When Anna Fialkoff, a program manager for Wild Seed Project, said in a Zoom program for the Native Plant Trust, that five keystone species are needed to create a healthy habitat for wildlife in New England, it set off a childish, competitive reaction in me.
Our yard has only two of the five, and I wanted to run out and buy the other three so our yard would be complete.
Those five keystone species are oaks, which support more than 500 species of butterflies and moths; willows, cherries and birches, more than 400 each; and poplars, more than 300. Fialkoff said she got those figures from Doug Tallamy’s “Bringing Nature Home.”
Our yard has many oaks, and has since we moved here in 1975. It’s the predominant tree in our town, and a few years ago when winter moth caterpillars were decimating oaks, people were advised to plant other species. A tachnid fly biocontrol has reduced the winter moth threat, and oaks are again thriving. I have seen some winter moths this year, but fewer than five or six years ago.
We also have a lot of black cherry – one large tree and a grove of smaller ones – that I discovered only last year.
We don’t, however, have any of the other three keystone trees. And after an hour or so checking catalogs and other sources, I’ve decided we can have an environmentally supportive yard without them. And you could, too – although if you have none of the five, you should get at least one.
It turns out, according to the Maine Forest Services’ “Forest Trees of Maine,” revised in 2008, that willows “are found along streams and ponds.” We don’t have those on our property.
One poplar prefers “low bottomlands along rivers,” although others might fit our habitat.
Five types of birches are listed in “Forest Trees of Maine,” and many birches grow in our town. We could grow a birch, but I’m not sure we could find a suitable spot for it.
Fialkoff said that trees that support butterflies and moths are important not only for the species themselves, but for how they affect other species in the food chain, especially in their caterpillar stage. “Caterpillars are a great, protein-rich food for birds,” she said. “They are like a miniature sausage.”
A cecropia moth, the largest moth in North America, hangs on to a pine branch. In its caterpillar stage, it likes to live on trees, and is especially fond of black cherry trees. Cathy Keifer/Shutterstock
Fialkoff mentioned the Cecropia moth, also known as the giant silk moth. The largest moth in North America, it gets as large as some small birds. It spends most of its almost year-long life as a caterpillar, living in trees, especially black cherries, molting several times and feeding on the leaves. Few of the caterpillars survive the several stages to become moths. And as moths, the insect lives just 10 days.
One other host I found when I researched the subject online is maples. This pleased me because we have several red maples on our property – all were either here when we moved in or self-seeded with no help from us beyond our clearing out their competition. The red maples are my favorite tree on our property. We tapped them to make maple syrup when our children were young. They aren’t as productive as sugar maples, but they do produce syrup. The leaves are beautiful and drop early – unlike our oaks and the evil Norway maples on our neighbors’ properties – and they are thin, so they decompose quickly.
I was surprised that maples were not among the five keystone species, and I asked Fialkoff about it. They are a valuable and important species, she agreed, supporting more than 300 species of moths and butterflies. Her answer confirmed my decision not to run out and buy a birch.
Despite its spot as the top keystone species, I have a love/hate relationship with oaks. Yes, they are stately and handsome, but if my wife Nancy and I didn’t spend many hours each year weeding our gardens, both ornamental and vegetable, the oaks would overtake the gardens. During a single afternoon of weeding, we can weed more than 100 sprouted acorns, especially after the high acorn crops of the past two years. This year’s crop has been much smaller, thankfully, although the acorns themselves seem to be larger.
During her talk, Fialkoff talked about more than big trees. Think of garden design in layers, she told listeners. Plant tall trees as one layer, shrubs (including small ones such as native viburnums and serviceberry, aka Amelanchier) as the middle layer, and perennials for the layer closest the ground. She suggested herbaceous perennials, such as milkweeds, coral honeysuckle (which supports hummingbirds), asters and goldenrods.
Let me return to trees to close. Our neighbor Kathy Tarpo, who is horticulture instructor at Portland Arts and Technology High School, pointed one out to me last spring. I hadn’t noticed it before because it is surrounded by oaks, and it’s either on our property line or on the neighbor’s property – which is OK because nature doesn’t recognize property lines anyway. It’s the shagbark hickory, which supports more than 200 moths and butterflies, less than half of what oaks do. But the nuts are edible, and non-moth wildlife loves them. Plus this human loves the way the tree looks.
Tom Atwell is a freelance writer gardening in Cape Elizabeth. He can be contacted at: tomatwell@me.com.
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