|Brown lacewing larva|
In perennial gardens we don't need to be this fastidious. Leaves, plant debris, and flower stems equal insulation and nesting sites, including nesting sites for cavity-nesting bees and solitary wasps. If you grow apple trees then yes, cleanliness is important so the leaf litter under the trees does not harbor pest populations or fungi such as apple scab.
|Green lacewing larva|
|Adult green lacewing feeding |
on pollen on Sprengel's sedge
Adult lacewings feed on pollen and nectar from a variety of plants including forbs and sedges; they also feed on the honeydew created by aphids.
|Close up of brown lacewing larva|
Lacewings are just one of many beneficial insects that need plant debris and leaves left in the garden. Cut down your perennial garden in late spring leaving 12-15" of perennial stem stubble (for cavity-nesting bees). Keep the debris instead of bagging it and use it as a natural mulch (combined with leaves) by laying it on the ground among the emerging perennial plants. The perennials will cover the debris in no time as their new leaves emerge and flower stalks form.