Living Mulch

Competition: the weak point

A living mulch shares the soil with the crop it protects. Research on living mulches names competition for water and nutrients as its main risk, especially while trees and crops are young and their root systems are small. A cover that grows too tall or too vigorously can take more than it gives.

Three things reduce this risk. The choice of species: low, creeping plants compete less than tall grasses. A free zone around young trees, often covered with dead mulch instead, so that the tree's roots have the first claim to water. And management: when water becomes scarce, the cover is mown, and the cut material stays on the ground.

Living mulch in a Mediterranean climate

In a Mediterranean climate living mulch follows its own rhythm. A perennial cover such as white clover, common under fruit trees in temperate regions, needs water in summer. Without irrigation it fails, and with irrigation it competes with the trees for every litre.

The plants that work are the ones that have adapted to the rhythm of the climate. Subterranean clover is the classic example. It grows in winter and spring, flowers, pushes its seed heads into the soil, and dies back in early summer. What remains is a layer of dry straw that protects the ground through the dry months. After the first autumn rains the seeds in the soil germinate, and the cover closes again. Annual medics, such as bur medic, follow a similar cycle.

This means that in the Mediterranean the living mulch and the dead mulch are the same cover in two states. In winter it is alive and grows; in summer it is dry and protects. The same area looks green in March and straw-coloured in August, and in both states the soil stays covered.

How Terra Humana understands living mulch

For Terra Humana living mulch is the logical extension of the principle that bare soil is a wound. Where possible, the soil should be covered by something that grows on the site and renews itself, rather than by material that must be brought in and replaced. A self-seeding winter cover is exactly that: once established, it returns every year without being sown again.

We do not see it as an alternative to dead mulch, but as its partner. Around young trees, where competition matters, dead mulch or a small patch of sheet mulching keeps the soil cool and leaves the water to the tree. Further out, the living cover takes over. Over the years, as trees cast more shade, the balance shifts again, and the ground layer changes with it. The aim is soil that is never left bare, in any season and at any stage of the planting.