Weed control in preparation for sowing

Weed control

Weeds can be controlled by mechanical removal or exhaustion. Removal by hoeing, digging out or repeat cultivation is an effective control for most annual and biennial weeds but less effective (as most gardeners know) for perennial weeds with underground rootstocks. It is possible to exhaust persistent perennial weeds by repeated removal, but it is easy to allow a weed to recover if repeat cultivation is delayed for any reason (e.g. unsuitable weather). Other strategies like fallowing, or covering the ground with plastic mulch are usually essential to success.

Fallowing The aim of fallowing is to leave land exposed to provide an opportunity to deal with weed problems. During the fallow period a number of strategies can be followed to clean the land depending on the soil type and weed burden. Deep ploughing will reduce perennial weeds by causing a proportion to rot, and by producing a temporary check to their vigour as they are forced to re-grow to the surface. This burying must be followed by summer fallowing to be fully effective as a weed control measure. The aim of summer fallowing is to expose and dry out the rootstock and rhizomes of established perennial weeds, and to exhaust their growth reserves. On lighter soils the roots can be dragged out with a harrow or rake as the soil dries. On heavy soils the land should be very roughly cultivated or ploughed in spring to leave the maximum surface area and depth exposed. The resulting large clods and ridges should be left to dry out completely in the spring and early summer to 'bake out' the perennials.

The Stale Seedbed technique

The "stale seedbed technique" can work well to reduce competition from annual weeds whose seeds will remain in the soil after clearance. This method involves preparing a seedbed then delaying sowing to allow a flush of weed seed germination from the surface layers. This flush of weeds is then killed, by surface cultivation/ hoeing, before sowing your seed mixture onto the cleaned "stale" seedbed - the surface of which now has a reduced weed seed burden. Timing and weather conditions are important for success. The soil must be moist and warm enough to encourage weed emergence. The weeds must not be given enough time to set new seed or develop new persistent root stocks. Cultivation should be shallow to avoid bringing fresh buried weed seeds to the surface.