Working together

Come visit my table at Celebrate Newton, a holiday craft fair, this Sunday December 2 from 10 to 4.

I realize that I’m prone to thinking of the plant world in terms of competition. I suppose this is an over-simplification of Darwinian thought: we picture the garden as a battle for resources where the fittest survive. Experience bears this out when we see aggressive plants-- nonnative invasives but also native plants and imports that happen to be in their best growing environment--crowding out plants that are less well-suited for a particular niche in time and space.

Sweet woodruff ruling the shade garden

    As I learn more about the science of soil and plant communities, though, I find that there’s a lot of cooperation in addition to the competition I tend to notice. The first hint came in junior high, when we were taught the concept of symbiosis through the example of lichens, which, we were told, are a cooperation between fungi and algae. As lichenologist Trevor Goward says, “Lichens are fungi that have discovered agriculture.” The algae provide the fungi with energy through their photosynthesis, and the fungi provide protective structure. It turns out there’s a third partner in this cooperative effort, recently discovered. It’s a kind of yeast.

Lichens are a cooperative effort-photo Alex Proimos

    But there’s more. In The Hidden Life of Trees, forester Peter Wohlleben describes trees as social beings that share nutrients and warn each other of impending danger through their roots. Teaming with Microbes, a fascinating and useful book by Jeff Lowenfels and Wayne Lewis, describes the soil food web, the network of soil organisms that work together to provide plants’ roots with needed nutrients. Each soil organism has something to gain in the complicated transactions going on in the top few inches of soil.

Soil microbes-photo courtesy of Pacific Northwest National Lab

    Fungi called mycorrhizae grow in symbiosis with roots, providing water and nutrients in exchange for carbohydrates made by leaves. Free-living fungi, bacteria, nematodes, protozoa, small insects, and earthworms all seek food for themselves and, as a byproduct of their labor, provide food for others in the network. Each organism has evolved to play its part. It’s interesting that evolution has favored cooperation in this system, not just competitive success.

Fungi play an important role in decomposition

    Above ground there are similar processes at work. When we plant perennials, we tend to think they need plenty of space so they won’t have to compete for water, sunshine, and nutrients as they get established. 

Perennials spaced out for traditional planting

A newer, more natural way of planting recommends closer spacing of different kinds of perennials to form plant communities.

    Some perennials grow upright and tall, others make wide rosettes of leaves or hug the ground and weave their stems between taller growers. Some have taproots that grow straight down, many others create a mat of slender root fibers. Some take off fast in newly open ground, others grow more slowly but persist longer. 

Perennials with different growth habits can grow close together

By working around each other in space and time, the plants get what they need and also help each other by providing shade, edging out intruders, and holding moisture in the soil. In community there is strength.

Before the freeze

Come visit my table at Celebrate Newton, a holiday craft fair, on Sunday December 2 from 10 to 4.


Despite interruption by early snow, I’ve spent the past week hurrying to prepare the garden for winter. A list of chores always looms as the light for working outdoors shortens and the ground gets ready to freeze.

Snow already! Time to rush through the last garden tasks

    Number one on the list is gathering in as many fallen leaves as possible and spreading them around the garden. This fall I’ve reverted to shredding leaves to mulch the new perennial beds at the back of the house. I’ve been shredding less since learning that whole leaves shelter insects and other animals through the winter. 

Letting whole leaves lie for shelter

Last spring I found I had to peel back layers of whole leaves I’d piled on these new beds to uncover the emerging young perennials below. That would have been OK, but once those leaves were gone, there was no mulch left on the bare soil between plants. The thin layer of bark mulch I'd applied when I planted the new perennials had long since decomposed. Until the plants grow to full size, I think they'll need some shredded leaf mulch.

     Everywhere else in the yard, I’m piling up whole leaves. My neighbor Pat kindly donated her bags of raked leaves. I go out periodically and collect leaves from nearby sidewalks and gutters, piling them on a tarp to drag into the backyard. 

Precious cargo

At this point, the drifts of fluffy leaves look way too deep, but I know they’ll settle to a reasonable layer of a few inches as the winter comes on.

    I’d hoped to use potting mix from the large pots that hold my container plantings to layer on top of the grass where I’m planning to enlarge a bed. Cold weather came too soon, though. Starting that new planting area with layers of cardboard, wood chips and compost will have to wait until late winter, when some tree pruning should provide me with a big pile of wood chips. 
  
    Frost reminded me to move hoses and watering cans into the garage or basement. 

Time to put away the hoses

The last job of all will be to wash the large ceramic and plastic pots and move them indoors. Freezing and thawing outdoors through the winter shortens the lives of pots and hoses. I eventually store all the pots in the basement but never get around to washing them until the garden is completely dormant.

I'll wash ceramic pots and store them in the basement--eventually

    A few end-of-fall tasks prepare for indoor gardening. I sifted finished compost from one of my piles, transferred it to a bucket, and ferried it into a large plastic garbage bin in the basement. There it’s available to mix with coir—coconut fiber--for making homemade potting mix. I’ll use that to proselytize for moving beyond peat-based potting mix, giving out little sample bags when I visit garden clubs.

    Saturday I picked out amaryllis bulbs at the garden center. With compost and coir in the basement, I’m ready to pot those bulbs in peat-free potting mix. We’ll enjoy their giant flowers in the warm kitchen while winter rages outside.

Amaryllis flowers light up the dark months-photo pizzodisevo

New perennials the easy way

To share purple coneflowers (Echinacea purpurea) with students in last month’s sustainable gardening course, I asked them to snip off the spiky brown heads of the coneflowers in the flower bed. Just drop those dried-up brown items on the ground, I confidently told them, and they’ll plant themselves.

    The reason I believed this would work was that the same method had succeeded for me. I’d purchased and planted a single potted coneflower. When I wanted to make more, I initially thought I’d have to divide the plant, cutting out a section of its stems and roots. Or I’d have to collect seeds, plant them indoors, and grow them to transplanting size under lights. 

Goldfinch feeding on coneflower seeds

    But there were so many of the “cones,” that I decided to try dropping some where I wanted new plants and see if something would grow. This worked surprisingly well, and now I have a line of coneflowers where I scattered those seeds. 

A patch of coneflowers has grown where I dropped seedheads in fall

The round seedheads are what’s left after the flowers are pollinated, seeds develop from each of the mini-flowers in the central globe, and the petals drop off. If pollinators are around to do their work, each cone can carry hundreds of seeds.

Each spike is a coneflower seed

    Some native flowers grow easily from scattered seeds. Black-eyed Susans (Rudbeckia hirta) do this every year in my insectary bed. This plant is a biennial with a lifespan of two years. It performs like a perennial, though, because the seeds that drop from the flowers grow into next year’s flowering plants. If you didn’t know, you’d think the parent plants lived on indefinitely. I write about these plants a lot because they’re among my most successful and lowest maintenance natives.

    Last year I attended a lecture on how to grow native perennials from seed. This is a way to create a genetically diverse plant collection, because seeds combine the genes of both parents. I learned that the process is much more complicated than what I’m used to with annuals and vegetables. Some perennial seeds need a period of sustained cold, which in nature would be provided by winter. Some need alternating warm and cold treatment. Some need help breaking through hard seed coats.

Trillium seeds require several cold and warm seasons before they'll germinate-photo Finetooth

    These perennials have evolved strategies to delay germination until the conditions are right. That’s how they maximize viable offspring and avoid being destroyed by animals or shouldered aside by other plants vying for the same sites and resources. But imitating the sequence of events that triggers germination in many native perennials would be tough, exacting work.

    The alternative is to let the process happen outdoors without intervening. Since I don’t need to produce large numbers of plants, I can let nature do the work. I’ve stopped reflexively dead-heading, removing flowers before they can set seed. I’m hoping that seeds of some of the new native perennials that flowered in my garden this year, including sweet goldenrod (Solidago odora), Stokes’ aster (Stokesia laevis), and blue-eyed grass (Sisyrinchium angustifolium) will surround their parents with the beginnings of small colonies next spring.

Blue-eyed grass flowering in June

Making room for native plants

As we planted daffodil bulbs together, I overheard two fellow garden club members talking about how to refresh the flower choices at a public place we all care about. “Daylilies and hostas,” they agreed. This overheard conversation made me realize that my plant choices have changed significantly in recent years. I’ve become a native plant nut.

Native plants offer fall and winter habitat for wild creatures

    Yes, daylilies and hostas can be counted on to provide attractive flowers and foliage through the summer. They’re tough, and they don’t mind gardeners’ neglect. When I started my garden, I purposely avoided hostas because I thought they looked like cabbages.

Huge leaves are hostas' leading feature

What was the point of a perennial without showy flowers? In the following years, I came to appreciate the large corrugated leaves of clumps of mature hostas, and I planted a number of hostas in my garden. Some have grown into massive shrub-like eminences with leaves as big as those of the elephant ears (Colcasia spp.) featured in my container plantings. Shade gardening calls for desperate measures (and it’s not true that all hostas lack pretty flowers).

    To some gardeners, day lilies are a suburban cliché, but they’ve rescued a narrow sunny bed along our driveway from failure and confusion. I bought a grab bag of mixed colors sometime in the ‘90s, and now they’re pumping out dozens of flowers from July to September in pleasing shades from yellow to dusty pink. They’re not fazed by heaps of shoveled snow in winter nor proximity to baking asphalt in summer.

Daylilies bloom reliably if they get sun, and they come in lots of colors

    So why not daffodils, daylilies and hostas at the front entrance of a treasured building that’s on prominent view to the community? Because now I’d like us to take every opportunity to show what native plants can do. I wouldn’t throw all those beautiful nonnatives on the compost. Heaven forbid! But showcasing some natives can help convince every gardener to include a native or two.
 

New York City's High Line linear park shows how native plants can enhance a designed landscape

That’s the way we’ll restore habitat for native insects and birds. We don’t need everyone to become a native plant purist. I certainly haven’t. But together we can do a lot for native creatures in our ecosystem.

    Many of the classic plants that make up the backbone of American gardens turn out to be natives. I was pleased to learn that among the broad-leaved evergreens we inherited when we moved in, the beautiful mountain laurels (Kalmia latifolia) and the towering Catawba rhododendrons (Rhododendron catawbiense) turn out to be natives. Right now we’re enjoying the bright fall flowers of New England asters (Sympyhotrichum novae-angliae), also natives.

What would fall be without New England asters?

    By choosing the native species in popular plant families, you can have a landscape that serves native creatures and also looks “legible” to traditional gardeners. Instead of those daylilies, we could plant black-eyed Susans (Rudbeckia spp.). Coral bells (Heuchera spp.) can provide striking leaves to fill the hosta niche. Going native doesn’t mean giving up bright blooms or handsome foliage.

Helping more by doing less

The Xerces Society, which works to protect invertebrates and their habitats, has created nine handsome posters to advocate letting fall leaves lie. They’re offering them in printable form on their website to spread the word that leaves on the ground are necessary for moths, butterflies, bumblebees, and many other garden contributors.

    The reason to let leaves lie on the ground through the winter is that so many species use that leaf layer for shelter. Most butterfly and moth species don’t migrate. They need to make it through the cold months in some stage of their life cycle, whether it be as an egg, a chrysalis, or an adult. Bumblebees don’t gather in hives, and they too welcome an insulating cover of leaves over the shallow holes in the soil where their queens spend the winter.

Fertilized bumblebee queens survive the winter in holes in the ground

    I’m working to welcome these insects and many others to my garden: leaf-eaters, pollinators, and the beneficial insects that, as predators, keep bug populations in balance. 

Dragonflies are top predators, useful for keeping leaf-eating insects in check

I’m counting on these native insects at the base of the food web to keep my plants healthy and my garden a welcoming place for birds and other animals. The three pillars of this approach are avoiding pesticides, choosing the right plants, and letting those fall leaves lie on the ground.

It might look messy, but letting leaves lie is more sustainable

    To help out native insects, I’ve completely discontinued pesticide spraying, even for nonnative pests without local predators. That’s to avoid killing off native insects with friendly fire. No insecticide is so targeted that it doesn’t cause unintended casualties.

In the woods, leaf litter is free of pesticides and stays undisturbed on the ground.

    I’m also choosing plants with the insects in mind. Last week students at a hands-on Newton Community Education course in the yard helped plant my latest insect-attracting shrub, a New Jersey tea (Ceanothus americanus), adding more native flowers to offer pollen and nectar in spring. 

New Jersey tea flowers offer premium pollen and nectar

This little shrub will grow into a 3-foot mound and attract butterflies and hummingbirds to its white or pale lavender flowers. 

     I’m looking forward to experiencing New Jersey tea’s spring fragrance. It’s drought tolerant once established, which fits with my efforts to water less. Right now it’s leafless, showing a few of the yellow twigs that will stand out in the winter landscape when it settles in. When next year’s leaves fall to the ground, they'll help insects through the winter.

    I could undo some of the benefits of planting insect-friendly perennials and shrubs by bagging up my tree leaves and setting them out at the curb for yard waste pick-up. 

Insects lose winter habitat when organic material goes out as yard waste-photo Bill Barber

The Xerces Society warns that sending away those fall leaves--or chopping them up with a lawnmower or leaf shredder for mulch—would be discarding or destroying insects and their eggs and larvae already sheltering among the leaves.

    Not shredding leaves for mulch will save a lot of time and energy. I can spend some of that time piling leaves around trees and shrubs that could use some extra insulation. And there’ll be time to cook up lots of schemes for moving plants around next spring. That’s the beauty of a garden. It’s never finished.

Sunlight needed

A friend touring my garden noticed I had planted an Asian pear in a back corner surrounded by tall trees. “Won’t it need sunlight?” she asked tactfully. Exactly right—of course that little tree, now three feet tall, is not going to flourish or produce fruit in the shade.

Does this Asian pear have a future?

I’ve faced this problem since I started this garden 33 years ago. Why haven’t I learned by now not to plant sun-loving plants in the shade?

    Since we moved in, our backyard has been shaded by a line of Norway spruces along the southern edge of the lot. This provides useful privacy. But it also means that the garden’s southern exposure, its best chance at full sun for flowering plants, doesn’t get a full day’s sunlight. 

Norway spruces block the southern exposure

The sun has to rise beyond the level of the spruce tops, now above roof level, before direct sun hits my flower bed along the side of the garage. Right under the spruces, almost nothing will grow at all. 

    There’s more shade from a big oak that stands next to the back corner of the garage and a tall white pine near the spruces. 

So many trees, with the oak towering over them all

I spent several years hopefully planting classic sun perennials such as peonies, irises, and Oriental poppies. They put out floppy stems and wan, undersized leaves, reliable indicators of not enough sun. They didn’t make many flowers, and blooms that did open were small and pale.

    I did finally find a place to plant those peonies in a patch of sunlight, and I enjoy seeing them bloom every spring, although they don’t make as many flowers as they would in an open area with no trees or structures nearby. 

Peonies--so romantic!

Meanwhile, as the garden expanded, I planted more trees I loved, which led over the years to more shade. There’s only so much you can do with impatiens, those stalwart shade bloomers. I have to admit that I’ve continued to push the limits, planting part-shade plants in what’s actually full shade, only to learn my lesson once again about the need for sunlight.

For shade: impatiens, torenia, variegated foliage

 

    When we took down hemlocks to avoid killing native insects by spraying for hemlock woolly adelgid, I saw sunlight and quickly popped in some new shrubs and small trees. The self-pollinating Asian pear is a semi-dwarf that’s predicted to grow no bigger than 15 feet tall and 11 feet wide. Two varieties are grafted to the base, so if all goes well, we’ll have two kinds of pears, one type ripening in August and the other in September. 

Picking pears in the yard would be great

That’s a big if. Any pears that ripen in my yard are likely to be greeted enthusiastically by birds, squirrels, and raccoons.

    Before that, the tree will need to get enough sunlight to be able to produce flowers—no flowers, no fruit. I’m hoping I can get by with pruning back the surrounding older, taller trees to give the Asian pear some space. That may be kind of like asking a tree to grow in an apartment building’s air shaft. 

 

A scurry of squirrels

We’re experiencing a squirrel population surge in northern New England. Wildlife experts say it’s because of a bounteous supply of acorns last year. With lots of food to fatten them up before the winter, more squirrels survived until spring, and they had more babies this spring and summer. Now lots of squirrels are crossing New England highways, and some are ending up as roadkill that highway departments have to contend with.

Squirrels are on the move searching for food - photo Michael Palmer

    This explains trouble I’m having with squirrels in my yard. Gray squirrels are digging frantically in the potting soil around my container plants. It’s worst if they’re newly planted and there’s lots of soil unbound by roots. But the squirrels try out all the pots, even ones filled with established plants. I’m not sure whether they’re searching for food they previously hid or checking out new potential cache sites. The result is damage to plants that I want to keep through the winter, such as a new blueberry bush and some promising young strawberry plants just starting to bear fruit.

Netting to keep squirrels out of pot of strawberries

    Investigating this moment in squirrel history, I learned that the expected density of squirrels in wooded areas is approximately two per acre. It feels as if I’ve got about ten living on my third-of-an-acre lot, although I admit I can’t tell one squirrel from another. Researchers deal with this problem by capturing squirrels and marking them or implanting chips in order to track individuals.

Squirrel research - photo USFWS

    Our yard must be a favorable place for squirrels because we have so many trees. It’s fun to watch squirrels circumnavigating the clearing at the back of the house, running along thin branches and stretching or leaping from treetop to treetop without ever having to leave the top of the canopy. The neighborhood is full of mature red and white oaks, including a venerable red oak in our yard, so we’ve got lots of acorns.

Will there be enough acorns for the squirrels?

    I also learned that booms and busts in squirrel populations are expected and common. In the 17th and 18th centuries, when North America was covered with forest and squirrels inhabited more territory, explorers and naturalists observed estimated millions of squirrels migrating when food ran out due to population explosions. The herds of squirrels reportedly ran for up to 100 miles and swam major rivers, including the Mississippi. Squirrel numbers declined in the 19th and 20th centuries, but periodic migrations continued. The most recent major migrations occurred in 1968 and 1985. What a sight that would be!

Add swimming to squirrels' talents - photo Lindsay Trostle

    Of course, the predictable end of a squirrel population explosion is a squirrel population crash. Without enough acorns to feed all the squirrels, some will die this winter, and the survivors will produce fewer young. Then the population will presumably level off again.

Winter is a hard time for squirrels

    I’m not sure how I feel about this squirrel die-off. While squirrels in general may be a problem for the garden, it’s hard not to think of a single squirrel as a conscious individual with her own reasons to survive. So take some strawberries, squirrels. I can spare them.

"If you prick us, do we not bleed?"