Don't clean up your garden just yet! Insects need some old brush to thrive in spring
Wait until daytime temperatures are consistently at least 10 C.
It's easy to get excited about spring and the gardening season ahead, but please avoid taking out the rake and yard waste bags just yet, or at all! A live-and-let-live approach to yard cleanup in both the spring and fall is actually much more beneficial for pollinators and other insects.
Not your average pile of leaves
Many moths and butterflies (known collectively as 'Lepidoptera' in the science world) spend the winter in leaf litter in their egg, larval or pupal form. For example, butterflies like the tiger swallowtail (Papilio glaucus) form expertly camouflaged chrysalises (pupae) on stems or litter — camouflaging them to look like dried leaves. In late spring, the butterflies break free from their chrysalises to pollinate and drink nectar from flowers such as bee balms, milkweeds and coneflowers.
The caterpillars (larvae) of luna moths (Actias luna) also spend winter in leaf litter by spinning their cocoons with silk and leaves to pupate on the ground. This species is not a pollinator; in fact, adult luna moths do not eat at all and only live long enough to reproduce. They survive on stored energy reserves from when they were caterpillars and only live about a week in their adult form. Despite not being pollinators, their lime green wings and long trailing tails make luna moths one of the most beautiful creatures in Canada.
Leave your leaf litter
Leaf litter also provides shelter for overwintering queen bumblebees and many other invertebrates like lace bugs, snails, worms and beetles, who are food for many predators.
Dead leaves, along with bare ground, old stems, brush piles and deadwood, help support a vast diversity of beneficial insects and other wildlife. Bare ground provides access for ground-nesting bees to tunnel underground, while cavity-nesting bees use plant stems and branches or existing tunnels in deadwood for nesting in. In the fall, leave intact flower stalks such as sunflowers, asters, coneflowers, goldenrods and blazing stars to provide birds and other wildlife with seeds to feed on throughout the winter.
How to clean the yard properly for nature to thrive
If you have to clean up, Pollination Guelph recommends waiting until daytime temperatures are consistently at least 10 C to avoid disturbing or destroying overwintering invertebrates and other animals. At this point, perennial stems can be trimmed down to a range of heights between 20 to 60 cm above ground to facilitate nesting sites. Use your leaves and chopped stems for mulching trees, shrubs, perennials and vegetable beds. Once decomposed, the leaves will add rich nutrients to the soil and contribute to a healthy ecosystem.
Instead of spring cleanup this year, consider using this time to observe some of the returning and resident invertebrate wildlife. For example, red admirals (Vanessa atalanta) are some of the first butterflies observed during the spring across Canada. These butterflies are black with orangey-red stripes on their forewings and hindwings, and white spots on the tops of their forewings. They typically migrate south in the winter, although some populations will live in warmer climates year-round. In the spring, they can be found feeding on tree catkins, and in the summer on flowers such as native milkweeds, coneflowers and asters.
Red admirals will also feed on fermenting fruit, tree sap, mud puddles and animal droppings, while their larvae feed on plants such as nettles and hops.
Another harbinger of spring is the mourning cloak (Nymphalis antiopa). These butterflies are dark reddish-brown with a thick yellow border on their hindwings and forewings, and bright blue spots lining the inside of the yellow border. They overwinter in their adult form tucked into tree crevices, log piles and other places that offer shelter. When they emerge from their winter slumber, mourning cloaks enjoy sap from oak, maple, poplar and birch trees — and like red admirals, they will also feed on fermenting fruit, mud puddles, animal droppings and occasionally flower nectar.
Who knew spring cleaning could be a harmful activity for our insect friends?
To learn more about native pollinators and invertebrates, and how to support them through your garden and landscaping practices, visit:
Pollination Guelph: https://www.pollinationguelph.ca/
Xerces Society for Invertebrate Conservation: https://www.xerces.org/
Click here for more scenes from spring across the country. Show us your spring with the hashtag #HelloSpringCBC