Methods for Controlling Weeds

Controlling Weeds

Dig out perennial weeds during deep cultivation and attack annual weeds with a hoe.

Use chemicals only in dire cases.

Weeds must be controlled in the garden for a number of important reasons. Obviously, they are unsightly, especially among flower beds and borders, but they also threaten the health and vigour of cultivated plants. During hot spells they compete for valuable water, and, throughout the year, tap nutrients and shade out sunlight. Many weeds also harbour pests and diseases which can easily spread to ornamental plants and food crops.

The old saying ‘one year seeding means seven years weeding’ is very apt. Both annual and perennial weeds, if left uncontrolled, shed seeds which often germinate when conditions suit — particularly when brought to the surface by soil cultivation. Many even flourish during cold weather, when other plants lie dormant.

Never allow weeds to flower and produce seed, even though some, such as the red deadnettle, dandelion, field speedwell and rosebay willowherb, may be attractive in their own right. Only by taking prompt action whenever seedling weeds first appear, can a long term war on weeds be avoided.

Learn to distinguish between weed seedlings and cultivated seedlings. Sowing in orderly rows, especially in the kitchen garden, makes this task easier.

 

Manual weeding

The thought of hand-weeding is daunting to many people, but if you set to promptly and don’t let weeds take over the garden, this can be a relatively painless task. Indeed, old-fashioned hand-weeding is still the most effective and safe deterrent against perennial weeds.

Individual weeds can be pulled up directly by hand. This technique is best where a few large weeds have grown up between ornamental or crop plants, since, with care, the neighbouring plants are not disturbed. Wear gloves for protection, especially when dealing with stinging nettles or thistles. Pull them gently but firmly, holding the main stem as close to the soil as possible, to remove the whole root system intact. Many perennial weeds can regrow from severed root sections left in the soil.

For dealing with more widespread weeds, a hoe — either a draw hoe or a Dutch hoe — and a small border fork will be needed. A hand fork, trowel and onion hoe may also be useful. Use an onion hoe, a short-handled version of the draw hoe, where plants are growing close together — in seed beds and rock gardens, for example. Drawing the hoe towards you, cut off the weeds at soil level with a chopping action. Be careful not to damage the tops of young ornamental plants.

Use a Dutch hoe for general surface hoeing or between crop rows, working with a skimming action back and forth through the soil to sever weeds and remove their roots. A border fork should be used only to loosen deep-rooted weeds around the base of a plant — remove the weeds by hand to avoid disturbing the soil round the roots of ornamental plants.

Sometimes perennial weeds such as couch grass and ground elder become entangled with the roots of ornamental plants. The only manual solution is to dig up both, separate them by hand and replant the ornamentals.

Collect weeds to make sure they don’t re-root. They can be put on the compost heap unless they bear seed heads, in which case burn them.

Choosing weedkillers

Chemical weedkillers — herbicides — take much of the physical effort out of weeding, but they need careful handling and application. Some gardeners prefer not to use them for ecological reasons, but they can be very effective against difficult weeds. There are several types of weedkiller, classified by their mode of action.

Chemicals referred to below are the active ingredient, not the trade name — read the contents label on weedkillers carefully if you are unsure.

Selective foliage-applied types kill only certain plants, leaving others unharmed. These are commonly used on lawns — for example 2,4-D, which selects all broad-leaved weeds among narrow-leaved grasses. Here, the selective principle relies on most of the weedkiller running off the narrow, channelled grass leaves, but wetting the broader weed leaves. Similarly, alloxydim-sodium selectively kills most grass weeds growing among broad-leaved ornamentals.

Non-selective foliage-applied types kill most plants they touch. Some have a contact action, killing only the parts above ground which are directly touched by the chemical, for instance glufosinate ammonium and paraquat with diquat mixtures. Others are translocated — absorbed into the plant’s circulatory system — and kill the entire plant including roots and bulbs. These include glyphosate which takes several weeks to act thoroughly, but is very effective. Some non-selective types can be applied selectively by spraying or painting on to individual plants.

Soil-applied residual types, such as dichlobenil, remain active in the soil for some time and are taken up by the roots. They are effective against existing weeds and subsequent germinating weed seeds — they act in fact as weed preventers — so are useful for clearing land which won’t be used for several months.

Some soil-applied weedkillers have a selective action when used in low concentrations, or a nonselective action at higher doses, so follow manufacturer’s instructions carefully.

Total weedkillers, for example sodium chlorate (nowadays sold with a fire depressant), are used for clearing scrub-land. Since they can remain active in the soil for up to one year or more, do not use them among ornamentals or crops or on land soon to be used for crops, ornamentals or lawns.

 

Applying weedkillers

Weedkillers may be sold as liquids which need dilution, as dry granules for direct application, or as wettable powders or soluble granules. According to the type, they are applied by watering can, sprayer or sprinkled over the soil. Check the manufacturer’s instructions for application.

Where foliage-applied types are suitable for sprayer application, this is the most effective method, giving an even coating of fine droplets which do not run off the leaves. Choose a calm day when the spray won’t drift on to ornamental or food plants. Spray systematically to avoid over-dosing some and under-treating others.

You can make an effective spray drift guard for a pressurized sprayer. Cut the tube off an old plastic funnel so that the funnel will fit snugly over the tip of the spray nozzle. Secure it tightly with a Jubilee clip. When spraying weedkillers do not pump up the sprayer as much as you would for an insecticide or fungicide — you should be able to get very close to the weeds.

When applying liquid weedkillers to bare or open ground, use a watering can. The standard watering rose can be fitted, but for more even distribution replace it with a dribble bar. Walk across the area systematically and at a constant speed.

Granular types need careful application. First calculate the total area to be treated and weigh out the appropriate total quantity of the chemical. Then square off the bed into small segments and take enough chemical to treat one segment at a time.

Where individual weeds are growing too closely among garden plants for any kind of weedkiller treatment to be practical, a paint-on formulation of glyphosate can be used. In lawns, isolated weeds, such as scattered plaintains, can be treated individually with an aerosol-type of lawn weedkiller.

Whichever type of weedkiller you use, it is important to wear rubber gloves while mixing and applying it. If any chemical does get on to the skin or eyes, wash it off immediately and check the manufacturer’s recommendations regarding accidental contact.

Weed suppressors

Systematic and continuous hand weeding, or the use of preventative herbicides as recommended here, will keep your garden clear of most weeds. However, there are other, almost labour-saving solutions that can solve the problem even before it arises. Prevention is better than a cure and several measures can be taken to suppress weed growth.

Ground-cover plants are ideal for covering every inch of soil in shrub and mixed border. By their very nature, they deprive emerging weed seedlings of light and space and colonize rapidly to form tight clumps Some will spread to form flowering carpets, like the shade-loving London pride (Saxifraga x urbium), lungwort (Pulmonaria sp.), the red-flowered deadnettles (Lamium maculatum) and the almost-invasive evergreen, blue or white-flowered periwinkles ( Vinca sp.).

Better in sun, but equally good as defenders of the soil, are the evergreen, blue-flowered and bronze-leaved bugles (Ajuga rep-tans), the blue catmints (Nepeta x faassenii) with their grey-green foliage and a long flowering season, the semi-evergreen Viola labradorica and several ground-hugging roses.

Low-growing shrubs give excellent ground cover over large areas, notably the evergreen spindles such as Euonymus fortunei ‘Coloratus’, tinged rose-purple in winter and ‘Emerald ‘n Gold’, with green, gold and pink leaves. Prostrate junipers (Juniperus horizontalis), the evergreen Californian lilac (Ceanothus thyrsiflorus re-pens) and the hummocky rock rose (Helianthemum hybrids), in a range of bright colours, are other good choices. In smaller gardens, ericas spread their lush foliage beneath bell spikes, particularly valuable with the winter-flowering Erica carnea which, unlike other heathers, tolerates alkaline soil.

Ivies smother the ground closely in almost any situation, providing an all year-round, rich green cover as a fine backcloth for early spring bulbs underneath trees and shrubs.

Mulch covers

traditionally-the-soil-between-strawberries-is-covered-with-a-straw-mulch-to-protect-the-fruit Another effective preventative measure is to cover the bare soil with a mulch. You can use straw, polythene sheeting, tree spats of bituminous felt or synthetic whale-hide strawberry mats in the vegetable and fruit garden.

Among ornamental plants, organic mulches are visually more pleasing and are good soil conditioners. Well-rotted leaf-mould, compost and stable manure can be spread in a 5-7.5cm (2-3in) deep layer over the soil, though these materials often harbour weed seeds.

Wood bark chippings make a decorative and long-lasting mulch, that withstands winds and keeps rain splashes off plants. Composted forest bark is finer in texture and a preferred peat substitute for acid-loving plants.

Small pebbles, stone chippings and coarse gravel look natural round alpine plants in the rock garden and raised beds. They keep the collars of plants dry and rot-free in winter and keep down weeds. They also act as a good obstacle to slugs and snails.

21. July 2011 by admin
Categories: Weed Control | Tags: , , | Comments Off on Methods for Controlling Weeds

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