By DAVID WASMUTH
For Montclair Local
Since the end of the last ice age, a remarkable phenomenon has occurred in our area, starting every October.
The trees and shrubs turn brilliant colors, then shed their leaves and shower the earth with rich organic material, renewing the soil while providing shelter, food and nesting materials for the local wildlife that has evolved with this process over the millennia.
At least, that was the case until the invention of suburbia, with its ideal of the perfectly manicured lawn. This ideal, along with the more recent invention of leaf blowers and leaf vacuums, has meant that the once-quietly beautiful season of fall is now most notable for ear-splitting noise, gas fumes and clouds of dust as suburban homeowners pay mow-and-blow landscapers to scour their yards of every last leaf in pursuit of this impossible, artificial and outdated mid-century-modern ideal. Humans pay a price in both money and health, but what’s the effect on wildlife? What do we throw away with our leaves?
Impressed by the spectacular fall migration of the monarch butterfly, people are often surprised to learn that most of New Jersey’s pollinating insects, including butterflies and moths, overwinter in place. Many of these find fallen leaves the perfect winter shelter.
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The eerily beautiful nocturnal luna moth is one example. Its pale green wings can reach a span of more than four inches, making the it the largest North American moth. Its hind wings taper off into long graceful tail-like extensions, but when spread for flight, these wings also reveal a spot on each side that look remarkably like a pair of eyes.
The adult luna moth is also notable for having no mouth. All eating is done as a caterpillar, which feeds on the leaves of host trees including walnut, sumac, hickory and birch. Their numbers are not large enough to damage the trees, but luna caterpillars are a nutritious food source for nesting birds.
In its week-long adult lifespan, the luna moth focuses on mating and producing eggs; food would be a needless distraction. Waiting until after midnight, the females emit powerful pheromones, attracting males over great distances. Up to three generations can be born in a year, but it is the season’s last generation that depends on autumn leaves.
Sensing the shortening days, the caterpillar wraps its cocoon in leaves and falls to the ground with the falling leaves. There, suspending further development for the winter, the cocoon rests, disguised in the leaf litter until spring — or until it is blasted away by a leaf blower.
Joining the luna moth cocoons in your fallen leaves are fritillary butterflies, but these overwinter as caterpillars. There are around 30 different species of fritillaries in North America, the most noticeable one being the dramatically named great spangled fritillary. Fritillaries have a special connection to New Jersey since their only host plant — the only plant their caterpillars can feed on — is our state flower, the much-underappreciated violet.
With their pretty orange and black-checkered wings, fritillaries are common sights in local gardens over the summer — for, unlike luna moths, they are active in daytime and have mouths to feed on the nectar of flowers. The female fritillary also uses pheromones to attract males, but having the leisure of a much longer lifespan than a luna moth, she naps for several weeks after mating before laying her eggs. And she does need to rest up, because a single female fritillary may lay up to 2,000 eggs. The eggs hatch in the fall, but the newborn caterpillars nap in the shelter of fallen leaves until violets start emerging in the early spring, unless, of course … leaf blowers. Even in the spring, fritillary caterpillars depend on last autumn’s leaves; their habit is to feed on violets at night and hide in the leaf litter during the day.
These are just two examples of local wildlife dependent on fallen leaves. Other charismatic species that shelter from the cold in leaves include hairstreak butterflies, wood frogs and tree frogs. In fact, leaf litter supports an entire ecosystem, with myriad insects and other invertebrates providing meals for foraging birds in the winter and early spring while gradually breaking the leaves down into the organic material that will enrich your soil. Come spring, birds will also forage in the remaining leaves for materials to build their nests.
So what to do with your fallen leaves? As much as possible, leave them where they fall. Even those that fall on the lawn will tend to blow into hedges or areas with taller ground cover, where they will form a natural mulch and eventually break down into soil. Leaves that accumulate in inconvenient places, such as driveways, sidewalks or corners of the lawn, can be raked — not blown — into areas that need mulching. Some, of course, can be saved for composting.
But none should be vacuumed up and carted away. They are much too valuable both for your soil and for your wildlife.
In “What’s in Your Backyard,” Sanford Sorkin and David Wasmuth alternate writing about the birds and beasts you may see around your house. Wasmuth is a local environmentalist and amateur naturalist. He is a Rutgers Environmental Steward and the founder of the Montclair Backyard Habitat Project. Seen a bird or animal you want to know more about? Write to us at firstname.lastname@example.org.