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

Striking a balance

There’s a tension built into welcoming native insects. I want to host native leaf-eaters, because they’re the base of the food web for the garden ecosystem. They turn the sun’s energy, embodied in plant tissues through photosynthesis, into food for carnivorous animals, including birds and beneficial insects such as ladybugs. But unchecked, they can also defoliate plants and cause an unsightly mess.

Ladybug eating an aphid

    Worldwide, herbivorous insects make up 37 percent of all animal species. If you’re like me, you don’t spot most of them at work. A leaf-eater has to be big and unmissable, like a Japanese beetle (Popillia japonica) or a tomato hornworm (Manduca quinquemaculata), for me to notice it. But although I don’t see them, they’re out there chewing.

Japanese beetle

    In a healthy garden ecosystem, their population is controlled by predators, including birds, reptiles, amphibians, small mammals, and especially other insects. That’s a reason to avoid pesticides. If I kill their prey, insect predators won’t stay in my yard.

     Problems happen when a nonnative insect with no local predators enters the system. In Japan, for example, Japanese beetles aren’t a problem. When they came to North America in 1916, they left behind the insect predators that kept their numbers under control. Nice for the beetles; less pleasant for rosarians. This story repeats with increasing frequency as global trade expands. In my area, we’re seeing native hemlocks (Tsuga canadensis) devastated by hemlock woolly adelgid (Adelges tsugae), another inadvertently imported nonnative insect.

Adelgid egg cases on a hemlock twig

     I’m trying to keep leaf-eater populations in balance by supporting a broad range of insects in the garden. I tolerate some leaf damage and hope it won’t become too obvious. Research into what’s termed “aesthetic tolerance” indicates that 10 percent of the leaves in a yard can be chewed before the average gardener even notices. 

     This spring as hosta leaves poke up and unfurl in shady spots, I’m noticing that several seem to emerge with notches or tears in the leaf margins. Did some insect get to them as they developed underground, or is this just a result of careless steps before their location showed? To me, the hosta leaves are still glorious. I don’t think I’ll be bothered by a few flaws.

Hosta leaves will still be dramatic with a few holes

     Theoretically, native plants should be even more attractive to native herbivorous insects than imports such as hostas. That was certainly my experience when I planted a native maple leaf viburnum (Viburnum acerifolium) in view of the window over the kitchen sink. Within a few weeks, I saw it completely defoliated. 

I’d chosen to add this shrub to the back of a bed to provide food and shelter for native insects. Well, they’d certainly made use of it. I decided to consider this a victory. Interestingly, that shrub was never stripped by hungry insects again. It seems to have settled into its niche, sustaining a few chewed leaves but thriving. So far, that seems to be typical.

Maple leaf viburnum-photo

Joshua Mayer

Pest control without pesticides

It’s nice to hear about solutions for insect problems other than spraying pesticides. I’ve been a fan of biocontrol—introduction of nonnative insect predators to reduce populations of problematic insects—since I was able to stop spraying my trees for winter moth (Operophtera brumata). 

Winter moth-photo Ben Sale

This lucky turn of events came about because UMass entomologist Joseph Elkinton built up populations of Cyzenis albicans, a tiny parasitic fly that kills moth larvae. As substantial fly populations were established, winter moth damage became a non-issue. The parasitic fly attacks only winter moth and doesn’t prey on native insects.

    Since the winter moth success, I’ve learned about another clever use of a specialist insect, Hypena opulenta, a moth native to Ukraine. This moth eats the leaves of black swallow-wort (Vincetoxicum nigrum) a pernicious vine from the same region that’s causing problems in New England and elsewhere. 

Black swallow-wort, a nonnative invasive vine

Among other negatives, swallow-wort tricks monarch butterflies into laying eggs on its leaves, where larvae starve because they can’t eat swallow-wort foliage. Struggling monarchs don’t need this added trouble.

A monarch nectaring on the real thing, native showy milkweeed

    Boston’s Arnold Arboretum started releasing the Ukrainian moths this spring and saw them defoliate swallow-wort significantly in a test plot. Biocontrol is particularly welcome in the case of swallow-wort, because it’s really hard to pull out. Stems break off at ground level and send up new stalks. Some towns have asked Boy and Girl Scouts to pick unripe pods of swallow-wort vines and dispose of them before they can spread their seeds to the wind. This still sounds like a good idea, because the moths aren’t expected to wipe out swallow-wort, just reduce and control its population and spread.

    Meanwhile, scientists at the University of Rhode Island are working to establish the best predators for red lily beetles (Lilioceris lilii) that chew lilies, especially the Asiatic species, into unsightly stumps covered with beetle excrement. They've released three kinds of parasitoid wasps and are achieving some success.

Red lily beetles at work on a lily stem-photo Charles J Sharp

    When I started gardening back in the 1970s, organic gardening guides promoted the idea of companion planting, claiming that interplanting with herbs or annuals would keep chewing insects from damaging vegetable crops. 


    Unfortunately, this conventional wisdom often turns out to be wishful thinking. Thomas Christopher, in a recent blog post, traces the advice back to Ehrenfreid Pfeiffer, an early 20th century soil scientist and advocate of biodynamic gardening. Pfeiffer conducted bogus experiments purporting to show that certain plants were compatible. The idea was picked up and spread by J.I. Rodale, publisher of Organic Gardening. The nasturtiums, alyssum and marigolds I still dot around my vegetable bed originate from this myth. Most gardeners never traced it back to its faulty source.

Marigolds are nice, but they're probably not protecting my vegetable plants

    Christopher directs readers to a reliable review of companion planting by garden designer Robert Kourik. The scientific papers he cites show a more nuanced picture. Many of the usually recommended flowering plants don’t help to defend food plants, but some do attract beneficial insects that can reduce populations of leaf-eaters. Another reminder of the importance of healthy skepticism about gardening advice.

Pillars of the community

With winter approaching, most flowers have disappeared from the garden. One family of flowering plants, though, keeps on giving. Asteraceae, the aster family, competes with the orchids for the most populous of all plant families. Flowers for pollinators aren't the only ecosystem services they offer. Lettuce, dandelions, thistles, dahlias, zinnias, and marigolds are all members of this vast tribe.

 

Black-eyed Susans are in the Aster family

    Most flowers in this family are daisy-shaped, from the tiny flowers of goldenrod to huge sunflowers. An older name for the family is Compositae, because each blossom is a composite of many smaller flowers. What looks like a petal of a daisy flowers is actually an individual ray flower. The central disc, where the seeds develop, can comprise thousands of tiny flowers.

 

The central disc of a daisy offers multiple flowers for pollinators to visit

     Walking around the garden this week, I could still spot the brown and black flower heads of asters (Symphyotrichum spp.), black-eyed Susans (Rudbeckia hirta), coneflowers (Echinacea purpurea) and oxeye sunflowers (Heliopsis helianthoides), all North American natives in the Aster family. Flowers of sneezeweed (Helenium autumnale), another cousin, were still bravely opening after a hard frost earlier in the week. I aim to have something blooming for foraging insects throughout the growing season, but this perennial’s performance exceeds expectations.

Sneezeweed flowers opening

    It’s good to have these Aster family members in the garden because they offer a lot to insects and birds. The Lady Bird Johnson Wildflower Center recently zeroed in on the contributions of sunflowers to Texas’ ecology. Sunflowers don’t just provide plentiful nectar and pollen for pollinators and beneficial insects. Extrafloral nectar exuded from stems attracts ants. Beetle larvae over-winter in sunflower stalks. Even wide sunflower heads benefit wildlife by providing cover for quail and grouse chicks learning to forage for food.

Sunflowers offer both food and shelter for native insects-photo Pudelek

    Sunflowers may still be blooming in Texas. Here the blooms are gone. Massachusetts has fewer native sunflower species, but in the cold months it’s easy to observe birds feeding off seeds of daisy-shaped flowers of Asteraceae. In my yard, they like oxeye sunflower seeds and the fat seed heads of coneflowers. I haven’t seen any goldfinches lately—they’re not frequenting my thistle (nyjer) seed feeder--but if some stop by this winter, I hope to see them perching on the coneflower heads I’ve left standing.

    Of course, the Aster family isn’t exclusively altruistic. I notice how good the flowers are at recruiting passersby to transport seed to new locations. A pappus, a hairy or bristly structure, surrounds each fruit and helps it attach to fur or clothing or be wafted by the wind. Picture a dandelion head that releases its seeds to the breeze.

It's easy to see how thistle seeds hitch rides

    I’m determined to grow some annual sunflowers to maturity one of these years. So far my seedlings have consistently been bitten off at soil level before their stems get woody. I blame squirrels. 

A futile attempt to protect a sunflower seedling

I have a “pest-control pop-up,” a 3-foot tall tent made of fine mesh fabric on a flexible frame, that I hope to deploy next spring. Maybe if I sow the seeds and cover the area with the well-anchored tent, I can foil the dastardly sprout-eaters. Hope springs eternal.

A bit of progress on neonics

This week I planted a sunflower that I’d bought at Home Depot. My reason for shopping at a big box store instead of a local garden center was the progress Home Depot has made toward phasing out neonicotinoid insecticides from their plant offerings.

Sources of neonic-free plants can be hard to find

    Thanks to a campaign by Friends of the Earth and others, Home Depot yielded to pressure and promised that plants they sold would be neonic-free by 2019. Neonics are systemic pesticides that are used to promote growth and keep plants on retail benches looking fresh and unchewed. The problem is that they also kill or disable bees and other pollinators.

Neonics can kill bees that visit treated plants

     Once a seed or plant has been treated, neonics persist in plant tissues for years and can even be transmitted to nearby plants through soil and water contamination. In 2014, Friends of the Earth found neonics in more than half of bee-attracting commercial nursery plants bought at a broad sample of garden centers and big box stores in the United States and Canada. 

    As they worked on purging neonics from their supply chain, Home Depot took the interim step of labeling neonic-treated plants they sold. 

Home Depot's spin on neonic labeling

They got some negative responses to this practice, because it raised awareness of the danger. Meanwhile, other sellers continued selling treated plants without the warning. This year Home Depot says that 98 percent of the plants they sell are untreated. They attribute the remaining 2 percent to state regulations requiring neonic treatment of certain plants. 

    Meanwhile, I’ve failed totally at growing sunflowers from seed in my garden. When I plant seeds, something bites off the seedlings as they emerge. I imagine this is a squirrel who likes the taste of sunflower sprouts. I’ve tried starting the sunflowers indoors and transplanting young seedlings to the garden. These young plants too have been irresistible to hungry wildlife. That’s why I decided to buy a husky sunflower whose stems are already tough enough to withstand squirrels’ teeth. 

    I bought what was offered: ‘Sunfinity,’ a hybrid that grows to only 3 feet and produces multiple 3- to 4-inch flowers through the season. This plant won’t offer seeds for the birds. It produces nectar for beneficial insects, but it’s sterile, with no pollen. 

Sunflower 'Sunfinity'

This is not the sunflower of my dreams. I’d envisioned something taller with a few dinner-plate-sized blooms packed with seeds. Planting so late, though, I’ve got a chance of seeing the flowers bloom.

    When I encountered the plant, it was showing some flowers. I took care of that by planting it in the vegetable bed, where something quickly bit off the young blooms. 

Stripped

 Undeterred, the plant put out some more buds that are now opening. I imagine that this back and forth will continue into the fall.

Trying again

    I wish Home Depot offered some unhybridized sunflowers, straight Helianthus annuus. Those would do more for pollinators and birds in the garden. But I’m glad to know that my Sunfinity is neonic-free. There’s no point in a pollinator garden that kills pollinators.

First do no harm

Squeezing in native plants

When I read Douglas Tallamy’s book Bringing Nature Home, I was inspired to add native plants to my garden to support native insects. There was just one problem. My garden was already full.

    As a gardening beginner, I chose plants without thinking about their environmental role. By planting what I liked and could get to grow and bloom in my yard, I ended up with a mix of natives and imports. I’m fond of the nonnatives that have settled in successfully, and I had no intention of booting them out.

Doublefile viturnum isn't a native, but I love it

    Instead, I started looking for places to shoehorn in some new plants. Sometimes I could open new areas to cultivation, as by subtracting lawn or removing colonizers such as tawny daylily (Hemerocallis fulva) that didn’t appeal to me. 

Tawny daylily, native to Asia, pops up everywhere-photo A. Barra

More often, opportunities arose when something I’d planted didn’t make it. 

    One chance to add sun-loving natives came when we took down a white-flowered redbud (Cercis canadensis f. alba) that had become ungainly. Daylilies I’d planted nearby when the tree was small had stopped blooming as it cast more shade. Without the tree, they took heart and sent out flowers the next summer. Around them there was space for threadleaf coreopsis, or tickseed (Coreopsis verticillata), which has gradually spread along 10 feet of border, weaving around the perennials and low shrubs in the bed. 

Native threadleaf coreopsis coexists happily with daylilies

The tickseed is a native that draws insects to the area. Behind it, I scattered seeds of common milkweed (Asclepias syriaca). My reason for introducing this possibly aggressive spreader was to attract monarch butterflies, which need milkweed leaves to feed their caterpillars.

I hope monarchs will lay eggs on this common milkweed

    When I planted some dwarf trees around a garden pond, I chose Colorado blue spruces (Picea pungens) for two of the corners. Native to Massachusetts? Well, no, but they’re native to North America, and they provide shelter for moths and butterflies during the summer. I’ve since learned to check a plant’s native range more carefully.

Blue spruce fits in nicely around the pond

    Several native flowers moved in when I converted half of the vegetable garden that was too shady to produce food into an insectary bed, a pollinator garden that also offers benefits for beneficial insects and native leaf-eaters. There I can grow native perennials that are comfortable with part shade. Two kinds of milkweed (Asclepias incarnata and A. tuberosa), oxeye sunflower (Heliopsis helianthoides), garden phlox (Phlox paniculata), black-eyed Susan (Rudbeckia hirta), and purple coneflower (Echinacea purpurea) mix with pollinator-friendly annuals not native to New England, such as zinnias (Zinnia elegans), sweet alyssum (Lobularia maritima) and cosmos (Cosmos bipinnatus).

Insectary plants offer food and shelter for native insects

    A new perennial bed off the back deck offered lots of space for sun-loving natives. That’s a story for another day. Meanwhile, the sad decision to cut down our hemlocks (Tsuga canadensis), native evergreens that were under attack from a nonnative insect, opened up a back corner of the yard. I’m adding native shrubs and perennials there, seeing which ones will take hold with a minimum of watering. That may develop into the garden’s most authentic New England thicket.

Allegheny spurge, a native pachysandra, getting a foothold at the back of the yard

 

Leaving the leaves

Last fall I departed from past practices and let fallen leaves lie on all my garden beds through the winter. The reason for the change was a new recognition that this would help native insects make it through to spring. As the weather warms and daytime temperatures stay moderate, I’m having the first opportunity to assess how this worked out.

Bloodroot emerging from last fall's leaves

    Years ago, I tried using whole leaves as mulch to improve soil in the front yard. I soon recognized that this was an un-neighborly act, because the leaves blew off our property and ended up on other people’s carefully raked lawns. This blunder led to the purchase of a leaf shredder. Shredded leaves stay put. I used them as mulch for about 20 years. 

Shredded leaves make nice mulch and don't blow around

    Then I learned that by chopping up the leaves, I was probably also chopping up desirable insects. Some dormant adult insects spend the winter hiding among the leaves, and others lay their eggs there. If I let the whole leaves lie through the winter, the eggs could hatch and adult insects could emerge when the weather warms in spring. 

Beneficial lacewings can winter in leaf litter

Those emerging insects would contribute to a healthy balance of insect populations in the garden. That’s why last year I not only let leaves that fell on the backyard beds lie un-shredded. I also dragged in as many leaves as possible from my block and a neighbor’s lawn. All those brown leaves are now lying on my garden.

    I’m still working out this system. My approach this spring is to rake the top layer of fall leaves gently off perennial beds. New shoots from the perennials don’t seem to be able to reach the sunlight through mats of undecomposed whole leaves. I see new growth heaving up a section of leaf mulch, and I can’t resist lifting the leaves off to uncover the emerging yellow-green stalks. 

I peeled away the top layer of leaves to uncover emerging perennials

This may be a remnant of an old way of thinking. Maybe next year I’ll have learned that even this careful raking isn’t necessary.

    Around trees and shrub, though, the whole leaves seem to be doing nothing but good. Like wood chips, they’re keeping the soil steadily cool and moist. They seem to be suppressing weeds too, like any good mulch. 

No need to rake away fall leaves that surround trees and shrubs

Tough, leathery leaves from our neighborhood’s red oaks decompose slowly. Even so, they’ll eventually break down and add organic matter to the soil. Like my sheet mulching project, this is essentially a way to let compost happen with less intervention. Instead of moving leaves to the compost pile and then carting them back to the beds after they decompose, I’m letting soil organisms do the work where the leaves fall. Imitating natural processes is a lot less work!

    I do need to move some of those leaves to the compost piles, though, because the bins are pretty depleted. I’ll need some compost to make homemade potting mix. No worries—there are plenty of leaves to spare.

Leaves will help make compost for peat-free potting mix

 
   

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!