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How to Attract Insects into Your Garden – by HPSO Member Susan Masta

This essay, “How to Attract Insects into Your Garden,” was originally published in the HPSO 2020 Spring Quarterly, under the title “Insects in the Winter Garden.” The gardening practices outlined by author Susan Masta, however, apply year-round and are especially helpful guidance as our gardens are increasingly affected by climate change. A biology professor at Portland State University, Masta promotes biodiversity throughout the seasons in her intriguing Southwest Portland garden. It will be open to visitors on June 4 and 5, 10 am-5 pm, as part of HPSO’s 2022 Open Gardens program.

The sunny yellow flowers of our Hamamelis x intermedia ‘Pallida’ witch hazel light up a gray winter day, and I love smelling their fragrance during breaks in our drizzling rain. This tree retains its dead leaves, however, so I pull off the brown leaves to expose the graceful limbs covered in bursts of yellow, sniffing each flower as I go. I need to take care not to get a fly in my nose, though, as I’ve discovered that our witch hazel also attracts a diversity of flies that feed at the flowers and hide among the dried leaves. This past week, a ruby-crowned kinglet has been visiting the witch hazel each morning, foraging for flies among the leaves. It has been fun to watch this small bird as it flits and twirls among the branches. I think I won’t be taking any more leaves off this year.

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Hamamelis pallida flowers, photo provided by Susan Masta

I manage our southwest Portland garden for insects and biodiversity, although perhaps “manage” is too strong a word. I pull weeds and deadhead flowers, but often I just wander with a cup of coffee and admire the morning’s happenings in the ever-changing garden. It always looks a little wild and rambunctious, but I see beauty in gardens that appear a bit messy, because insects thrive in such places.

To promote biodiversity in our little island of nature in the city, my husband and I maintain a diverse mix of plants that bloom and provide resources throughout most of the year. Insects attracted to flowers typically either sip their nectar or eat their pollen. Bees collect pollen to provision their young. When a bee, fly, beetle, or butterfly moves from flower to flower, it may inadvertently transfer some pollen, thereby pollinating the plants. Without insect pollinators, most flowering plants cannot reproduce, and plants would not have evolved the diversity of colorful, fragrant flowers that we gardeners appreciate so much.

Argia vivida ovipositing in Mimulus. Photo provided by Susan Masta.

When people ask me what they can do in their yards to encourage bees and biodiversity, I often reply, “Do nothing!” This is only half in jest. Insects, spiders, and the myriad other invertebrates that make a diverse and healthy ecosystem need food and shelter to complete the various stages of their life cycles. Thus, in addition to not applying pesticides, it is important to leave areas of undisturbed soil, dead pithy stems from last summer’s flowers, dead trees or logs, and piles of decaying leaves. A well-manicured landscape will simply not support the same biodiversity of beneficial insects that a less-maintained yard will. Because insects are the primary food for most birds, a garden rich in insects is a garden rich in birds.

What happens to all the insects in winter, when stems are bare and few flowers are blooming? Most of an insect’s life is spent as a larva, or juvenile; and for most insects, the larval form differs from the adult in how it looks, what it eats, and where it lives. This is where the messy garden comes in. Insect larvae, being relatively immobile and flightless, need undisturbed areas to shelter in.

Our dragonfly pond is a good example. We leave some leaves and decaying vegetation in the pond at all times, as that is where dragonfly and damselfly larvae overwinter. The gorgeous red cardinal meadowhawks that hover over the pond in the summer spend most of their lives as drab brown larvae, hiding out in the pond muck waiting to grab an unsuspecting insect that swims by. We rarely have mosquitoes in the yard, as the dragonflies devour them all, both in their juvenile aquatic stage and their adult flying stage.

The dragonfly pond. Photo provided by Susan Masta

The essence of summer for me is to amble through the garden taking in its colors, textures, and fragrances and observing the vibrant diversity of insects and their behaviors. Some of the spring-to-midsummer bees, the Osmia mason bees, nest in tubular cavities. Typically these cavities are holes left behind by beetle larvae that matured inside a dead tree or stump before chewing their way out and flying away.

Mason bees move in after the beetles move out and create little mud-walled cells. In each cell they deposit a ball of pollen and a single egg, then repeat the process until the tube cavity is filled. So, to have mason bees to pollinate my delicious heirloom Northern Spy and Ashmead’s Kernel apples, I make sure our garden supplies nesting sites, mud, and plenty of pesticide-free pollen. We place sections of logs around the yard (obtained when neighborhood trees are cut or trimmed) to serve as beetle nurseries.

The adult beetles that emerge add color and character to the garden; the sight of a big, charismatic long-horned beetle is exquisite. Most insects in our yard, however, are tiny and easy to overlook. This includes a wide diversity of native bees. Little bees feed on little flowers, and one stalwart such flower in our yard is Erigeron karvinskianus.

Ceratina on Erigeron. Photo provided by Susan Masta

Mexican daisy is a filler plant, willing to jump in at a moment’s notice and claim any bare area of soil. Its tiny flowers are invariably full of tiny insects. I have netted four species of miniscule bees on a small patch of Erigeron flowers in a single sweep of the net. One of these bees is the abundant Ceratina acantha, which typically nest in pithy old stems. Protected inside, the larvae spend the winter eating pollen provisioned for them the previous summer. In spring, it is captivating to watch a little bee chew its way out of an old Salvia guaranitica stem, its tiny glistening eyes seeing the light of day for the first time. It is one of the surest signs that summer is on its way.

So be content and enjoy wandering through your winter and early-spring garden. Relax and don’t think about all the chores you “should” be doing. Leave a little mess, do a little less—and a whole miniature world of life will reward you for it!

Thank you, Susan, for sharing more about creating an insect-friendly garden!

HPSO members, you can visit Susan’s garden as part of the Open Gardens program. Please log in to the Member Center and search the Open Garden Directory for more details.

Susan’s garden will be open: 

  • June 4th, 2022, 10AM to 3PM
  • June 5th, 2022, 10Am to 3PM
  • Or by appointment

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