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.

 

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.
 

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

    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

 

Fighting fire with fire

 One of the techniques I’m using to control invasive plants in the garden is planting vigorous growers, preferably natives, to claim their space. Invasives love disturbed ground. If I pull them out and leave the soil open to falling seeds or probing roots, I’ll have to do the same job over again. Rather than spending my gardening time fighting off invaders, I prefer to fill the garden with so many successful plants that invasives can’t find a foothold. At least that’s the theory.

    I’m trying this competitive approach to keep out Japanese knotweed (Polygonum cuspidatum). Wherever there’s a patch of bare soil, this highly successful nonnative forms tall thickets that crowd out native plant communities.

Japanese knotweed is the ultimate opportunist

     In my yard, Japanese knotweed pops up along the fence line every year, and I do my best to root it out. This will never be a permanent solution, because no one’s trying to eradicate it from the yards that abut mine. Rhizomes will keep spreading under the fence.
Knotweed multiplies by creating a thick, rapidly expanding mat of roots. If I cut the roots without removing the whole stand of knotweed, I’m actually stimulating more growth.

    This spring I decided to fight fire with fire. I planted a coralberry (Symphoricarpos orbiculatus) next to where knotweed keeps emerging along the back fence.

Coralberry-photo Severnjc

 

This native shrub is known as a suckering spreader. Most write-ups focus on how to keep it in check rather than how to coax it to grow. I’ll encourage coralberry to form a thicket to keep the knotweed from pushing its way into the yard. This summer the young coralberry is slowly expanding, despite being shaded by the fence and some giant pokeweeds (Phytolacca americana).

 

Coralberry guarded by tall pokeweeds

 
     Not all the aggressive growers that I need to beat back are state-certified nonnative invasive plants. Those are certainly a problem, but some of the too-vigorous plants in my yard are natives, such as smooth Solomon’s seal (Polygonatum biflorum). Native plants can range from shy to aggressive too, just like imported plants, as I learned the hard way.

Smooth Solomon's seal taking over

 
     I chose smooth Solomon’s seal because it was recommended for shade. Thirty years later, it’s taken over large areas in the shade of large trees and shrubs. It doesn’t do this in every garden; it’s just found growing conditions in my yard that suit it all too well.

      I’m making a start at reducing the smooth Solomon’s seal population by pulling out its thick storage roots and planting vigorous growers in their place. I’ve had modest success encouraging preexisting clumps of a less-aggressive European cousin, variegated Solomon’s seal (Polygonatum odoratum var. pluriflorum ‘Variegatum’), to take over where the native had been king.

This variegated version is a nice alternative to aggressive smooth Solomon's seal. I'm ignoring the lilies of the valley, also spreading aggressively.

 
     A spreading clump of pawpaw (Asimina triloba), a small native tree, is shading out some of the smooth Solomon’s seal, with the side benefit of producing delicious edible fruit. Under the pawpaw’s shade, smooth Solomon’s seal isn’t sending up so many new plants. Now how to keep the pawpaw from taking over?

The pawpaw is forming a growing patch, worth it for the fruit

,

If butterflies lived here, they'd be at home now

By adding native plants to the garden, I hope to attract more native insects. Sure enough, this year we’re seeing regular visits from pollinators and beneficial insects.

    Gardeners tend to categorize insects as leaf-eaters, beneficials, or pollinators. I used to regard leaf-eaters as a scourge. I’ve changed my attitude now that I understand their importance at the base of the food web, just one level up from plants.

Leaf-eaters provide important ecosystem services

    Plants convert the sun’s energy into carbohydrates through photosynthesis. Leaf-eating insects pass that energy on up the chain. So when I see my kohlrabi’s chewed leaves, I try to remember that the larvae of the cabbage white butterfly (Pieris rapae) that did the damage also provided food for birds and other animals that I want around.

Cabbage white larvae found the kohlrabi

    Beneficial insects are the carnivores that eat leaf-eaters and keep their populations in balance. Some of my favorites are damselflies and dragonflies (Odonata). These are top predators of the insect world, capable of grabbing their prey on the wing because they have the ability, unique among insects, to fly in all directions. 

Virtuoso flyers of the insect world

     Many of the insects I thought were dragonflies are really damselflies, close relatives. At rest, damselflies hold their wings along their bodies, whereas dragonfly wings are held perpendicularly. I’m delighted to notice so many of these beneficial insects around the garden. I’m rarely quick enough to snap their photos, but I relish their bright colors, especially the blues and reds. They often perch on fence posts or flower stalks, like hawks surveying their domain for prey. Damselflies particularly like to eat mosquitoes, so they’re doubly welcome.

Blue damselfly-photo NPS

     I’m hoping that our small garden pond is providing good habitat for dragonfly and damselfly nymphs, the developmental stage before the flying adults. The nymphs live in water for months before emerging on shore, breaking open their exoskeletons, and flying away. I want to witness that someday.

     Among pollinators, we’re thrilled to have been adopted by a ruby-throated hummingbird (Archilochus colubris) that feeds on the nectar of trumpet-shaped flowers near the house: trumpet honeysuckle (Lonicera sempervirens) and hummingbird sage (Salvia guaranitica). Hummingbirds are territorial; males will fight to defend their territory. This one seems to have claimed our deck for his own, and I wish him many happy returns from the migration to his winter home in Central America.

Hummingbird feeding on cardinal flower

     Then there are the butterflies. This week I saw more kinds than ever before. Several monarchs (Danaus plexippus) happened by, checking out the swamp milkweed (Asclepias incarnata). 

Swamp milkweed offers a host for monarch larvae

I’m pretty sure I saw a spicebush swallowtail (Papilio troilus), maybe attracted to a new spicebush (Lindera benzoin) that I planted last year. An American lady (Vanessa virginiensis) alighted on a goldenrod whose flowers are just opening. An Eastern tiger swallowtail (Papilio glaucus) wafted high up among the trees.
 

Spicebush swallowtail-photo Katja Schulz

     I’m increasing my offerings of larval host plants for these butterfly species and also multiplying their nectar sources, the native flowering plants that the adults go to for food. Goldenrods, asters, black-eyed Susans, milkweeds, sunflowers—it’s a banquet for nectaring butterflies.

A Long Dash butterfly? also on swamp milkweed