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Check out my book, The Sustainable-Enough Garden, available on Amazon, and the book's web site at www.thesustainable-enoughgarden.com. See more plant photos on Instagram.

Sunday, October 11, 2020

Getting by without rain

In late July I blithely congratulated myself on watering less, assuming that rain would come and my plants would be refreshed without supplemental irrigation. My expectations were way off. In the month of September, we got less than an inch of rain. So far October is just as dry.

The garden is drooping

    During the drought, I’ve had to make difficult decisions about watering. I’m finding out the hard way which plants can tolerate sustained dryness. For container plants, it was easier to know what to expect. In hot weather, they wouldn’t last more than a day or two without watering, because the small volume of growing medium in the pot dries out so fast. Those I kept watering with the hose wand or watering can.


    Then there were newly planted perennials and shrubs. Before the drought, I optimistically planted in new areas. When we replaced a rotting stockade fence with chain link last fall, I planted a row of evergreens. In spring I added a buttonbush (Cephalanthus occidentalis

 

The buttonbush has survived so far

and moved a chokeberry (Aronia arbutifolia) to a sunny spot nearby. Around the garden pond, I planted native perennials for pollinators: false aster (Boltonia asteroides), northern blazing star (Liatris novae-angliae), wild bergamot (Monarda fistulosa), and mountain mint (Pycnanthemum muticum). All these will need supplemental watering for their first two years. I’ve kept at it with the watering can.

 

Northern blazing star at the end of its first season
 
    For the rest, it was survival of the fittest. The lawn completely surrendered. With our dog and her friends racing around on its parched surface, the grass wore away completely. Luckily, turf grass is my least favorite garden plant. It should grow in cool, damp environments like the British Isles, where it belongs.


So much for the grass

    In the drought, it’s easy to see the advantage of protective adaptations like waxy leaves. The boxwood (Buxus sempervirens) hasn’t batted an eye. The vinca (Vinca minor) groundcover in the front yard is starting to droop after two full months with no water at all, but it’s still green—another reason I’m glad it replaced the former front lawn.

Vinca has proven very tough

But some waxy leaves of a few evergreen shrubs are turning yellow or brown, as on the Catawba rhododendrons (Rhododendron catawbiense) and mountain laurels (Kalmia latifolia).

 

Rhododendron leaves yellowing
 
    Softer deciduous leaves are drooping. Even the Canadian wild ginger (Asarum canadense), which is usually impervious, has flopped to the ground. 

 

Wild ginger has collapsed
 

In contrast, the goldenrods (Solidago spp.) and asters (Symphiotrichum spp.) are unfazed.


Goldenrod dealing with drought

     I notice that some perennials with fleshy roots have an advantage. Smooth Solomon’s seal (Polygonatum biflorum) is still holding up its leaves. In the cutting garden, the cosmos (Cosmos bipinnatus) has turned completely brown, but dahlias are going strong. Presumably rhizomes and other fat root forms store water for hard times.

 

Smooth Solomon's seal has fleshy roots
 
     I find myself wishing that some of the rain flooding the Gulf Coast would come our way. We’re supposed to get some remnants from Hurricane Delta next week. May it be so! At this point I’ll only believe it when I see it, because so much forecasted rain hasn’t materialized.

 

New England aster holding up well

 

 

Sunday, September 20, 2020

A drop to drink

As our area’s drought continues, wildlife has trouble finding water sources. My garden offers several.

 

Birdbaths offer water in dry times


     Back in 1997, we sank a rectangular plastic fish pond in the lawn and edged it with bluestone. A pump oxygenates the water and circulates it through a biological filter. 

The pond in May

For several years I brought home young koi from the garden center to live in the pond, but they all disappeared in a year or two. Some were clearly pulled out and eaten, possibly by raccoons. Half-eaten bodies were left behind. Other fish just weren’t there the next spring.

Koi weren't making it to this size


     I decided I’d assassinated enough koi and stopped restocking. Now the pond just houses water plants, and I’ve switched to hosting tadpoles. It’s fun to see them grow into tiny frogs that like to sit on the stones beside the water, jumping in as footsteps approach. 

 

Frogs are fun, and they eat insects


    Meanwhile, the pond provides drinking water for wildlife ranging from birds to squirrels to our dog Lola, who likes to wade in and pull out floating plants. Birds perch on the netting that covers the pond in winter to keep falling leaves from settling on the bottom. In this way they can walk across the pond to drink, safe from heavier predators.
 

    I’m pleased that toads have taken up residence in the garden, because they’re prodigious insect eaters. Toads are actually a kind of frog, and they too need to start their life cycle as eggs and tadpoles in water, so the toads I’m seeing may have been born in the garden pond.

 

A well-camouflaged toad
 
     Specifically for birds, I maintain other water sources as well. There’s a stone birdbath at the base of a redbud in view of the kitchen windows. The basin kept falling off its pedestal until I built a brick base for it, fearing that some small animal would be crushed. A ceramic birdbath spends the summer under a nearby crabapple. Birds approach cautiously, perching on nearby branches before landing in the water and puffing out their feathers for a wash. 

 

Birds like water near trees or shrubs

  Hanging from a spruce branch at the side of the house is a water bottle with a perch for birds. This one allows them to drink without the danger of landing near the ground.

 

A safe perch for cautious birds


     In the hottest weather, I’ve also put a few inches of water in a child’s wading pool to allow Lola to cool her feet. I notice that birds regard this as another larger birdbath. With all this standing water, I have to be careful not to provide breeding ground for mosquitoes. I empty out the water every two days, and each month I drop Bti (Bacillus thuringiensis subspecies israelensis) into the pond. It’s a safe soil bacterium that kills mosquito larvae.


    Friends, I’ve decided to stop posting on a weekly schedule. I find I’m running out of subjects. I’ll continue posting occasionally when a topic comes to mind. If there’s something you’d like me to write about, please let me know. Thank you for being with me over the years!

 


 


 

Sunday, September 13, 2020

A fair exchange

An excellent summary by Anne Bikle in Fine Gardening reminded me that there’s no free lunch in the rhizosphere, the top few inches of soil where most of the biological activity happens. True, lots of soil organisms are at work breaking down organic matter into forms that our plants’ roots can use. 

Electron micrograph of soil microbes-photo Pacific Northwest National Lab

But that’s not a coincidence. The roots offer something in return. Every plant exudes proteins, carbohydrates and fats from its roots. These attract the organisms that help plants get what they need and protect them from diseases and pests.

 

Fungal network associated with spruce roots-photo André-Ph. D. Picard
 
    Bikle’s article was a good reminder to support this process by taking good care of soil organisms in the garden. I checked myself against her three recommendations: leaving soil undisturbed when possible, mulching to add organic material to the system, and growing a variety of plants.


    A few years ago I gave up turning the soil in the vegetable bed with my spade before planting in spring. I’d thought this was a necessary step to mix in amendments such as compost and composted manure and turn under any weeds that had sprouted.


     I stopped all this digging when I learned it was counterproductive. I was breaking up soil networks, killing or slowing down soil organisms that were nourishing my plants. I was also churning through organic material by introducing a rush of oxygen into the soil, wasting the compost I added to the bed. 


     I found out it was better to let soil organisms do their work undisturbed. Now I confine the digging to times when I need a planting hole for a seedling such as a young tomato plant. The soil in the vegetable bed has improved. As a side benefit, I’ve got fewer weeds, because when I cut out the digging, I stopped bringing weed seeds to the surface to germinate.

I avoid digging except to plant seedlings

    I’m also making a point of not clearing away leaves that fall on the ground, except on the lawn. I’m still working on striking a balance for fall leaves. I used to chop them up for leaf mulch, until I learned this also chopped up useful insects at various stages of development that were settling into the leaf litter for the winter. For the past couple of years, I’ve mostly let the leaves lie on beds, supplemented by more leaves I drag in from the street that would otherwise go to the city’s composting site. 

 

Letting fall leaves lie
     

     Now I’m missing my leaf shreds. There are places where they’d be especially useful, such as in the newest perennial beds, where the soil could use some quick help. The leaf shreds stay put, not blowing around like whole leaves, and they decompose faster. This fall I think I’ll do some limited shredding to cover those spots.

 
     From Bikle I learned that I’m offering a diverse buffet of root exudates by increasing variety in the garden as I’ve added native plants. That’s because each plant sends out its own recipe to attract organisms to meet its needs. All the better.

 

A mix of native plants: wild ginger, leucothoe, heuchera


 

Sunday, September 6, 2020

Sharing

 At this time of year, the garden starts to look tired and ragged. This week I took the opportunity to reassure myself that chewed leaves aren’t a problem for garden plants. They have lots of ways to deal with chewing insects, and lots of leaves can be chewed without changing a plant’s beauty.


Canadian wild ginger

Humans aren’t that sharp about noticing chewed leaves. Research on aesthetic tolerance has found that 10 percent of the foliage in a garden can be damaged by herbivorous insects before the average gardener even notices.

Insects have been chewing the ginger leaves

     Plants notice, of course, and they’ve evolved a range of tools for turning away hungry animals. First there are mechanical barriers, such as the bark and thorns that some deploy. Without these obvious weapons, though, lots of other plants are ready with chemical defenses.

Closeup shows insect damage

 

Oxeye sunflower

     

 

 

 

 

 

 

     

 

 

We often hear about plants whose tissues are poisonous to leaf-eaters. Milkweeds (Asclepias spp.) can’t be eaten by any but monarch caterpillars because their sap contains toxic cardiac glycosides. Foxgloves (Digitalis spp.) poison browsing herbivores with digitalis in their tissues. 


    Other plants can generate chemical responses to browsing insects. Goldenrod, for example, sends out a chemical signal that keeps leaf beetle larvae from eating too much of each plant. A team at Cornell found that a chewed goldenrod plant sends out volatile organic compounds warning the larvae away from itself and its neighbors. The scientists found that the larvae preferred unchewed plants. 


Goldenrod can communicate with plants and insects

     The goldenrod’s chemical message also alerts nearby goldenrods to the danger so they’ll ready their own defenses. Each plant can lose up to 30 percent of its leaves and survive. In response to the chemical signal, the damage was spread out over stands of goldenrod. This seems like a win-win: the plants aren’t mortally wounded, and the insects get what they need.


    So as I walk around the garden noticing damaged leaves on just about every plant, I remind myself that there are enough leaves to go around. 

 

Leaf miner at work on a columbine

And I’m definitely one of those gardeners who doesn’t notice the chewed parts when I shift my attention to taking in the whole plant. Just as well.

 




Sunday, August 30, 2020

Columbines: Johnny-on-the-spot

 Some of the toughest plants in my garden are columbines (Aquilegia spp.). While other plants in a newish bed off the deck have started to turn brown and lose leaves during the current drought, the columbines are holding on.

 

Columbines bloom here in May and June


    I appreciate the way these easy growers pop up around the garden wherever there’s open soil. This trait of filling in where they’re needed has been especially convenient in areas where I’m waiting for slower growers to get established. 


     In the deck bed, I planted a combination of low growers and medium-height mound-formers, aiming for a tapestry of pollinator-attracting plants that would cover the soil densely. That hasn’t happened yet. The bearberry (Arctostaphylos uva-ursi) I hope will eventually form a mat of small shiny leaves is just starting to spread. New native perennials need time to grow wide. While they’re gathering strength, the columbines are helping out. 

 

Columbines in the deck bed in June


     I have lots of young columbines to choose from. In the vegetable garden alone, each spring reveals a selection of new seedlings. It’s a happy spot for them. The rich soil is renewed annually with compost, and there’s little competition in early spring before food plants have filled the space. 

 

Columbine volunteer in the vegetable garden

I can dig up columbines wherever they aren’t needed and move them to where they are. Three have settled in comfortably around those young bearberries.


    I started out with a broad selection of columbines, some blue-flowered or blue and white, some rose pink, some deep plum purple. The combinations of traits showing up now reflect interbreeding between these varieties. Columbines aren’t shy about spreading their genes around.

A later generation


     Since the 1960s, there’s been an effort to categorize plant strategies, the approaches that plant species employ to defend themselves, survive, compete, and reproduce. Columbines have chosen the role of ruderal plants—pioneers in disturbed areas. They sprout where a natural event or human activity creates an opening. They produce lots of seed that drops wherever there’s a favorable place to grow. They grow fast, covering ground quickly. When they’re crowded out by expanding clumps of stronger growers in one area, they move to another. They live short lives, but their offspring take their places so seamlessly that I can’t tell when an older plant dies and a younger takes over.

New columbines bloom each spring


     Claudia West and Thomas Rainer, in their book Planting in a Post-Wild World, recommend leveraging these plant strategies in designing for visually impactful native plant communities. They divide plants into four categories. In the first group are the taller structural or framework plants, from trees to shrubs to large perennials and ornamental grasses. Second are the seasonal theme plants, such as my rhododendrons (Rhodendron catawbiense), black-eyed Susans (Rudbeckia hirta), and asters (Symphyotrichum spp).

 

Native Catawba rhododendron

 Third are groundcover plants such as wild geranium (Geranium spp.), foam flower (Tiarella cordifolia), and barren strawberry (Waldsteinia fragaroides) that control erosion and provide nectar for visiting insects.

 

Foam flower
 
Last are the filler plants, and that’s where the columbines fit in. They fill the gaps. That’s what I love about them.

 





Sunday, August 23, 2020

Green shade

While the weather is hot and dry, I’m thinking about ways to keep the house cool while saving energy. I hope we’ll be installing a heat pump in the next year. That would really help. Until then, I’ve made a modest start by planting a large-leaved vine in front of west-facing windows.

 

Young pipevine on July 4

 
      After weighing native candidates for this spot, in May I spotted an excellent option: pipevine or Dutchman’s pipe (Aristolochia macrophylla, also called A. durior) at the native plant shop at Garden in the Woods. This native of eastern North America is mostly grown for its large heart-shaped leaves. 

 

Pipevine shading a neighbor's house

 The common name refers to its unusual flower, shaped somewhat like a smoker’s pipe. 

Pipevine flower-photo Adam Skowronski
 

Pipevine is the larval host plant for the native pipevine swallowtail butterfly (Battus philenor).

 

Pipevine swallowtail-photo John Flannery

    
    The vine protects itself from leaf-eating insects by storing toxic chemicals in its tissues. Pipevine swallowtail caterpillars are able to concentrate these safely in their own bodies, making themselves and the adult butterflies they metamorphose into poisonous to predators. Monarchs use the same strategy with toxins in milkweeds.

     If I see flowers on my pipevine, it’ll be a bonus. My main goal is for the densely-growing leaves to shade two kitchen windows that get unobstructed afternoon sunlight in summer, heating up the room uncomfortably. The vine should reduce solar gain. As it transpires water from its leaves, it’ll cool the nearby air a bit, forming a cooler layer between the windows and the outside air. 


    For now, I’ve placed the vine in a large planter. It’s a fast grower. Since May, it’s sent out long tendrils that are already covering the bottom half of the windows. This week Steve helped me to put up a curtain rod above the window frames to hang some netting above the trellis I’d installed. 

 

Trellis plus netting to support the pipevine
 

The vine seems ready to spread upward. If it grows into the rain gutter, I’ll have to trim it back with my pole pruner.


     In late fall, I’m planning to cut the pipevine down to soil level and move it into the basement for the winter. During the cold months, we welcome all the solar gain we can get. At this rate of growth, I don’t doubt it can expand to shade the windows anew every summer. If this one thrives, I could cover more of the west-facing wall by adding more containers of pipevine or removing a bluestone paver and planting the cold-hardy vine directly in the ground.


     Years ago I planted a pipevine at the front of the house, hoping to cover a stretch of fence. That vine has never flourished, probably because it’s shaded by the house, a tall oak, and a row of spruces along the lot line, with a Japanese maple getting taller and denser on its other side every year. 

 

Just hanging on in too much shade
 

It’s instructive to see how fast the new vine is growing with a half day of direct sun. I’d say it’s getting what it needs.
 

Sunday, August 16, 2020

August flowers and their visitors

 Another week, another reminder that nature isn’t as simple as we think. I was going to write about pollination syndromes, suites of flower traits that supposedly evolved to attract and accommodate the right pollinators.

 

Meadow rue
Meadow rue

    This idea originated in the 1870s when Italian botanist Federico Delpino observed that certain types of flowers attracted particular kinds of pollinating animals—white sweet-scented night-opening flowers for moths, tubular red flowers for birds, musty-smelling flowers for bats. As the science of evolutionary biology developed during the 20th century, these observations developed into a theory supporting convergent evolution.

 

Fennel


     To explain why diverse, geographically separated plant species developed similar flower shapes, evolutionary biologists pointed to selective pressures from the groups of animals that pollinated those flowers. A plant that needed to attract pollinating bees, for example, would develop flowers that accommodate bees, whether the plant species grew in South Africa or New England.

 

Flat phlox flowers are convenient for bees

 
     This sounds right, and it’s nice to think of plant and animal species co-evolving to cooperate. More recent research hasn’t completely borne it out, though. A 2009 study of plants from six regions around the world showed that most flowers didn’t fit into the classical pollinator syndromes. Researchers also couldn’t predict the pollinators that would visit a flower based on the flower’s morphology. Some plants bank on attracting just one kind of pollinator, but many more are pollinated by a range of animals. Less exclusivity gives a plant population a more reliable chance to reproduce, even if one pollinator species has a bad year, or a bad decade.

 

Tubular flower of hummingbird sage

    Oh well, never mind. It’s still pretty amazing to zero in on the variety of flower shapes blooming in the garden now, despite the heat and drought. A lot of the flowers I’ve chosen recently for pollinators’ sake are daisy-shaped. In this group there are black-eyed Susans (Rudbeckia hirta), oxeye sunflowers (Heliopsis helianthoides), purple coneflowers (Echinacea purpurea), and zinnias (Zinnia elegans). 

 

Like others in the Aster family, oxeye sunflower has daisy-shaped blooms


     I observe these flowers attracting lots of bees and also some butterflies. They offer efficient foraging, because each daisy-shaped bloom is a composite of many tiny flowers, each offering nectar and pollen.


     But that’s hardly the only flower shape around. There are the flat umbels of fennel (Foeniculum vulgare), the spikes of spearmint (Mentha spicata), the prickly balls of globe thistle (Echinops bannaticus), the narrow tubes of hummingbird sage (Salvia guaranitica) and trumpet honeysuckle (Lonicera sempervirens), and the curved stems of goldenrod (Solidago spp.), which hold arrays of miniature daisy-shaped flowers.

 


Globe thistle

     Each of these flower shapes caters to a different group of pollinators. The hummingbird visiting the honeysuckle is at the large and dramatic end of the scale. More flowers in the garden are visited by diminutive native bees small enough to find the nectar in tiny flowers. The blooms offer nectar for a price, forcing pollinators to brush against pollen and carry it along. As a bee dips into the minuscule flowers of a coneflower’s central disc, it carries pollen from one to the next, enabling them to set seed.

 

A bee pollinates a purple coneflower