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

Key facts at a glance

• Small holes in the ground are often valuable nesting sites for specialised wild bees, not a sign of a pest infestation.
• Over 70 per cent of native wild bee species nest in the ground, not in insect hotels.
• Open patches of bare soil are essential for the survival of these species; therefore, avoid mulch layers and intensive soil cultivation.
• Observing their flight behaviour can help you determine whether they are wild bees or solitary digger wasps.

Why soil is more than just dirt

If you discover small, circular holes in your garden soil in July, it is an indicator of the high ecological quality of your land. Many wild bee species, such as members of the Andrena genus (mining bees), depend on bare, unvegetated soil patches. While insect hotels are important for wood-nesting species, they only cover a fraction of the nesting opportunities required. Ground-nesting species dig branching tunnel systems, where they create their brood cells and provision them with pollen and nectar.

Intact soil providing nesting sites is a critical limiting factor for local biodiversity. Even with an abundant supply of native flowering plants, populations can collapse if there is no access to open, sun-exposed earth. These areas are not only nurseries, but also serve as vital sunning spots for the insects to warm up in the morning due to their thermal properties.

Analysis: Identifying the inhabitants of earth nests

Not every hole in the ground is inhabited by a wild bee. Solitary digger wasps (Spheciformes) also use these structures to rear their young. You can distinguish between them by closely observing their behaviour:

How to protect nesting sites in your garden

To ensure the next generation can grow up successfully, you should implement the following measures in areas where nesting tunnels have been discovered:

1. Keep it open: Completely avoid applying mulch in this area. Bark mulch or wood chippings prevent the insects from accessing the soil.
2. Undisturbed soil: Do not dig or till the soil in areas where they have settled. The nesting tunnels often run deeper than you might think and can be destroyed by mechanical disturbance.
3. No chemicals: The use of pesticides or synthetic fertilisers is counterproductive. These substances directly harm the sensitive larval stages.
4. Area management: Design your garden to include sparse vegetation and vegetation-free, sunny spots (such as embankments or gaps between paving). These places provide the necessary infrastructure for ground-nesting wild bees.

Frequently asked questions

Are ground holes harmful to my lawn?

No. The holes are usually very small and indicate a healthy wild bee population. They do not damage the turf.

How can I tell if it is a wild bee or a wasp?

Wild bees carry pollen on their bodies, whereas digger wasps actively carry prey such as spiders or caterpillars into their nests.

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• Wild bee forage plants: Optimal nutrition in sandy soils
• Mining bees in the garden: Habits and protection of the genus Andrena
• Managing garden soil for wild bees: Preserving nesting sites
• Wild bee ground nesting aids: Sand patches for ground-nesting species
• Avoiding soil compaction: Securing habitats for wild bees