We can never win the battle with weeds, but we can reduce their impact to very low levels.

How we manage weeds depends on how dry the climate we live in is, how big our vegetable garden or orchard is, how much time we have, what tools are available to us, and what leeway we have to do what needs to be done when it most needs doing.

Managing a vegetable garden is different from managing a yard full of fruit trees which is different from managing a lifestyle orchard. So we will consider these separately.

This page is written to help home food gardeners, and practices are quite different to those relevant to commercial garden and orchards.

It is also written with the assumption that most of us would prefer to use the chemicals known to be very safe, from a human health point of view.

The most important thing to bear in mind is that there is no one thing that will 'do it' for every unique garden situation. Usually, a combination of strategies works best.

General Principles

• 'One years seeding means seven years weeding'. This pithy little saying is unfortunately largely true. Even one plant of some of the worst weeds will produce thousands of seeds to multiply the weed load in the following year. If is feasible, get to the weeds BEFORE they mature seeds.
• Disturbing the soil is as good as sowing weed seeds. Weed seeds can remain dormant in the soil for decades. When the soil is dug over, the exposure to light stimulates germination. Either avoid unnecessary digging, or be prepared to deal with the resultant swathe of seedlings.
• 'Prevention is better than cure'. Another irritating truism. But how true! One home grown plant from friends or family can bring with it bulbils of intractable weeds like oxalis or pieces of persisistant rhizomes such as couch grass. Check the soil-and mulch materials-you bring onto your property for persistent weed bulbs or roots.
• Striking at the right time can save time later. For example, spraying newly emerged seedling weeds will wipe out swathes of potentially large plants that are more difficult to spray later, and that take more time and more material to spray later. Hoeing on a hot day is very successful; hoeing in showery weather is less successful because some weeds will re-root in the moist conditions and will have to be later attacked again .

Managing weeds in the veggie garden
 

• Digging

• Spraying

Preparing an existing veggie garden for spring planting
For those of use who are primarily summer gardeners, glyphosate is a very good option for 'cleaning up' the existing veggie patch in preparation for the new season. This is especially important where there are weeds such couch grass and kikuyu grass which spread by underground rhizomes.
The most effective method in warm temperate and warmer areas is to spray out once in winter, and again when the first flush of spring weeds emerge, just prior to the big spring plant-up. This prevents winter seeding weeds making their deposit!

Spraying between rows of vegetables
Possible, but not for the faint hearted! Glyphosate is dangerous to all plants, and it doesn't distinguish between friend and foe. Lapse of concentration, sudden gusts of wind, 'bounce' and carelessness can cause you to damage or kill the produce of which you are so justifiably proud. This is high risk territory - almost irresistible to males, in other words! In our opinion, glyphosate is too risky to use as a between row weeder in a home garden of mixed veggies. There are, as always, exceptions. For crops which have waxy, water repellent coatings on the leaves, such as cabbages, broccoli, other brassicas and crambe, you can often get away with spraying between the rows WITH a spray guard, USING a lower rate, and WITH GREAT CARE.

Risks
First, on available evidence, there is no risk to human health, immediate or carcinogenic, from using glyphosate in the ordinary manner. And probably not even when used at much higher dosage. It works on a plant specific enzyme system, and seems to be well proven as safe for animals when used on weeds.
The real risk is what is euphemistically called 'collateral damage'. That is, plants you love and hold dear get a drift of glyphosate and are severely damaged or die. This can be caused by 'the bounce',  'drift', 'the drip' or carelessness.

• droplets can 'bounce' off hard packed soil and onto adjacent precious plants.
• a fine mist can be carried by breezes onto precious plants nearby
• it is not uncommon for sprayers to leak at the hose or the nozzle. Each drip is potentially lethal to the plant it drips on
• Males, especially, (spraying is 'mans work'!), like to push the envelope. It is always tempting to spray as close as possible to precious plants to minimize later 'around precious plant weeding'. Carelessness or a lapse in concentration can have serious consequences!

• don't edge your veggie patch with lavender or the like. Use non-living edging. (if you must edge with lavender, AND insist on using glyphosate, use 'English' lavender, Lavendula vera, as it has a quasi dormant period in winter and is less likely to be damaged vs winter active species such as L.stoechas)
• use a 'spray guard' on the end of your sprayer to minimize 'bounce' and 'drift'. AND be careful to keep the spray guard close to the soil as you spray.
• Use a nozzle that produces large droplets that are less likely to drift.
• NEVER spray when there is a wind. Fine (virtually invisible to the naked eyes, by the way) particles drift on even a breeze (use the right nozzle as above), but bigger droplets, too, will drift in wind. Pick a calm day. Early morning can be calm - especially in areas subject to coastal breezes.
• Check your sprayer for leaks - and fix them!
• Use low pressure to keep droplet size large and less likely to drift. The higher the pressure, the more the drift.
• Don't take risks! Remind yourself of the anguish and unhappiness that will result from an impulse to edge that 'little bit closer'.
• Use a dedicated sprayer for glyphosate. As long as you clean the sprayer THOROUGHLY, you can use it for insecticides (if you are that way inclined), fungicides (ditto) AND glyphosate - but it is high risk. In the real world, we get distracted, we mean to 'do it later' and all the rest. Play safe - have a dedicated sprayer for herbicides.
• Consider lowering the rate when spraying close to precious plants is unavoidable. A proven trick is to halve the rate, but add a couple of dessert spoons (the amount is non-critical) of urea to each 14 litre/gallon and a half approx knapsack sprayload (say a teaspoon to the gallon/4 and a half litres). This ultimately is almost as effective as the full rate, but takes longer to see a result. However, and this is the important point, it is less likely to cause damage from drift.

• Perennial weeds are killed, roots and all. Hoeing is ineffective on some weeds that can re-generate from the roots. Glyphosate takes care of this problem.
• Digging can be confined to the exact row where you want to put in your transplants. For example, once the garden is sprayed out, you could dig a row of the length you need (incorporating fertiliser and soil amendments such as peat, compost or sand), but only one spades width wide. The area between rows can remain undug. Slow release palletized fertilizer can be spread on the undug soil surface over the expected root run of your transplants. This saves physical effort.
• But more importantly, it means that the organic matter content of the undug portion of the soil is conserved. Digging oxidizes organic matter. Organic matter can still be incorporated into the soil by using mulches on the undug portion. The worms do the mixing.
• Minimizing digging means that fewer weed seeds are triggered into growth, meaning less work

• Hoeing

The best time to hoe is when the latest crop of weeds are at the small seedling stage, and the day is sunny and/or windy. Conversely, the worst time is when the soil is moist, the weather rainy, and the weeds well advanced.

The twin dangers of hoeing are-

1. risk taking-hoeing too close to the plants in the row and felling the work of weeks in the blink of an eye!
2. careless or inattentive hoe sharpening and slicing your finger open

• Mulching

Types of mulch

• Black plastic-generally unattractive, you can't fertilize during the growing season, a fiddle to put in, only useful for one season for various reasons. Total weed suppression, helps warm the soil, conserves moisture initially.
• Woven weed mat-difficult but not impossible to fertilize during the growing season, relatively expensive, requires lots of wire pins to prevent lifting. Total weed suppression, permeable to water, warms the soil, conserves water, will last around five years, maybe more if it has a mulch on top to protect it from the sun.
• Sawdust-very good if applied thickly, but it tends to crust, is difficult to get water thru. As it ages, weeds will germinate in it. It doesn't 'rob' the soil of nitrogen if left on the surface, but certainly does if dug in. Clean, easy to handle. It MUST be untreated sawdust, not treated!
• Hay- don't use it. It is usually full of grass and weed seeds.
• Straw-this is what is left of the wheat or pea plant or whatever after the seed has been knocked off. It is essentially weed free, has good weed suppressant qualities if applied to about 100mm/4 inches thick, conserves water, builds organic matter. It is also hard to find and bulky.
• Newspapers-very good if used at least 4 pages or so thick, when they will last about a year before the worms and weather have destroyed them. Wet them as you place them, or you will end up chasing them all over the yard. They will need additional material such as lots of grass clippings, or sawdust or bark on top, or they will simply blow away when they dry.
• Post peelings-last about two years, are good for putting over newspaper, but are bulky. Sometimes they contain weed seeds from the forestry ground where the posts were peeled and the peelings stored for cartage.
• Bark-the best topping for newspaper, woven weed mat, or even put over sprayed out ground. It is expensive, but it will last four or five years.
• Freshly pulled out weeds-these are fine as long as they are not seeding and as long as they are well wilted. However, they break down very quickly, and those on the bottom may re-root.
• chipped plant material - excellent, as long as there are no seeds in it.

Non Chemical Weed Control in Home Gardens- J Mississippi State University publication 1580, a brief fact sheet discussing general principals.
http://www.ext.msstate.edu/pubs/is1580.htm