Hard choices

A garden club member recently asked me how I would deal with an infestation of gypsy moth caterpillars on a mugo pine (Pinus mugo). Last summer her tree was crawling with them. 

Nonnative gypsy moth caterpillars can cause massive defoliation

Would I use pesticides in this situation? Fortunately gypsy moth populations wax and wane on a predictable cycle. In wet years, like the one we just had, a fungus that kills the caterpillars surges. We can expect minimal gypsy moth damage this summer, so her tree should get a break. Her question raises a larger issue, though. When is it right to use pesticides?

    I was recently disillusioned to learn that the Arnold Arboretum is using a neonicotinoid pesticide to control massively destructive hemlock woolly adelgids in its vast collection of eastern hemlocks (Tsuga canadensis).

White cottony masses on this hemlock are adelgid egg cases

Following the lead of Great Smoky Mountains National Park managers, they’re taking a two-pronged approach to this nonnative pest. They’re spraying the trees with horticultural oil, which smothers the insects, and they’re drenching the soil around the trees with imidacloprid, which attacks their nervous system.

Gray trees in this view of the Smokies are hemlocks killed by adelgids-photo NPS

     In the Smokies, this treatment is reducing adelgid damage and even resulting in regrowth of some hemlock foliage (When it’s not applied to soil, the pesticide is injected into the tree’s bark). Hemlocks are foundational species in the park. Park managers decided that losing them all was unacceptable.

Drenching soil with pesticide-photo NPS

    I sympathize with their dilemma and the Arboretum’s. We resolve to limit our use of pesticides or ban them outright. Then a threat to a plant we can’t bear to lose makes us break our promise to ourselves. As an Arboretum staffer writes, “. . . we are an essential resource for a large urban population that for over 150 years has enjoyed . . . a majestic hemlock-dominated forest.”

Hemlock forest

    The problem, of course, is that all pesticides cause collateral damage. I stopped spraying hemlocks in my yard with horticultural oil for hemlock woolly adelgid two years ago when I realized that even spraying in early spring was killing some insect bystanders that I didn’t want to lose. 

Spraying for adelgids could kill bumblebees and other early foragers-photo Ivtorov

The USDA acknowledges that in the Smokies, imidacloprid affects insects in tree canopies and in the soil at their feet.

    It was human activity that brought the adelgid from Japan to North America. It has no natural predators here. Some human response seems to be needed before all our hemlocks succumb, but what should it be? Applying a pollinator-killing neonicotinoid seems like an unhappy choice. 

     One hopeful development in the Southeast: introduction of natural predators from Japan that eat only adelgids. 

Biocontrol beetle eating adelgids

Tiny beetles in the genus Laricobius have been released in the forest and succeeded in decreasing the adelgid presence without affecting native insects. The hope is that a new balance will develop between these predators and their adelgid prey. Foresters in some areas have been able to stop the chemical treatments. 

     The beetles will never kill every last adelgid, but they may allow hemlocks to survive. Was it worth using pesticides before the beetles became available? I guess so.

Ornamental and proud

Growing “ornamental plants” sounds like a frivolous pastime, doesn’t it? There’s a tendency to rank plants we grow for their beauty lower on some kind of moral scale than food plants or other more obviously useful growing choices. In a September blog post, Susan Harris protests the dissing of ornamental plants, which she prefers to call nonedibles.

Perennial border at Mottisfont Abbey, UK. Beautiful, but is it environmentally sound?

    I’ve definitely gone Susan’s way. Mine is an ornamental garden. I like flowers, and that’s what motivated me to start my present garden. I started out with the goal of having something blooming from early spring through late fall. But my shady lot wasn’t going to support heavily-blooming perennial borders, so I adjusted my aims. Instead of nonstop bloom, I focused on contrasting leaf textures, sizes and colors, with a few shade-tolerant flowers as accents.

Hosta flowers bring a bright accent to a shady spot

    When I read Bringing Nature Home and got on board with growing native plants for native insects, my gardening aspirations changed again. Now I’m trying to make a pretty garden that’s also environmentally friendly and hospitable to native insects. Sure, I’ve got a vegetable bed that struggles to produce because of too much shade. But growing food isn’t my primary motivation. It’s making something beautiful.

Around the garden pond in May

    That doesn’t mean that my fellow ornamental gardeners and I are failing to do our part for the environment, though. Except for providing food for humans, ornamental plants provide the same ecological services as vegetables and fruit trees.

    My yard is sequestering carbon in a major way because I’ve got so many big trees at this point. A tall oak, horse chestnut or pine extracts more carbon from the atmosphere than a smaller cherry or apple tree. And although they're not producing edible fruit, my trees modulate temperature, hold water in the air and soil, and prevent erosion. The soil fungi feeding on rotting leaves and wood chips sequester carbon too.

A horse chestnut provides lots of ecological services

     Beautiful mountain laurel (Kalmia latifolia) and winterberry (Ilex verticillata) foliage cleans the air and converts carbon dioxide to oxygen for us to breathe just as well as utilitarian leaves of corn or tomato plants would. 

Mountain laurel offers beauty and much more

My berm of ornamental trees and shrubs—white pine (Pinus strobus), Colorado blue spruce (Picea pungens), Japanese stewartia (Stewartia pseudocamellia), and mixed juniper and arborvitae shrubs (Juniperus and Thuja spp)--prevents stormwater runoff effectively even though I didn’t plant them for that purpose.

The berm in November

Rain percolates into the soil at their feet, replenishing groundwater instead of carrying debris and chemicals into storm drains and the nearby Charles River.

    Growing a mix of ornamental native plants and imports promotes biodiversity, providing food and shelter for animals, from insects on up. If I only cultivated a vegetable garden, they’d find less support in the yard. As I add more native milkweeds (Asclepias spp), garden phlox (Phlox paniculata), and other flowering plants that feed insects, lots of pollinators and beneficial insects show up to collect nectar and pollen and lay eggs where their caterpillars will find the right food.

A monarch on swamp milkweed (Asclepias incarnata)

    Yeah, I’m an ornamental gardener. Want to make something of it?

Wall! What is it good for?

One of the many reasons that a border wall is a terrible idea: it’s a design for environmental disaster. Living in the Northeast, we picture the Mexican border territory as a barren desert populated with a few cacti and coyotes. That’s not true at all. The southern border lies in a transition zone from temperate to tropical habitat. In Arizona, New Mexico, and Texas, the border runs through sky islands, mountainous areas surrounded by desert.

 Catalina Mountains near Tucson-photo Brambleshire

 Protected by a chain of wildlife refuges, this varied geography makes a home for an unusually rich mix of species. The border region is one of the most biodiverse areas in North America and hosts more than 180 threatened and endangered species. 

    Sections of wall already constructed have caused serious trouble. 

Border fence restricts movement of wildlife

Dividing animal populations that roam between the US and Mexico creates smaller groups with less genetic diversity, leading to extinction. The wall cuts off water access during the dry season. As climate change progresses, the barrier hampers animals’ ability to adapt by choosing the best locations at each time of year. Even low-flying birds, such as pygmy owls, can’t fly high enough to make it over the wall. 

    The 2005 REAL ID Act permits the federal government to forge ahead on wall construction in the name of national security, ignoring existing laws, such as requirements for environmental impact studies. Crews with chainsaws appeared at the National Butterfly Center, a private sanctuary a few miles north of the border, without warning and tore out carefully chosen plantings fostered over many years. 

Fiery Skipper at National Butterfly Center-photo Bettina Arigoni

These losses will be hard to recover, even if sanity does return to our government. Meanwhile, the 24 million dollars it costs to build a mile of wall could fully fund population recovery of endangered ocelots, jaguars and gray wolves that depend on borderland refuges.

Endangered ocelots need to range freely between the US and Mexico-photo Ana Cotta

    The height of Trump’s fantasy wall varies. It’s been as high as 55 feet. In my town, we don’t have any 18-, 30-, or 55-foot walls or fences. The usual fence is 5 feet tall. My yard is surrounded by wooden fencing. 

This fence looked best when it was new and fresh in 1997

When a small dog came to visit, I noticed that in a lot of places, the fence doesn’t reach the ground, making it easy to slip under. Cats and raccoons regularly climb over the top, and squirrels hop across on overhanging branches. Even so, I wish I hadn’t opted for solid fences. Now I prefer the wood-framed fences filled in with lattice or widely spaced wire that I see in a few places in the neighborhood. 

A more open fencing option

This system creates a formal barrier, but it doesn’t keep migrating plants or animals out. It also looks better. The best thing about my fences is the support they provide for clematis vines.

Grape and clematis vines twining up the driveway fence

    Can’t we find a more sensible way to maintain our borders? As California Congressman Ted Lieu said, a wall is first century technology. It’ll kill endangered animals and ruin pristine wildlife refuges, but it certainly won’t keep out refugees who have nowhere else to go.

Monument to people who've died trying to cross into the US © Tomas Castelazo, www.tomascastelazo.com / Wikimedia Commons / CC BY-SA 3.0

Green thoughts in a gray landscape

During a Christmas week visit to New York, I noticed some ways city dwellers bring greenery into their surroundings. People crave vegetation. There were shrubs toughing it out in pots in the front areaways of brownstones, big planters in front of skyscrapers, window boxes, even fake vegetation, such as this plastic sheet printed to make a Brooklyn chain link fence look like a wall of ivy, 

Nice try

and this blanket of artificial turf masking a utility area on Roosevelt Island.

Something must be really unsightly

    I sure miss greenery during the shortest days. House plants help. In addition to cleaning the air and converting the carbon dioxide we exhale into extra oxygen in the house, indoor plants have many demonstrated psychological benefits. They reportedly promote calm, attentiveness and creativity and increase productivity. I’d just say they make winter less depressing and bring life to sterile man-made environments. We weren’t made to live without plants.

Houseplants remind us of greenery to come

    There’s an often-mentioned theory that the reason we surround our houses with lawns is that early humans felt safer in grasslands where they could spot approaching predators before they pounced. This strikes me as possible but completely unproveable, as are many products of the school of thought that attributes the behavior and psychology of modern-day human beings to hunter-gatherer culture earlier in our evolution.

If only he'd had a lawn!-Reconstruction by Mauricio Anton

    Now that the sabre-toothed tigers are gone, we can skip a lot of that lawn and replace it with a more diverse landscape. Even video game designers have gotten past the ubiquitous veldt, endowing their imagined landscapes with lush, region-specific vegetation. That’s what I’m hoping for in my yard. In winter, I’m glad that I planted lots of evergreen shrubs and trees that offer splashes of color in the otherwise drab view from the back of the house. They also provide shelter for wildlife, confirmed as birds pop in and out of the branches.

At least there's something in the yard that's not brown or gray

    As I survey the scene from the back windows, I’m hoping that in addition to the conifers, the thick layer of fall leaves I piled on the beds this fall is also doing good for creatures in the yard. I picture insects burrowed into the leaf litter and sleeping in the flower stalks I left standing. The theory is that lots of beneficial insects will emerge in spring ready to start their work as predators keeping leaf-eating insect populations in balance.

Beneficial lacewing prepares for winter

    Last year in late winter we went south to New Orleans, Memphis and Nashville seeking an earlier spring. We did see some green leaves, 

New Orleans has ferns that don't grow in New England

but I learned what I was really yearning for was the day-by-day unfolding of spring at home. 

     One of the pleasures of tending the same garden space over the years is adding to your store of observations about how it changes through the seasons. I know that winter doesn’t mean an end to all natural processes, they’re just happening where I can’t see them. Roots are still storing nutrients, ready to send them up into new growth in spring. Until then, I’ll crave green things.

Come back soon!