Gardeners know the importance of mulching around plants to suppress weeds and conserve soil moisture, but are there instances when mulching is not a good idea? The answer is yes, in particular when creating a pollinator-friendly landscape.
To understand the importance of bare ground, you must first be aware of just how many pollinators it affects. According to research at the University of Vermont, there are 4000 species of native bees on the North American continent and of these, 70% nest in burrows in the ground. (The remaining 30% build their nests in the hollow stems of plants.) 1.
As explained by Dr. Jonathan Larson, Nebraska Extension Entomologist, the soil plays an integral role in supporting the reproduction of native bees. The female digs in the soil to excavate a tunnel and brood cells. She then collects wads of pollen, called bread, packs the bread into the brood cells with her eggs and finishes by sealing the end of the tunnel. The newly-hatched young are then supplied with food to grow and develop. 2.
Like all things real estate, it’s location, location, location for ground-nesting bees and wasps. To maximize nesting opportunities, the Xerces Society recommends sites ranging from flat to the vertical to benefit different species’ slope preference. 3. Sites should be located in a sunny area with well-drained soil. Regardless if you have a few square inches or several square feet to devote to bare ground, there will be ground-nesting insects that call the place home.
Besides being important to ground-nesters, bare ground is also beneficial to butterflies for puddling purposes. As moisture evaporates from the ground, minerals are brought to the soil surface. These minerals are necessary to butterfly health and it isn’t unusual to see lots of butterflies sponging around the edges of drying mud puddles, taking advantage of the available minerals.
Shallow areas that stay fairly moist are good places to support butterfly puddling. If you don’t have an area like this in your landscape, you can create one by excavating a spot, no deeper than 1 inch, sloping the sides to allow the butterflies a place to rest. Water the area during dry spells to ensure there are minerals available to butterflies as the water evaporates.
To fully support pollinating insects we have to think holistically. While attracting pollinators with plant food sources is necessary, providing nesting and egg-laying sites are essential as well. Bare ground is one of the most important ways to support life processes and health for pollinating insects.
- Dr. Jonathan Larson, Entomologist, Nebraska Extension in Douglas-Sarpy Counties