Why a Garden Mulch is Better Than a Pre-Emergent Weed Killer For Preventing Winter Weeds

As the winter in Mediterranean climates is also the rainy season, weeds can germinate and cover wider areas so rampantly, that the gardener is usually interested in preventing weeds or at least keeping them down before they spread, develop, and really start to cause problems. In large-scale situations, the professional landscaper may resort to using pre-emergent herbicides, which kill the weeds shortly after they’ve sprouted. Some products are available for application in the private garden, and many home gardeners are attracted by the thought of their garden being weed-free for the duration of the winter.

There are a number of excellent reasons however, why the temptation should be resisted, especially considering that an alternative in the form of organic mulch, does exist, at least for the small scale of the private garden. Before dealing with the benefits of organic mulch, let’s look at the drawbacks of applying pre-emergent weed killers.

We should go forward with this short article. *Pre-emergent herbicides possess residual properties, meaning that their poisonous ingredients are active in the topsoil for a certain period of time. The correct dosages per square meter or yard have to be strictly adhered to, in order to avoid damage to neighboring plants, and to the health of the soil itself. This entails careful calibration of the sprayer, something that’s easier to do in large open spaces, but far more difficult in small spaces.

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*Most products are in any case, entirely unsuited to private gardens, as they can’t be applied near herbaceous plants. The few that are suitable are usually available in granular form as well as liquid solutions to be sprayed. It’s not easy from my experience to spread accurately the granules according to the weight per area ratio specified by the manufacturer.

*Even when applied completely properly, the herbicides will adversely affect the soil’s fauna and flora, killing or driving out a wide range of organisms that inhabit the soil and contribute to its ecological balance. This has far-reaching consequences for pest and disease control, and for the desired crumbly structure of the soil. In spite of this, pesticides in general, are a serious source of river and lake pollution.

The best alternative for weed prevention is to spread some form of organic mulch, such as decorative wood chippings, on the ground and between the plants. While a mulch layer is generally ineffective against perennial weeds, by preventing germination, it’s probably the best measure against annual weeds. Experience shows that the anti-germination properties of organic mulch are far superior to those of inorganic materials such as pebbles or stones. Having said that, as opposed to herbicides, it contributes massively to the positive state of the soil; the medium in which the plants grow. These can be summarized as follows.

*Organic mulch acts as an insulating layer for the topsoil, regulating the temperature at this crucial level. In the mild winters common to Mediterranean climates this may be less significant, but it’s tremendously important in reducing the topsoil temperature during the summer, where highs of 50c aren’t uncommon. Many physiological processes, such as water and mineral uptake, are severely retarded at these topsoil temperatures.

*Organic mulch slowly breaks down to add rich humus to the soil, thereby improving the soil’s crumbly structure (and thus its aeration), and expanding the volume and range of the soil’s fauna and flora. In this regard, it also provides raw material for essential soil organisms, such as earthworms, and so can be seen not only as a weed prevention measure, but in direct distinction to pre-emergent weed killers, as a soil and environment enhancing measure as well.