With global warming, drought threatens. Water deficit sets in during winter. Being satisfied with our rainwater reserves requires us to consider new cultivation techniques, more ecological, but also more labor-saving.
... or reconsider the "clean garden" question
"The garden must be clean": this is the leitmotiv that has been preached to gardeners for decades. Agronomists in favor of monoculture, a sort of pride in a vegetable garden with nothing sticking out, perhaps also more or less subliminally by the sellers of treatment products? The "golf course" or very formal garden is finally beginning to fall out of fashion, it is gradually giving way to the informal, to the naturalist garden that favors declining biodiversity, to permaculture...
This is just as well, because we have to adapt to global warming, which is drying and overheating our garden more and more. What can we do, if not try new cultivation techniques to save water? To finally take into account ecology, which considers all living beings in their environment and their complex relationships? For, most often, these inter-species relations are a relationship of mutual aid: for millions of years, these living beings have coexisted by adapting to each other and living in community. But where in nature do we see a piece of land drying out in the open air? Nowhere, because nature hates emptiness and is quick to fill it. Keeping the soil covered with vegetation is definitely a way to save water.
Why does land without ground cover deteriorate and dry out?
When soil is bare, freshly turned and worked, it is lumpy and easy to plant, and transplanted plants easily sink their roots into it. However, just after the first heavy rain, a so-called "capping" crust is created, especially on clay or loam soils. The heavy rain (or a copious watering) loosens the soil, the clay or silt is transformed into very fine particles suspended in the water, then settles on the surface in a hard surface layer. This layer bakes in the sun and becomes cemented.
Neither water nor air can penetrate this impermeable layer, which will greatly limit the development of the planted vegetable. Moreover, future rains, instead of gently infiltrating the soil, will either remain in puddles and evaporate very quickly, or run off if there is a slope, and carry soil with it. This rainwater supply is therefore lost to the plants.
Not only does the crust prevent water from infiltrating, but also, by a powerful capillary phenomenon, it sucks the water from the deep soil towards the surface where it evaporates, and amplifies the phenomenon of dehydration.
The dehydration of the soil does not only occur in summer, in winter, especially during periods of frost and wind, a huge quantity of water evaporates instead of infiltrating and going into the water table.
Even if there is no crust, on a bare and freshly hoeled soil surface, the sun evaporates the water much too quickly (imagine a sponge in the sun). On black soil, sunlight causes overheating, which is beneficial in early spring, but disadvantageous in summer.
Finally, overheating, like the crust of threshing, is unfavorable to the life of the soil, especially for the earthworms that produce the clay-humus complexes so necessary to plants.
Fill the garden with plants to water less
For a few years now, we have been trying to fight against this bare soil by mulching. Mulching is very interesting, but there is never enough plant debris in a garden to mulch everywhere.
Another solution is to imitate nature: no gaps!
- put an inter-culture (when the garden is empty) in winter or at the end of summer in the garden: a green manure or simply let local annuals grow, plant lamb's lettuce, forget-me-not...
- avoid cleaning up your garden too much, leave selected weeds (often annuals) between the vegetables for their tranquility (easy to pull out) and their attractiveness (for you as well as for insects): as long as they do not cover the vegetables, they do not bother them. A potato, for example, is not bothered by anything.
- stop trying to control your garden completely: each plant in its own place, perennials spaced regularly, no spontaneous sowing. Well, no! change your perspective, accept a form of wilderness, go from formal to informal style. Of course, it's also a matter of taste, but letting the flowerbeds thicken and become dense, filling the holes with annuals that take care of themselves until the perennials have grown enough volume are methods to avoid water evaporation. Moreover, it greatly limits the work of weeding: yes, we don't leave everything! It is a permanent balance to maintain, between the poppy that sometimes sows too much and the delicate perennial plant that is pampered, but it requires much less work than systematically weeding everything: once the plant cover is dense, very few new seedlings germinate and there are far fewer watering cans to carry.
Role of the ground cover plant
When the land is covered with plants, even small ones or even weeds, because it is better than nothing :
- the soil is protected from direct sunlight that dries out and overheats.
- the foliage absorbs the pressure of heavy rains: there is no crust of battance.
- the root network allows a natural drainage of the soil: the rain infiltrates quickly along the roots instead of evaporating.
- the foliage transpires during the day, but in return, the plant collects the morning dew (atmospheric water), part of which runs down the stems and into the soil.
- Under the layer of leaves, the atmosphere remains more humid and creates a microclimate conducive to life.
- weeds or other companion plants maintain the rhizosphere in good condition (symbiotic micro-organisms of the plants), which allows a better water balance of the soil and a certain help when replacing the weed by a cultivated plant.
- plant tissues are waterlogged, and are therefore generally a means of maintaining water in your garden
- the shade created on the foot of productive plants can be very useful in case of heat wave.
On the other hand, the fact that it is no longer a monoculture is very favorable to biodiversity, and therefore to the presence of small auxiliary fauna: for example, companion plants can flower in the low season and allow foraging insects to feed. Finally, some weeds are quite simply rare and tolerating them a little simply allows them to exist, such as the harmless Kickxia elatine.
Counteract the harmful effect of bare soil with weeds, the so-called weeds!
The gardener's work must evolve and be refined: rather than wanting to control everything 100%: water, plants, nutrient inputs, perhaps the gardener must trust nature more and imitate a system that has been developed over millennia and has proven itself, leave aside "clean", let go of complete control of the environment: accept a quota of weeds.
How to use weeds in the garden?
We will only allow those that are easy to remove, therefore most often annuals, and to do this well, we will allow those that we like, those that can be eaten, those that are melliferous, etc., to reseed themselves. This also means learning to recognize them.
Obviously, we will avoid leaving quackgrass, perennial nettles and bindweed in the middle of the beds, although bindweed can also be useful and often comes from an imbalance (see the article on field bindweed), or annuals that are too cumbersome.
The principle is to look at what sprouts spontaneously or to sow it yourself, and to let the selected seedlings develop after working the soil as long as there is nothing to cultivate in their place. When the time comes to plant or sow, just make the hole without enlarging it too much, then watch out for the balance between the two types of plants, avoid too much competition for light.
Some examples of weeds that can be tolerated and used in the garden :
- plantains, Plantago coronopus, Plantago lanceolata, Plantago major, perennials, but easy to pull out, they are relatively beautiful in flowers and melliferous.
- Robert's cranesbill, Geranium robertianum, a very cute and melliferous annual which appreciates semi-shaded or shaded spaces; it is happy in a bed of small fruits for example or in a vegetable garden surrounded by fruit trees. Its light foliage does not overpower its neighbors.
- Its counterpart in a sunnier and drier garden is the Pyrenean cranesbill, Geranium pyrenaicum, a melliferous plant whose small flowers are of a beautiful vibrant mauve.
- less aesthetic, but still native is Geranium dissectum, the cut-leaved geranium, the plant is interesting in basal rosette, but its flowers are tiny.
- the daisy and the veronicas, small and pretty... ex Veronica chamaedrys, which can be marvelous in a bed.
- the poppies, absolutely magnificent, but high
- the purple lamier, Lamium purpurea, not very annoying and sometimes blooming in winter so necessary for the foragers.
- the fumitory, Fumaria officinalis, with light foliage that protects the soil without shading it too much.
- wild pansy, Viola tricolor
- chickweed, Stellaria intermedia, small and harmless
- the red chickweed, Anagallis arvensis, cute, well covered and very low.
And certainly many others to experiment with...
Some cultivated plants play the role of weeds to perfection, such as forget-me-nots, red mustard, whose foliage is magnificent in winter, borage, lamb's lettuce if you let it reseed itself (and it's good too!)...
Keeping your soil always planted means maintaining a balance between what you leave and what you remove without wanting to make a clean sweep. The species to be used are certainly numerous and will depend in part on the cultivated area. As you leave this system of over-weeding, you might be amazed at how beautiful this overflowing, crowded garden is! For those who like neatness, these exuberant beds or vegetable gardens will find grace by drawing well-defined borders around them.
No doubt other old cultivation techniques to limit water loss have been lost with intensive agriculture and are to be rediscovered. Moreover, this vegetal cover of the soil can be combined with the technique of mulching and agroforestry (associating trees and herbaceous crops). But we can already change our mentalities in this period of strong extinction and act at our scale, because we must understand that these weeds are only local plants, hosts of a procession of associated species (microorganisms and animalcules of the soil, insects, earthworms...), which seek a space to live, whereas they are stupidly chased away from the edges of the fields, the edges of the road or our gardens, sometimes for very bad reasons.
Weed: the weed of crops is the plant that ends up in the middle of the field, the bed or the vegetable garden without being intentionally sown there. From the point of view of the "clean garden" or intensive agriculture, it is a nuisance and must be weeded. From the point of view of ecology, it is a pioneer plant, that is to say, it serves to re-vegetate a disturbed area.
Clay-humus complex: a healthy soil structure where clay (mineral) and humus (stable organic matter) are associated; they are made by earthworms and are very beneficial to plants in that they prevent leaching and therefore the escape of nutrients from the soil.
Ecology: science that studies living beings within their environment, the complex relationships they have with this environment and with the other species present. Different from political ecology, which deals with man's relationship with nature.
Monoculture: agrosystem where only one species is cultivated and tolerated. E.g. a field of wheat in agriculture, or on a smaller scale, rows of vegetables in a completely weeded vegetable garden. Weeds are banished.
Rhizosphere: all the micro-organisms living in the immediate proximity of the plant's roots. Extremely more numerous than elsewhere, they maintain symbiotic and cooperative relationships with the plant and create an extremely profitable synergy. See the article Rhizosphere, micro-organisms and plants, a winning team.
