Wild bee houses: tips for the garden
How can you help wild bees nest in your garden? What features must a species-appropriate insect hotel meet? We reveal how you can help the little hummers with nesting aids in the garden.
Wild bees perform a significant task in the garden because they are among the most important pollinators of all. Wild bees often fly earlier in the year than honey bees. As “belly collectors,” they also often pollinate flowers more effectively, which results in a higher harvest. At the same time, many wild bee species are highly specialised: Thanks to their special adaptation, they can pollinate native plants where other beneficial insects have no chance. Unfortunately, the number of wild bees is dwindling more and more: unsuitable habitats and a lack of diversity in the garden make life difficult for these small animals. If you want to support wild bees, you can do them a big favour not only with a flower meadow but also with a species-appropriate insect hotel. Here, we reveal what to consider when building wild bee houses and what mistakes to avoid.
Wild bee houses in the garden
If you want to support insects in the garden, you can achieve a lot with a nesting aid for wild bees. However, some points should be considered to ensure that the nesting aid is well accepted. Different species of wild bees prefer different hiding places: Hole bees and scissor bees, for example, feel right at home in hollow plant stems, while mason bees prefer hollow chambers in stone or wood. Therefore, to appeal to as many wild bee species as possible, it is advisable to use several different wild bee nesting boxes or even an insect hotel with different materials.
However, when buying such an insect hotel, you should keep your eyes open: Not all models offered are really suitable for wild bees. Especially a bee nesting aid with glass tubes for observation should be avoided – the water-impermeable material can lead to fungus of the brood and is thus more harmful than useful. Also the frequently used perforated and hollow bricks are conceivably unsuitable and are therefore just as little colonised by wild bees as the “willow rod clay walls”, the material of which is almost always too hard. Additionally, make sure there are no sharp edges inside the wild bee nesting box, as these can injure the delicate wings of the bees. The best option is therefore to build a wild bee nesting box yourself: Not only can you be sure that the materials used are suitable but it is also fun and easy to create with children.
Build a wild bee house yourself
Wild bee houses come in all shapes and sizes. In fact, the outer shape is of secondary importance at first because bees love around nest boxes just as much as triangular ones. Size is not critical either: several small nesting boxes can be just as helpful to wild bees as one large insect hotel. Instead, emphasis should be placed above all on the furnishings – these are decisive for whether the nesting aid is not only well accepted but also really helpful for these small insects. In fact, different species of wild bees need different nesting aids – bumblebees can be best supported even by a special bumblebee nest box. We have summarised the different nesting aids for wild bees for you here.
Wooden nesting boxes for wild bees
The best-known are probably nesting aids made of wood with pre-drilled holes, which are readily used by various species of wild bees. To prevent the wood from cracking during drilling or later during drying, drill into well-seasoned lengthwise wood, i.e. in the same direction as the grain. Holes with a diameter of three to six millimetres and the depth of a full drill length can then be drilled into this. Fresh wood blocks or holes drilled along the grain, i.e. into the end grain – this also includes tree slices – are not suitable as nesting aids, on the other hand, as they often crack and then become too damp. Also coniferous wood is unsuitable for bees because it tends to splinter – so it is best to use robust hardwood such as oak. Deadwood piles are a natural alternative to pre-drilled insect hotels: Rotten branches and dead trees are ideal nesting sites for wood bees and should therefore ideally be left loosely stacked in the garden. Here, too, only hardwood is suitable.
Wild bee houses from clay or loam
Perforated or hollow bricks are also often used in insect hotels. However, these have too large cavities, so they are rarely occupied by bees. Extruded interlocking tiles are much more suitable here: mason bees and leafcutter bees like to use the small hollow chambers of this type of tile as nesting aids. Alternatively, you can also make your own so-called bee stones by making small holes in clay and then firing them. However, the cavities in drystone walls and rock piles are also readily accepted by wild bees. So if you have some old natural stones in your garden, you can also provide a natural nesting aid with such piles of stones. Mud walls are also popular with wild bees but care must be taken that the substrate is not too firm, as furry bees and other steep-walled inhabitants dig their own tunnels. Unfired clay bricks have proved successful here – but these should not be placed directly on the ground, as they could otherwise draw water.
Nesting aids for wild bees from plant stems
Another commonly used form of wild bee nesting aid is bundling plant stems. Here, however, there is often confusion between pithy and hollow stems: While hollow plant stems (for example, bamboo or reed stems) are bundled horizontally and provide good shelter for solitary wild bee species, pith-containing plant stems are only accepted if they are placed vertically. They particularly like to colonise the stems of blackberries but mullein and dog rose are also accepted by masked bees and similar insects. But the stems do not always have to be cut off: If you leave pithy stems in the perennial bed and do not rigorously cut back the plants, wild bees will also find an excellent nesting site here.
Sand pits as wild bee houses
Many wild bees nest not only in dead wood or stone niches but often in the soil as well. Especially narrow bees but also silky bees and sand bees often dig their own tunnels in the soil, which they use for nesting. But unfortunately, only a few gardens still have uncultivated patches of suitable soil where the animals can nest. A sand pit can provide a remedy: Filled with drifting sand or loamy sand, it provides a good foundation for nesting. To ensure that the bees also feel comfortable, the sand pit should be filled with at least 25 cm of sand and be protected from rain and wind (for example, under a canopy). If adequate weather protection cannot be provided, a generous water drain should be installed to prevent excess water from accumulating.
Setting up an insect hotel for wild bees
In addition to suitable breeding sites, special attention should be paid to protection from wind and weather, as well as predators. Thus, the roof of the insect hotel should have a small overhang, so that the nesting aid is not directly exposed to rain. However, the use of protective glaze or paint is not recommended (especially for nesting material). As protection against predators, which like to plunder the nesting aids for wild bees, it may be worthwhile to stretch a wire mesh or net at a distance of about 20 cm around the wild bee house. In this case, the mesh size should be about 3 cm x 3 cm. Narrow-meshed bird nets from the garden, on the other hand, are not suitable because they are an obstacle for the insects and can become a death trap for inattentive birds.
In addition, there is the question of the right location. The nesting aid should face south and be protected from rain and wind, as a dry and warm nesting site is a basic requirement for successful breeding. Stable mounting is important – nesting aids dangling in the wind are not accepted by wild bees. Also, the insect hotel for wild bees should not be too close to the ground because here there may be shading from plants. Wild bees prefer sunny breeding sites with a clear approach path, so a site close to the ground is often unsuitable. On the other hand, bee-friendly plants near the nesting site are readily accepted. Seed mixtures are particularly well accepted in this regard, as their diversity allows them to provide for a wide variety of wild bee species over the long term. A watering hole nearby also makes the insect hotel much more attractive to wild bees.
To find out how beneficial insects fulfil their role as pollinators, read our article on bee pollination.