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Take Care During Fall (and Spring) Garden “Clean-ups”

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The last of the warm, dry fall days are upon us and it seems like a great time to be puttering around the garden. But this time of year is actually not a good time to be “cleaning up”—that is, removing fallen leaves and woody debris from bare soil, pruning standing plants, and making your yard look somewhat like a victim of a gardening magazine makeover. Leaves and other plant material that fall to earth are part of nature’s systems that nurture and shelter wildlife and enrich and protect the soil. Healthy soil has an uncanny ability to not only keep plants thriving, but also store carbon.

Bedtime for bugs
Leaving fallen leaves on soil is one of the best (and easiest!) things you can do to support wild ones such as birds, amphibians, and small mammals in your garden, as well as myriad invertebrates, including bees, butterflies, spiders, beetles, and worms. Leaves and other plant matter are meant to fall to the soil, to provide food for unfathomable numbers of microbes as well as the macroscopic consumers and recyclers that feed on decaying plant matter. Further up the food chain, many creatures—ground-feeding birds, for example—rely on nature’s soil cover to provide for those they need to eat, which they find under leaves and downed wood (fallen twigs and branches, etc.).

A fox sparrow finds dinner under leafy cover.

If we zoom in a bit, we might see small organisms, such as syrphid fly larvae depending on plant debris for a sort of blanket to help them through the cold, wet winter. As things warm up in springtime, some kinds of syrphid fly larvae will consume enormous quantities of aphids and leafhoppers that can harm our edible plants. Adult syrphid files (also called “hover flies” or “flower flies”) are important pollinators: spring through late summer I see quite a variety of them in my garden, probably because I prescribe a healthy dose of fallen leaves on the ground in autumn.

A leafy layer also encourages other pollinators to make it through the winter. For example, as pollination season shuts down and bumble bee workers (females) and males perish, newly crowned bumble bee queens (technically “gyne,” an impregnated queen who has not yet founded a nest but will establish a whole new generation of bumble bees next year) live on. Queens find refuge by digging a shallow tunnel in loose soil—known as a hibernaculum—that’s often tucked under leaf litter. And, many species of lepidoptera (butterflies and moths) overwinter under fallen leaves as eggs, larvae, pupae, or adults. If we disturb their slumber by blowing or raking them away, they and the ecosystem will suffer. Essentially, they and their habitat need to simply be left alone if we want them to grace our gardens and wilder spaces next year.

Western tiger swallowtail pupa, clinging to wood, waits out the winter and spring.

Don’t cut back
Fall pruning isn’t a good idea because it may stimulate a plant to put on new growth, which could be sensitive to the lower winter temperatures soon to come. Another important reason not to prune in autumn is that branches and bark — particularly of native plant species — may support butterfly and moth pupae, (aka chrysalis). Swallowtail butterfly pupae pass the winter attached by thin threads to woody material — disguised as dried up leaves or old bits of wood to fool predators — until the warmer temperatures of spring stimulate their metamorphosis into adults. While some non-native fruit trees do need winter pruning and it’s beneficial to remove diseased and dying annual vegetable garden plants to prevent the spread of disease to next year’s kitchen garden, in all other parts of the yard, if you must prune woody plants, approach it the following spring, being sure not to disturb any nesting birds.

Erigeron speciosus (showy fleabane) seed head. When viewed closely, seed heads can be fascinating in their complexity.

Moreover, although they may look dead, the seed heads of PNW native perennials such as fleabane, fescue, goatsbeard, and lupine provide food for seed-eating birds, while their stems or stalks—pithy or hollow—provide shelter and/or cavity nests for beneficial insects like the wild bees that nest in small tunnels. If you must cut them back to the plants’ bases, do it as late as possible in springtime and, instead of throwing them away, place the cut stems in an out of the way place so that anyone using them to get through the winter won’t be discards and so that they may be used by the new year’s cavity nesters.

And, aesthetically speaking, allowing fading plants to stand during winter provides structure and form. On cold, frosty mornings they can be magically transformed into silvery jewels.

Protect and nourish the soil
Down at soil level, besides providing a haven for overwintering organisms, fallen leaves and woody debris protect the soil, which can degrade and erode fairly quickly from excessive rain, sunlight, and wind. In nature, soil is protected and mimicking the way it does that will help your soil stay healthy. And over many years, leaves decompose into layers of organic matter that feed plants naturally and gently, improve the condition of soil, and store carbon with the help of mycorrhizal fungi. The other day I relocated a plant to a spot in my front yard that’s been collectively accumulating a couple dozen inches of leaves over the past 15 years. To my delight I found the result of their decomposition: A couple of inches of soft, dark, rich organic matter that wasn’t there a decade ago.

Even when we’re being careful, though, it’s easy to cause disturbance. A few autumns ago, as I moved a small amount of leaf litter to another area, I inadvertently uncovered an overwintering queen bumble bee. I felt terrible as I watched her stumble around, obviously weak and awoken from a sound sleep. Luckily it was a warm, dry day and eventually she flew off into the sunshine. But clearly the awakening had been a rude one, because a short while later she returned and burrowed into some loose soil covered by leaves, just a few feet from where she had been. After she was safely underground, I gingerly placed a couple of particularly interesting rocks several inches from her tunnel’s entrance, as well as some oak leaves on top of the soil to remind myself of where she slept.

Moral of the story: The more we clean up and work towards a neat and tidy garden, the worse off beneficial birds, bugs, and countless other life forms will be. If you tend to be a neatnik (like I am), try to catch yourself every time you start moving into manicure-mode and getting overly tidy—especially in the wilder parts of the yard where wildlife may visit or set up house. It just doesn’t make sense to risk losing them for the sake of neatness or to maintain a certain ‘look.’ If you have piles of leaves that have been raked off hardscape or lawn, here are additional ways to use them in your garden.

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Posted on October 31, 2017 by Eileen Stark

An Underappreciated Insect: The Syrphid Fly

Toxomerus occidentalis, female slurping nectar on Erigeron specious (showy fleabane)

Toxomerus occidentals (female), soaking up nectar on showy fleabane (Erigeron specious)

Beneficial in many ways, syrphid flies — also called flower flies — are true flies in the order Diptera, family Syrphidae. Some can be recognized by their ability to dart around as well as hover in the air in one place, wings nearly invisible, as they search for flowers on which to feed—somewhat like a tiny helicopter, but with much more grace (this flair led to their other common name, hover fly). They come in various shapes and sizes (typically 1/4 to 3/4 inch in length); the tiny ones require a hand lens or macro lens to get a good look. And when you do, you’ll be amazed at the beautiful patterns and bright colors that often serve to mimic dangerous looking bees or wasps and fool predators like birds into leaving them alone (but don’t worry, they couldn’t sting you if they wanted to!).

Syrphids in the genus Spilomyia often mimic wasps, with vivid yellow and black patterns and modified antennae.

Multi-functional
Not needing to carry and store pollen for their young (like most bees do) doesn’t prevent them from being extremely important pollinators. Researchers have found that although syrphid flies pollinate less effectively per flower visit, they visit flowers more often, resulting in essentially the same pollination services as bees. And, it’s thought that they may be more tolerant of the landscape changes that we humans insist on, than bees are.

But syrphid flies are not only important as pollinators in gardens, organic farms, and wild areas. During their immature stage, most species that are found in gardens and nearly half of the 6,000 syrphid fly species worldwide are voracious consumers of aphids, scale insects, and other soft-bodied pests. In coastal Central California, researchers compared romaine lettuce sprayed with an insecticide and lettuce without insecticide. They found that syrphid larvae were primarily responsible for suppressing aphids in organic romaine lettuce, and called the sprayed lettuce “unmarketable.” Other types of syrphid fly larvae are either (1) scavengers that tidy up ant, bee, and wasp nests, (2) feeders of plant material, tree sap, and fungi, or (3) decomposers that feed on decaying organic matter. To add to their achievements, larvae are reportedly more effective in cool weather (as in early spring) than most other such predators.

Myathropa florea, male. Larvae feed on bacteria at the base of trees or in decaying leaves.

Myathropa florea, male. Larvae of this species feed on bacteria at the base of trees or in decaying leaves.

Life Cycle
Females lay their tiny, elongated eggs singly on leaves—typically near aphid colonies, so food is within reach—and they hatch in a few days. The tapered, grub-like larvae are blind and legless, but the mouths of these aphid-eaters are equipped with triple-pointed darts that enable them to pierce and suck their prey dry. At maturation, the larvae are promoted to the soil to become pupa and, eventually, adult flies. Their life cycle takes several weeks; reportedly three generations per year are typical in the Northwest. Most syrphid flies overwinter as larvae in leaf litter—yet another reason to not remove fallen leaves from soil!

Close encounters
The best way to spot these helpful, colorful little insects in your garden is to move slowly and quietly, and observe carefully. Sometimes all I have to do is pause next to a group of flat-topped flowers (white or yellow ones seem to be their favorites), and within a few minutes one or two will show up to eat (and to dazzle me—in morning sunlight these exceptional little pollinators shimmer!). I’ve photographed nine different species in my small yard, and I’ve just started. Hopefully I’ll encounter many more of these fascinating little flyers in the years to come.

To avoid confusion with bees and wasps, just remember that syrphid flies have huge compound eyes (which help to determine their gender—female eyes are spaced slightly apart while males’ come together at the top of their head); their bodies are sometimes flatter than bees and wasps; their antennae are usually very short; they don’t carry pollen around like most bees do; they have one pair of wings (unlike bees and wasps that have two pairs). The second pair of wings of flies has been reduced to two little knobs called halteres, which can be seen in the photo below. Halteres function like tiny gyroscopes that allow them to stay balanced by detecting and correcting changes in rotation while flying, and enable their zippy acrobatic flights.

Although the mouth parts of syrphids vary between species, allowing different species to access nectar in differently shaped flowers, their typical mouth is basically a retractable extension with a spongelike tip that can soak up either nectar or pollen. The species that have this can only feed on open flowers that have easily accessible nectar. Some species have a modified mouth that allows them to feed at elongated, tubular flowers.

The halteres can be seen at the base of the wings.

Conservation
Syrphid flies have been studied very little in the U.S., but European research has shown that species diversity has fallen in areas of intensive human activity. According to the Xerces Society, in Britain, seven of the 22 flies for which Biodiversity Action Plans have been prepared are syrphid flies. Given the substantial loss of pollinators induced by habitat loss, pesticides, nonnative species and climate chaos, and the profusion of others in danger of extinction, there is a definite need to conserve all types of wild pollinator communities.

Providing for these flies is similar to most other pollinators: A variety of flowers from spring till fall for adults, and appropriate habitat for egg laying, larval development, and overwintering. Attract and nurture syrphid flies with a diversity of native plants that provide a lot of nectar and pollen (females need pollen to produce eggs). In the Pacific Northwest, try yarrow (Achillea millefolium var. occidentalis), stonecrop (Sedum spp.), goldenrod (Solidago canadensis), blue-eyed grass (Sisyrinchium spp.), fleabane (Erigeron spp.), white spiraea (Spiraea betulifolia var. lucida), mock orange (Philadelphus lewisii), and aster (Symphiotrichum spp.). The flowers of chamomile, dill, parsley, and other garden herbs with flat-topped flowers are also very attractive to them, as is the pollen of grasses and sedges that’s often available early in the season. Be sure to allow leaf litter and downed wood to remain on soil to help them get through the winter and to provide food for the decomposer types.

Aphid remedy
If you have an aphid problem on some plants, remember that predatory insects that keep pests at acceptable levels need prey like aphids. Always inspect aphid colonies for syrphid fly larvae before even thinking about control, even “organic” remedies. Use only plain water to spray off aphids (that can’t climb back on), but only if necessary. Never, ever use insecticides, to which syrphid flies and other creatures are very sensitive. Usually, just turning your back is the best thing: One summer a large patch of native bleeding heart (Dicentra formosa) in my backyard was absolutely infested with aphids. I decided to let nature take her course—cheering on the ladybird beetles and birds who flourished with the situation. As the leaves died back (as they do naturally when the heat of summer arrives) I forgot about the aphids. The following year there were scarcely any on the bleeding heart, but I found another species of aphid on nodding onion (Allium cernuum); again I did nothing and nature took care of it. The following year the wild onion and bleeding heart were fine, but the aspen trees were stricken. Yet again, ladybugs, lacewings, and several species of songbirds took advantage of the generous buffet. The following year there were no outbreaks in my yard, at least none that I noticed.

Syrphus opinator (female) on Spiraea betulifolia var. lucida

Syrphus opinator (female) on white spiraea (Spiraea betulifolia var. lucida)

Eristatis male on yarrow (Achillea millefolium var. occidentalis

Eristalis sp. on yarrow (Achillea millefolium var. occidentalis)

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Posted on July 24, 2016 by Eileen Stark

Beyond Bees: The Underappreciated Pollinators

Common ringlet (Coenonympha tulle)
The majority of flowering plants evolved to take advantage of insects, and depend on them (and less commonly, other animals or wind) to fertilize their flowers, facilitate gene flow, and prevent inbreeding. Bees might be the most obvious pollinators, and on a warm summer day it seems flowers and bees were made for each other. Native bees, including the 90% of species native to the U.S. that are solitary rather than social — that is, females create nests and raise their young without the help of any other bees — are considered to be the most important pollinators (move over, European honeybees!) and are invaluable members of natural systems. But other capable pollinators—like butterflies and moths, hummingbirds, wasps, ants, herbivorous fruit bats, and even rodents—share the pollen distribution workload, and offer ecological benefits as well. Less well known are the thrips, beetles, mosquitoes (yes, you read that right), and flies that are actually quite accomplished pollinators. Distributing pollen may be a sideline for them, but they often excel because they don’t take pollen back to their nests, as most bees do.

Thrips go way back—to the Permian period, over 250 million years ago—but get a bad rap because of a few species that threaten crops. Studies show that they are strong pollinators of some plants, particularly early in the season when most other pollinators aren’t around.

The adult ornate checkered beetle (Trichodes ornatus) feeds on flowers such as wild buckwheat (Eriogonum spp.), transferring pollen from anther to stigma.

The adult ornate checkered beetle (Trichomes oranatus) feeds on flowers such as wild buckwheat (Eriogonum sp.) and helps transfer pollen from anther to stigma.

Beetles are particularly important in semi-arid parts of the world and have a highly developed sense of smell. They are expert and essential pollinators, according to the Forest Service, and also were around millions of years before bees appeared. Like many species of birds, bees, and butterflies, beetles are in danger of extinction. The International Union for Conservation of Nature lists over 70 beetle species as endangered. The main threats include habitat destruction, chemical pollutants (e.g., pesticides), displacement by introduced species, and hybridization with other species due to human interference.

Although many flies (order Diptera) are recorded as flower visitors, relatively little is known about pollination by flies, compared to other more obvious pollinators. Many flies are strong pollinators, including syrphid flies (which deserve their very own special post) as well as some tachinid flies, which are the most diverse family of the order Diptera (true flies). As adults, they are flower visitors, feeding on nectar and/or pollen; in their larval stages many species help to control insects that we consider pests.

Suillia spp. attracted to bear grass (Xerophyllum tenax) receives a pollen reward.

Pollination by insects is usually mutually beneficial. Here, a fly (Suillia variegata) attracted to bear grass (Xerophyllum tenax) receives a pollen reward and the flower gets fertilized.

While I’m not advocating the nurture of mosquitoes in your garden (the females do suck blood and can carry disease, after all!), it’s noteworthy that mosquitoes, like all insects, do have a role in natural systems. Their primary source of food is flower nectar (with males eating nothing but nectar) and they buzzily and incidentally carry pollen from flower to flower. Plants like goldenrod (Solidago spp.) use mosquitoes as pollinators, as do orchids of northern latitudes, grasses, and many other types of plants. And they are a source of food for birds, fish, amphibians, spiders, bats, dragonfly larvae, and other animals.

How you can help a variety of pollinators

Within our increasingly fragmented landscapes, gardens that provide pollen and nectar-rich plants—as well as nesting and overwintering sites—can create critical habitat and connections for pollinators and other creatures. No space is too small, and when in close proximity to other larger gardens, natural areas, or greenways that sustain native plant populations appropriate to the region, their value deepens.

◊ Choose natives that occur naturally in your area, or at the very least heirloom ornamentals (rather than newer hybrids that may not provide sufficient or appropriate nutrients that native species do). Some garden herbs like cilantro, parsley, and dill attract some pollinators when allowed to flower.

◊ Avoid nonnative invasive species like “butterfly bush” (Buddleia davidii) that sound good, but aren’t.

◊ Provide structure and layering in the form of native trees and shrubs that provide food, cover and nesting sites for various pollinators.

Syrphid fly (Eumerus sp.) on Sedum spathulifolium, a west coast native.

◊ Plan for continuous flowering, spring through fall. Early spring nectar is particularly important for early-emerging queen bumble bees and other solitary bees, as well as flies and beetles.

◊ Choose a variety of plants that differ in the size, shape, and color of blossoms to attract a variety of pollinators. Arrange perennials in drifts or swaths of at least three of a kind, rather than singly here and there. And don’t forget that trees and shrubs produce flowers!

◊ Stay away from pesticides and other chemicals. Insecticides, herbicides, fungicides, and synthetic fertilizers are particularly harmful to sensitive pollinators. Don’t purchase plants pre-treated with neonicotinoids; if you’re unsure, ask.

◊ Don’t be too neat. Leaf litter, dead wood (tree snags or piles of branches), and other natural detritus provide essential habitat, nesting materials, and overwintering sites for adult pollinators or their eggs, larvae, or pupae. And allow some bare soil for pollinators that nest in the ground.

◊ Grow lepidoptera (butterfly and moth) host plants that provide food and habitat for their young. Find out which species frequent your area and grow the native plants that they need to breed.

◊ Provide shallow water and some moist soil. A shallow pie plate or flowerpot saucer, filled with clean gravel or small rocks allow insects to drink without drowning. Also, butterflies and moths need muddy or sandy puddles to obtain water and nutrients. Add a dash of salt to be sure male Lepidoptera get enough sodium prior to mating.

Please see this post for more detailed info on supporting pollinators in all their life stages.

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Posted on July 20, 2016 by Eileen Stark

10 Great Northwest Native Pollinator Plants for Summer

Bombus vosnesenskii

In honor of National Pollinator Week, let’s zoom in on the bees and other hard-working pollinators whose lives are dictated by weather, season, and the availability of food, nesting habitat, and overwintering sites.

Nature has provided pollinators with unique ways of gathering nutritious pollen and nectar for their young, and they’re enthralling to watch. But bees and other pollinators are in terrible trouble worldwide due to our presence and actions. We can give back to them by growing flowering native plants in our gardens (as well as noninvasive exotics that are especially attractive to bees, like lavender and sunflower) with consecutive blooms from early spring till fall. But don’t forget to provide for them during all their life stages — not just their adult stage — by leaving the leaves, dead wood, and spent flower stalks to make sure they can get through the winter and have habitat to raise their young. And, no pesticides whatsoever!

If you’ve already included some native plants in your yard, you’re well on your way to providing for a wide variety of wildlife. Offering a variety of flower shapes, colors, and sizes, with smaller plants in groups of at least three of the same species (like a big, obvious “Eat” sign) will help provide for many different types of pollinators—from long and short-tongued bumblebees and syrphid flies to hummingbirds, beetles and thrips. Below are some Pacific Northwest native herbaceous perennials and shrubs that offer food for pollinators from early to mid or late summer in the Pacific Northwest, west of the Cascades.

The list is just a sampling (read about others in my book or within my blog’s PNW native plant profiles), and the species were chosen because they naturally occur in large parts of the region, are generally easy to grow, aren’t too hard to find at native plant nurseries (although you may need to call around for availability), and attract their fair share of native pollinators. I’ve listed them alphabetically with some basic care guidelines. Fall planting is best, as winter rains begin. (If you’re reading this in springtime, don’t worry—you can plant now, but you’ll definitely need to keep an eye on their water needs during the first couple of summers, at the very least.)

As always, plan ahead and choose plants that fit your light, moisture, and soil conditions, but also choose those that are appropriate to the natural landscape—that is, look to nearby natural areas and add flora that likely would have grown in your area historically. You can also search for a species’ natural range (to county level) here, or check with your local native plant society chapter or county soil & water conservation district. Growing them with associated species that evolved alongside them in nature will help them thrive. No fertilizer is necessary (although a one-time addition of compost such as leaf compost to the soil will add some nutrients and improve soil structure), but do keep them adequately hydrated until they’re established (2 to 5 years). Enjoy!

◊ Achillea millefollium var. occidentals (Western yarrow): Perennial. 1-3 feet tall x 1-3 feet wide. Sun to part sun. Not fussy about soil; moist or dry (will spread faster with more moisture). Spreads by rhizomes and seed. Flat-topped clusters of white, fragrant flowers bloom nearly all summer. (Not to be confused with the Eurasian Achillea millefolium var. millefolium).

◊ Asclepias speciosa or A. fascicularis or A. cordifolia (milkweed) : Perennial. 2-3 feet tall x 2-3 feet wide. Sun to part shade. Moist, well-drained soil, but can handle some drought when established. Rounded clusters of soft pink, fragrant flowers. Check out the Xerces Society’s info on milkweed of Oregon and of Washington. (A. fascicularis is pictured, right) Asclepias fascicularis

◊ Campanula rotundifolia (common harebell): Perennial. 1-2 feet tall x 1-2 feet wide. Sun to part sun. Well-drained, moist to dryish soil. Spreads slowly by rhizomes or seed. Bell shaped, violet-blue blossoms.

◊ Ceanothus velutinus (snowbrush): Fast growing evergreen shrub. 6-12 feet tall x 6-12 feet wide. Sun to part shade (intolerant of full shade). Rich or poor soil; very drought tolerant. Dense pyramidal clusters of tiny, fragrant white flowers. Occurs mainly at mid to high elevations; check natural occurrence, to county level, here.

◊ Erigeron speciosus (showy fleabane): Perennial. 2 feet tall x 2 feet wide. Sun to part shade. Well-drained, moist to dry soil. Lovely and abundant daisy-like, bluish lavender blossoms go nearly all summer. (pictured below)

Erigeron speciosus

◊ Holodiscus discolor (oceanspray, aka cream bush): Fast growing, very attractive deciduous shrub. 8-16 feet tall x 8-12 feet wide (larger on protected sites, smaller on windy, harsh sites). Sun to part shade (intolerant of full shade). Not fussy about soil; moist or dry. Drought tolerant when established. Lavish, feathery plumes of creamy-white flowers in early to mid-summer. Nice for hedgerows. Controls erosion.

◊ Lupinus polyphyllus (large-leaved lupine): Perennial. 2-4 feet tall x 2-4 feet wide. Sun to part shade (intolerant of full shade). Moist soil preferred but will tolerate short dry periods. Tall spikes of bluish-purple, pea-like flowers. (pictured, right)

◊ Sedum spathulifolium or S. oreganum (stonecrop): Perennial. 1-4 inches tall; spreads slowly. Sun to part sun (afternoon shade is welcome). Well-draining, gritty, lean soil. Bright yellow star-shaped flowers. Nice for rock gardens. Not a ground cover for foot traffic. (S. spathulifolium pictured below)

◊ Symphoricarpos albus (snowberry): Deciduous shrub. 4-6 feet tall x 4-6 feet wide. Sun to mostly shade. Moist or dry soils; tolerates heavy soils. Drought tolerant when established. Tiny, paired, pink, bell-shaped flowers. Eventually forms a thicket. Controls erosion.

◊ Tiaralla trifoliata (foam flower): Perennial. 8-14 inches tall x 1-14 inches wide. Shade to part shade. Spreads very slowly by rhizomes or seed. Needs moist, well-draining soil rich in organic matter. Panicles of white to pale pink flowers bloom from late spring to late summer. More details here.

Sedum spathulifolium with syrphid fly

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Posted on June 16, 2015 by Eileen Stark