Gardening Advice

Weed removal, alternatives to chemicals

“Weed” is a subjective term, and all plants have their place in nature. However, our gardening culture requires us to remove unwanted plants from our terraces, paths and kitchen garden.

How can we replace weed-killers, which are so effective and so widely advertised?

You could almost forget that they are toxic and not at all biodegradable. But scientists have the proof: weed-killer molecules accumulate in the soil and find their way into groundwater. The lobbyists may have more power than the researchers, but some countries are starting to ban the use of these products.

France will undoubtedly follow suit in a few years. At Villandry, we stopped using glyphosate and anti-germination treatments in 2010. We have established several different practices to combat grasses on the paths of our garden, a listed historical monument.

The flowerbeds have always been weeded by hand.

On the main paths, the steady stream of thousands of visitors prevents the grass from growing (like Attila on his horse!). The other paths, less used or more subject to damp, are quickly colonised by annual bluegrass, plantain and groundsel.

The squares of the kitchen garden, which can be admired from the château’s tower, are punctuated by narrow gravel paths. Watering the vegetables and flowers results in many adventive species growing between the box hedges. To avoid these weeds, we removed the gravel, dug up the soil to a depth of 5 cm and laid a double-thickness layer of Bidim geotextile (a kind of permeable carpet). Finally, we covered the geotextile with a 5 cm layer of gravel to restore the original appearance of the garden. After one season, we can confirm that the system is effective, and that even if a few weeds take root in the textile, they are easy to remove. However, it remains to be seen how long the geotextile will last.

Around the pond, where there are lots of paths subject to constant dampness, we use a thermal weeder. This machine consists of two burners heating to 1200°C supplied by two 13kg bottles of propane gas. As it passes over the plants, the heat causes a thermal shock which destroys the cells and prevents photosynthesis in the plant. However, this method does not destroy the roots, so the operation has to be repeated frequently, especially when spring is wet.

Another solution is to change the ground type. For example, we will be replacing compacted limestone paths with sand paths so that they are easier to treat mechanically. There are tools available for harnessing to a tractor which can treat loose ground (sand and gravel) by cutting or uprooting plantlets while levelling the ground using a mesh and a roller. This method eliminates the use of gas, but we will still need oil to power the tractor…

For small areas, we have no proof of the effectiveness of potato cooking water. But you can use white vinegar: pour 5 litres of vinegar and 5 litres of water into a sprayer and spray the weeds on a sunny day. The action of the acetic acid and the sun burns the weeds. This is a very economical solution, and the vinegar degrades quickly in the soil.

So far there are no 100% ecological methods of combating weeds. I recommend thinking carefully about the type of soil you need to maintain in order to find the best solution for avoiding laborious weeding. Sometimes, just a few adjustments are enough: replacing the mortar in a terrace, for example, or, even more aesthetically, sowing small flowers such as fleabane or campanula in the joins as a lasting visual treat.

Laurent Portuguez
head gardener 

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