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Sunday, September 24, 2017

A fair trade

Last weekend I attended a plant swap at New England Wild Flower Society. The society invited members to dig up some plants we could spare and bring them to trade with fellow gardeners. This turned out to be a lot of fun.

NEWFS's Garden in the Woods is a fabulous resource in Framingham, MA

    Each participant brought at least one plant, natives preferred but not required. We were each assigned a group number, 1 through 4. The offerings were varied, from garden favorites quite familiar to me to native plants for special locations such as swampy areas. When everyone had arrived and our group number was called, we dashed to the plant tables and each chose one plant. We took turns choosing until the plants were gone.

    I’d brought two wild gingers (Asarum canadense), two white-flowering phlox (Phlox maculatum ‘David’), a white bleeding heart (Lamprocapnos spectabilis ‘Alba’), and a goldenrod (genus Solidago) whose forebears I grew from seed years ago. 

Phlox 'David" blooms in mid- to late summer

     As I placed my offerings on the tables, I realized I’d be embarrassed if nobody chose them—like not being picked at a dance. I was relieved that they all found homes by the last round. Next year I’ll pot some plants in spring so they’ll look more appealing for the swap at the end of the summer.

    I came home with eight plants: a beautiful purple heuchera, a switchgrass (Panicum virgatum), a foxglove, a blue false indigo (Baptisia australis), two blazing stars (Liatris ligulistylis), a showy goldenrod (Solidago speciosa) and an Allegheny monkey flower (Mimulus ringens).

This well-grown heuchera was a prize

Besides a fun “shopping” experience and a chance to meet like-minded gardeners, the swap met two sustainability goals for me. First, I could be sure that none of my fellow NEWFS members had been spraying their plants with neonicotinoid insecticides before bringing them to the exchange. Neonics persist for a long time, but my hope was that these plants were either seedlings from the gardeners’ original plants, or they’d been around long enough to have outlived any pesticides they might have encountered at a nursery when they were young.

Native plant enthusiasts know not to poison pollinators with neonics

    Second, a swap like this gets around the carbon cost of garden center plants. Annuals and perennials we buy locally zip around the globe before they end up in our shopping carts. Growers may buy seeds from importers who source seed all over the world. They use tissue culture products imported from South Africa, Holland, Turkey, and Poland (tissue culture converts tiny pieces of plant tissue into large numbers of genetically identical plantlets). Large plantations in Costa Rica and Ecuador with space to maintain supplies of stock plants send unrooted cuttings for regional growers in the US to root and grow to saleable size.

Plants growing from tissue cultures-photo Daderot

    To produce high-volume annuals like petunias, breeders send cuttings to specialists at a rooting station, for mass production. A broker shopping on behalf of wholesalers or garden centers fills orders with rooted cuttings from multiple rooting stations.

    Unlike these international travelers, perennials from the plant swap really do come from the local area. And they’re free! A good deal all around.

This goldenrod grew up in my yard

Sunday, September 17, 2017

Hell and high water

Photos of Houston afflicted by Hurricane Harvey reminded us of the worst that stormwater can do. It’s been pointed out that Houston’s unrestrained development created a set-up for flooding.

Flooding in Houston

Developers have been building in flood plains and paving over wetlands and prairies, reducing the chance for rain to soak into the ground. Smarter urban planning could have lessened the catastrophic effects of the hurricane.

Wetlands around Houston used to absorb stormwater--photo by Daniel Ray

    Did you know that China is a leader in this environmental area? They’re developing “sponge cities,” engineering ways to keep rainwater for use by water-poor cities, rather than letting it run off.  Besides cutting down on impermeable paved surfaces, they’re collecting rainwater in ponds and tanks and circulating it into the cities’ water supplies, either for non-potable uses or purified as drinking water.

    I hope it never happens, but if we got 50 inches of rain (a year’s worth) in a few days, the amount that fell on Houston, we’d want to let it soak through every possible surface.

Our deck and stone path, wet but permeable

Even without a huge hurricane, it’s better to keep rainwater on your property, because if it rushes down the street, it carries pollutants with it into nearby waterways. Here are some ways we gardeners can make our yards more sponge-like.

•    Make hard surfaces permeable. This is probably the most important change you can make. For us, the driveway is the main impermeable surface. By replacing a section of our asphalt driveway with porous paving material, we’ve enabled water to soak into the ground. 

Water sinks into the darker porous paving

A nice-looking alternative is to make a driveway out of stones with spaces between them where water can soak in. 

Paving stones let water soak through

Spaces between the stones of our new walkway similarly allow water to reach the soil below.

•    Direct water where you want it to go. If you’re an enterprising digger, you can create swales—basically trenches--to send water to your garden beds or to low-lying areas, where it will gradually percolate into the soil. 

Bioretention swale in Seattle during a 100-year storm

David Del Porto, an environmental visionary who designed an eco-friendly house and landscape called the Urban Ark 30 years ago, told me he used this approach to direct rainwater from his roof to the right spots in his vegetable garden, obviating the need for irrigation with purified drinking water. 

•    Plant a rain garden. This is a shallow depression, ideally at the lowest area of your yard, where water can collect and filter into the soil. Plants in the rain garden will soak up water and help purify it. Heavy soils may need to be amended with sand or gravel to make them drain faster in the rain garden; our sandy soil drains fast already.

A rain garden in Leeds, MA--photo U.S. Air Force

I like to think that we designed a rain garden without meaning to, because the land slopes down from the fence lines, making the center of the yard a collecting site for rainwater. I’d still plant a rain garden if I had a place for it. It’s a great excuse for a new planting project.

Sunday, September 10, 2017

Gypsy moth: more complicated than you'd think

While waiting last week for my computer to return from urgent care, I contemplated a talk about biological controls by Joseph Elkinton, a professor of environmental conservation at the University of Massachusetts, that I heard last November. 

Gypsy moth caterpillar

    What Elkinton said about the history of gypsy moth in North America turns out to be unexpectedly relevant. We had a gypsy moth surge in 2016, and this year there has been significant defoliation by gypsy moth caterpillars, especially in southeastern Massachusetts.

Voracious gypsy moth caterpillars shred leaves

    A complicated web of factors influences the gypsy moth population. It all goes back to acorns.

    Gypsy moth (Lymantria dispar), native to Europe, was introduced to Medford, Massachusetts by Étienne Léopold Trouvelot, an astronomer dabbling in silk worm breeding. He thought he could cross the gypsy moths with native silk moths to produce silk in the US. The insects escaped from his home in the 1860s, and over 50 years they slowly established themselves in the wild. They’ve spread as far as Minnesota and North Carolina.

Life stages of the gypsy moth

    Elkinton explained that until 1989, gypsy moths experienced population outbreaks about every 10 years. Throughout the twentieth century, predator insects were introduced in hopes of controlling the gypsy moth population, but none did enough.

Predatory wasps kill caterpillars, but not enough

     Meanwhile, research into the ecology of the gypsy moth uncovered a system of natural controls. Robert Campbell of the US Forest Service found that the white-footed mouse was the most significant predator of the caterpillars, with birds less of a factor.

White-footed mouse, Peromyscus leucopus, in captivity

     Mouse populations rose and fell with the supply of their main food, acorns, which fluctuated with weather conditions. The mice couldn’t expand their population enough to control gypsy moth outbreaks, when caterpillar numbers spiked exponentially.

    Outbreaks were brought to an end by Nuclear Polyhedrosis Virus (NPV), which eventually killed up to 99 percent of the horde of larvae.

    This cycle continued until another accidental foreign introduction in 1989: Entomophaga maimaiga, a Japanese fungus. Infected by the fungus, gypsy moth caterpillars suddenly died all over southern New England.

    So with mice, viruses and fungi controlling its population, why is gypsy moth surging again? The levels of fungus are highest in wet years. Last year’s severe New England drought allowed the gypsy moth population to escape from its fungal control. This summer, caterpillars chomped foliage until June, when they started to die off. Caterpillars examined by Elkinton’s team showed a combination of viral and fungal infections. Wet weather had turned the tide.

    This means, thank heavens, that we don’t have to make the difficult decision whether to spray for gypsy moth.

    The future outlook for New England trees is mixed. Gypsy moths won’t die out completely, and our trees face a number of stresses from drought and other nonnative insect attacks. A tree can survive one defoliation, but repeated losses deplete its energy stores. Elkinton worries about major losses of native oaks, which the caterpillars particularly enjoy. Then what will happen to the white-footed mice?


Sunday, August 27, 2017

Squirreling away acorns for winter

Acorns are falling. I swept the deck yesterday afternoon, and by this morning a few dozen more acorns dotted the surface. They’re a sign that autumn isn’t far off, and for squirrels, they’re the start of the fall harvest.

Red oak acorns

    Gray squirrels are so much part of our suburban surroundings that we tend to overlook their activities. To remedy this, I opened North American Tree Squirrels, by biologists Michael Steele and John Koprowski. Steele and his colleagues and students designed clever experiments to elucidate the feeding behavior of squirrels they found on their campus at Wilkes University in Pennsylvania.

Eastern gray squirrel (Sciurus carolinensis)

    For gardeners who like oaks, it was good news that acorns can be half eaten and still germinate and produce seedlings. Steele noticed that in early fall, when acorns were plentiful and the weather was still warm, squirrels usually ate acorns of white oaks but cached red oak acorns for later. White oak acorns are programmed to germinate in the fall.

Squirrels may pretend to bury acorns in decoy locations

    The red oaks play a longer game. Their acorns contain higher levels of tannin, a nasty-tasting chemical that protects seeds from predators. They’ve evolved to germinate in spring after a necessary cold period. The researchers observed that later in the fall, squirrels started removing the acorn caps to eat just the tops of the red oak acorns, which contained more high-calorie lipids and less tannin. As winter set in, they were willing to eat the whole red oak acorn, tannin and all. Apparently like us, squirrels balance tastiness versus health factors when they choose food.

Health food or tasty treats? It depends on the time of year

    Do gray squirrels remember where they hide their acorns? It was long thought that they didn’t and had to sniff out buried acorns. Lucia Jacobs, then at Princeton University, showed through an ingenious experiment that squirrels found their own cached acorns more readily than those hidden by other squirrels, although others’ caches might be quite nearby. 

Squirrels remember where they hid their nuts--photo by Juraj Patekar

    As a directionally challenged navigator, I’m awed by squirrels’ ability to recover their hidden nuts. Scientists asked whether squirrels were just good at retracing their steps—I can usually do that—and were finding their caches that way. Or were they constructing a three-dimensional mental map that allowed them to locate their hidden acorns? 

    Another of Jacobs’ lab experiments confirmed the latter. If she trained squirrels to find a nut in a maze and then kept the nut in the same location but changed the way to get there, the squirrels still found the nut. They’d retained its location, not just the directions for getting there.


    Although squirrels recover most of the acorns they store, they do serve red oaks by dispersing their seeds. A study of white versus red oak seedlings found that most of the white oaks sprouted close to the parent trees, whereas red oak seedlings appeared three to six times farther from the mature trees, their acorns having been moved by squirrels and other animals. In this way, squirrels contribute to the development of our forests.

Sunday, August 20, 2017

Pollinator-safe container plantings--do they work?

This spring I refrained from filling my shopping cart with brightly-flowering annuals at my favorite garden center. It felt like a deprivation, but I was trying to avoid bringing home plants treated with pollinator-killing neonicotinoid insecticides. 

What I aspire to--the pollinator garden at Locust Grove in Poughkeepsie

This meant changing my approach to container plantings. Now in August the garden is quiet, but the containers are coming into full bloom. It’s a good time to assess how the new approach worked out.

    I’d fallen into a routine of filling large containers with a combination of tender perennials and annuals from the garden center. 

     I carry warm-climate perennials, cannas, elephant ears, dahlias, and a favorite salvia, through the winter by storing them in the basement. Since most of my containers stand in full or part shade, I’d been adding shade-tolerant long-blooming annuals such as impatiens, browallia, torenia and coleus. 

Browallia blooms in shade

I liked the results, but truth to tell, the combinations hadn’t varied much in years. It was high time for a change.

    This year I followed Patricia McGinnis’ suggestion to “shop” in my own garden for perennials to use in the pots. I also found three places in Massachusetts to buy plants that haven’t been sprayed with pesticides: Thomson’s Garden Center in Salem, Allandale Farm in Chestnut Hill, and the horticulture program at a local school, Learning Prep School in Newton. 

Here’s how my containers turned out:

I surrounded Canna ‘Bengal Tiger’ with anise-scented sage (Salvia guaranitica), which just recently opened its deep blue flowers. 

There aren't many flowers as blue as this salvia's

A few marigolds added as fillers have bloomed continuously, adding a bright touch.

Neonic-free marigolds add a pop of color

    My favorite this year is a combination of another canna with an ornamental grass, name unknown, that I bought at Learning Prep. From the flowers (those wispy stalks at the top), I suspect it may be a reed grass (Calamagrostis).

A mystery grass turned out to be a good collaborator

Golden creeping jenny (Lysimachia nummularia ‘Aurea’) is adding a je ne sais quoi as a “spiller” falling over the edge of the pot. Heaven knows there’s plenty of this groundcover in the garden; it’s famous for its imperialistic tendencies.

    In shade, the giant leaves of elephant ears provide bulky focal points. To their pots I’ve added a purple-leaved heuchera for some contrast and offspring from an angel-wing begonia I bought last year that will offer pale pink flowers as the weather cools. 

Contrasting leaf colors and forms complement elephant ears

I doubt the begonia is neonic-free, but I couldn’t bear to throw it away. Japanese painted fern (Athyrium niponicum var. pictum) pops up anywhere shady in the garden. Not surprisingly, it’s willing to collaborate with elephant ears.

Japanese painted fern is an adaptable shade-lover

    Apple-blossom-pink geraniums are doing OK in part shade in the front yard, helping to cover up a not very decorative drain cover that we have to keep accessible. In Salem I found red coleus that’s growing well in a north-facing spot along the driveway.

Coleus without the pesticide spray

    The more I scrutinize the combinations in the pots, the more I can see ways I’d like them to be different. But overall, I’d say that for container plantings, there’s life without neonics.

Monday, August 14, 2017

How it should be done

Yes, a garden can be both sustainable and beautiful. My faith in this ideal got a big boost Saturday when I visited garden designer Robin Wilkerson’s enchanting home garden in Lincoln, Massachusetts. She opened her site to visitors as part of a native plant tour organized by the Ecological Landscape Alliance.

The entrance to Robin's sustainable garden

      Robin’s house and garden sit on old farmland that had been taken over by nonnative invasive plants. For 20 years she has been reclaiming expanding portions of the lot for her organic garden, tearing out unwanted plants and sheet mulching with cardboard and wood chips to smother unwanted vegetation. She grows a large vegetable garden, grapes, berries, and numerous fruit trees.

Beds of bird- and pollinator-friendly shrubs and perennials lead to fruit trees in the background

    Unlike me, she’s resisted planting tall trees that would shade sunny areas. Her flowers enjoy full sun. There’s also a shady woodland section. 

    I had attended a workshop Robin taught at New England Wild Flower Society’s Garden in the Woods on native shrubs for garden use. Her enthusiasm for these plants was contagious and reinforced by a tour of the garden on a lovely June day. Afterward, though, second thoughts set in. 

    Many of the plants she’d showcased had medium-green, medium-sized leaves. They might have pretty fruits and bright fall foliage, but their flowers were often small, off-white, and not very eye-catching. I thought that a garden of these shrubs would look like a typical New England woodland edge, generally pleasing but not particularly striking or ornamental.

    Seeing Robin’s garden, though, I suddenly got it.

A peach tree, ornamental banana, and hanging basket of calibrachoa blend with native honeysuckle and phlox

While supporting biodiversity and welcoming wildlife, she’s combined natives and nonnatives in a harmonious blend of flowering plants from New England and around the world. The natives she’s planted are shown at their best through thoughtful combinations of shapes, sizes, and leaf colors and textures. 

It's all in the design

    She has large, thriving patches of a long list of pollinator-friendly plants. Plentiful fruit beckons to both humans and birds. 


She’s lined the lowest point in the lot, the back border, with a barrier made from pruned twigs and branches; 

This homemade fence provides shelter for insects and other animals

in addition to demarcating the lot line and preventing erosion, this provides a home for insects and other animals. For birds, she keeps several dead trees topped at around 20 feet standing behind the garage. These snags are valuable to woodpeckers and others that feed on insects beneath the bark and build their nests in tree cavities.

Dead trees offer food and habitat for birds

    Insects were everywhere. In addition to the many bees working flowering perennials, butterflies were wafting all over the yard, 

Black swallowtail nectaring on a tithonia flower

and I spotted a hummingbird moth. That was just while strolling around gawking at the flowers; I’m sure closer observation would find that this garden hosts a full range of insects in dynamic balance.

    Robin’s is the kind of garden I aspire to. The visit immediately got me thinking about how to emulate her dense plantings and thoughtful combinations of natives and exotics. Next, the front yard!

Sunday, August 6, 2017

Let it rain

What a lush garden year we’re having! Last summer’s gardens were parched by drought. This summer the Northeast has been blessed with plentiful rain. 

Foliage is thriving thanks to plentiful rain

As of August 6, we’d had 30.83 inches of precipitation in the Boston area in 2017, well above the average of 25.88 inches by this date. You can probably see the difference in your garden; I certainly can in mine.

    Why should that be? What makes rain better for gardens than irrigation? We run a sprinkler irrigation system, so unless I cut back on scheduled watering, my plants should be getting enough water even when it doesn’t rain.

Water beads on a giant elephant ear leaf

    There are limitations to even the best-designed irrigation system. Ours is set up in 12 watering zones. Twice a week, sprinkler heads pop up in the early morning and start spraying in a programmed sequence, controlled by a computer in the basement. A rain sensor prevents watering when there’s been adequate rain. With this system, I lavish a lot of water on the garden, sometimes more than my conscience tells me I should.

    Theoretically every plant gets plenty of irrigation water, but in practice, I’ve learned, it’s not that simple. As the garden has matured, shrubs have grown wide and tall, hogging the spray of water and creating dry shadows behind their bulk. And the arcs described by the sprinklers’ spray don’t fit exactly to every angle and curve of plantings. Inevitably some patches get less irrigation.

    Beyond falling evenly on the whole garden, rain conveys numerous advantages:

Lots of rain is helping this St. John's wort get established

•    Whereas irrigation water contains dissolved minerals, including calcium, magnesium and sodium, rainwater is “soft” and mineral-free. As a result, it pulls nutrients by diffusion from where they're bound in the soil, making them available to plants’ roots.
•    Rain water is acidic, which promotes release of micronutrients including zinc, manganese, copper and iron that plants need. Most of my garden soil is acidic already, but there may be alkaline areas where concrete paving leaches lime. Acidic rainwater is especially beneficial in those spots.

Soil next to sidewalks may be alkaline

•    Rain falls at 20 miles per hour, penetrating soil better than irrigation water, which falls at 5 mph.
•    Rain is saturated with air, so it oxygenates soil. That’s good for plants
•    Rain contains nitrogen in the form of nitrate and ammonium from the air. This nitrogen becomes available to plant roots and promotes growth.

Big canna leaves can use a boost from extra nitrogen in rain

•    Rain doesn’t contain the chlorine that comes with treated drinking water. Chlorine inhibits plant growth.
•    Rain flushes salts (such as road salt) that inhibit growth through the root zone and washes mineral deposits, dust and pollutants off leaves, making for more effective photosynthesis.

The proof is in the pudding. The garden looks happier this year with more rain. 

New plants I added in June and July are surviving, despite the heat. Just watering them might not have been enough if it hadn’t been for well-timed, frequent rain.