Zucchini suppresses some weeds.
image by Christa Richert: sxc.hu
Weeds rob nutrients and sunlight from vegetable seedlings, effectively choking them out of the bed. Drawn to the moisture and rich soil of your vegetable beds, they quickly take over if left unchecked. Eradicating weeds is nearly impossible---there will always be more next year. Controlling the bulk of the problem, at least until the vegetable plants are large enough to no longer be bothered by a few interlopers, is much easier but still requires patience and constant vigilance.
Turn over the top 5 to 6 inches of soil before planting. Remove any weed stems or roots from the soil and destroy.
Plant in rows so weeds are easy to spot amongst seedlings. Hoe between the row daily to disturb the soil so weeds can't take root. Pull out weeds between the rows as they are noticed and any weeds that grow near seedlings.
Lay black plastic or weed cloth over the bed. Cut holes where you plant the seedlings. Be aware that plastic prevents natural moisture from penetrating the soil.
Apply an organic mulch around garden plants alone or on top of weed cloth. This preserves soil moisture while preventing weed seeds from getting the sunlight they need to germinate.
Remove large weeds or weeds with long tap roots with a weed cultivator. Stick the pole section of the cultivator down in the soil right next to and parallel with the weed root. Angle slightly to grasp the root between the claw on the bottom of the pole and pull up.
Apply a herbicide for large infestations. Herbicides are toxic so use a type specifically formulated for vegetable gardens and avoid eating produce until after washing.
Plant crops that suppress weeds. Low-growing vegetables rob weeds of the sunlight they need to survive. Squash, melons and beans are acceptable suppressors.