorous crop of English spinach. The seeds were sown directly into soil enriched with biochar in March.
The result was a magnificent ground cover composed of enormous leaves that completely covered all parts of the soil.
Not one weed was able to get through to the light and survive.
The same bed is now once more fully covered, this time with root vegetables in full leaf and, once again, all weeds are completely controlled.
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