Autumn has arrived in the northern Hemisphere, and with winter approaching, there are two weed issues that should be faced. One is how to prepare the garden so that the weeds are controlled to manageable proportions, and the other is how to deal with noxious perennial weeds right now.

The main problem with winter weeds in a Mediterranean type climate is the high rate of germination and therefore the capacity of the weeds to smother whole areas. This, can actually be advantageous in large scale situations, but not so in small garden beds. Of course the weeds can always be picked out periodically during the winter, but prevention is usually better than cure as the saying goes. The question is how and by which method?

The best way is to spread a natural, organic mulch over the bare soil to a depth of about 10 cm. Aesthetically speaking, the most appropriate material are wood chippings, although functionally at least, straw and even weeds can be used. Organic mulches are to be preferred to inorganic ones like pebbles or small rocks, because they not only inhibit germination more effectively, but they also improve the soil and general conditions in which the plants grow. Mulches are ineffective though in preventing perennials such as invasive lawn grasses. These have to be treated after they have emerged.

Another method of retarding winter weeds is one often suggested, but which is in my view highly undesirable in a small garden – namely the use of pre-emergent herbicides. These are weed killers that kill the weed seedlings shortly after germination. The crucial point to remember is that these are residual herbicides, effectively poisoning the top layer of the soil for a period of time ranging from two to six months.

Furthermore, their application requires considerable knowledge and experience by the user, in order to be both effective on the one hand, but without causing damage to the soil and to neighbouring plants on the other. The granular types are more suitable for a small area than the spraying of a liquid one. Needless to say, only qualified persons should carry out the work.

In big gardens, where there may be large spaces that have yet to be planted, the spraying of empty areas with a pre emergent, may be reluctantly considered, because mulching is often impractical over large areas, mainly for economic reasons, as would be removing weeds by hand through the winter.

There is though another way of managing weeds in these situations, which has none of the draw backs associated with residual herbicides, and that is to periodically mow the weeds, say once a month, by either a mechanical weed tool like a strimmer or if possible, even by a lawn mower. The weeds are not eliminated but kept under control. From all points of view this is better for the health of the soil, thereby creating better growing conditions when the open area is finally planted up.

Yet there is still important work to be done with the highly problematical perennial weeds at this time of year. These, in order to be eliminated, have to be treated with a systemic herbicide such as Roundup or other brands of Glyphosate. It should be remembered that Glyphosate, in order to get down to the roots, works slowly and when the temperatures are over 23-24 c. So at the time of writing, the beginning of October, this is about the last chance to effectively deal with the noxious perennial weeds until next spring.