Caring for garden soil in a wild bee-friendly way: Preserving nesting sites

Key points at a glance

• About 75 per cent of all native wild bee species use the ground as a nesting site; digging destroys these brood structures irreparably.
• Soil that is permanently covered with vegetation or slightly compacted offers the safest protection for larval development.
• Avoiding mechanical soil cultivation protects soil ecology and promotes pollination performance.

Soil ecology as a foundation for life

In July, many ground-nesting wild bees reach their peak activity. Species such as the red mason bee (Osmia cornuta) or various mining bees (Andrena species) have already established their nests, while specialised species like the grey-backed mining bee (Colletes cunicularius) are actively stocking their brood cells. The soil is a highly sensitive space during this phase. If we manage our garden soil in a wild bee-friendly way, it primarily means protecting the so-called brood chambers beneath the surface.

Traditional digging, often seen as preparation for the next planting season, acts as a disaster for these insects. The nesting tunnels are destroyed, the larvae are brought to the surface, where they are exposed to predators or unfavourable climatic conditions. Instead, you should opt for nature-friendly soil care that preserves natural structures.

Comparison: Soil cultivation vs. wild bee protection

Practical tips for maintaining nesting areas

1. Maintain soil undisturbed: Avoid any digging work in areas with little vegetation, especially in sunny, sandy or loamy spots. These are essential for species like the hairy-footed flower bee (Anthophora plumipes).
2. Allow selective compaction: Light footpaths or unplanted, open patches of soil are often more attractive to wild bees than heavily fertilised, loose garden soil. Leave these areas untouched.
3. Rely on organic fertilisers: Avoid synthetic fertilisers. Compost should only be applied superficially as a mulch so as not to disturb the soil structure by working it in.
4. Create a variety of surfaces: Ensure an alternation between densely vegetated areas and deliberately kept free, vegetation-free patches of soil, which serve as starting points for nest building.

Care without digging also promotes soil fauna, such as earthworms (Lumbricidae), which naturally aerate the soil. Healthy soil is the foundation for pollination in your garden. If you discover small mounds of earth or tiny holes in the ground in July, this is a sign of a functioning, wild bee-friendly ecosystem. Leave these structures until well into the autumn, as the development of the next generation often takes several months.

Frequently Asked Questions

Why is digging harmful to wild bees?

Digging destroys the underground nesting tunnels and brood chambers where the wild bee larvae develop, leading to the death of the population.

How do I recognise nesting sites in the ground?

Look for small holes in the ground, often surrounded by fine mounds of earth (craters) in sunny, vegetation-poor areas.

How do I fertilise without cultivating the soil?

Spread mature compost only as a thin layer across the surface. Soil life will work the fertiliser into the ground over time itself.

Main article: Ground-nesting wild bees in the garden: Protecting their habitat