Insect superfoods

Visiting Coastal Maine Botanical Gardens this week brought some encouraging news about insect-friendly plantings. The designers had showcased many of the same flowers I’m growing to attract insect visitors, some inside the butterfly house near the entrance to the garden. Monarchs fluttered around this enclosed space, lighting on swamp milkweed and purple coneflowers. I spotted two species of caterpillars on stalks.

Monarch on purple coneflower in the butterfly house

   
    Planting for insects isn’t just for pollinators. It’s also intended to help leaf-eating insects, particularly caterpillars of moths and butterflies. 

Monarch caterpillar

Therefore Thomas Berger performed a useful service by cross-referencing lists of the best plants for these two purposes to derive a master list of insect “superfoods” posted by the Ecological Landscape Alliance. At the top of the section on herbaceous plants were goldenrods, asters, and sunflowers.

    Goldenrods support 11 species of specialist bees—bees that can only feed on a limited group of native flowers—and 115 kinds of lepidopteran caterpillars (caterpillars of butterflies and moths). Asters and sunflowers aren’t far behind. Goldenrods attract monarch butterflies and feed their caterpillars, making them second to milkweeds for supporting these fast-disappearing butterflies. 

    This is good news for my garden, because lots of goldenrods and asters are growing here already. I started some goldenrod from seed years ago. Patches of goldenrod here and there mark its spread around the yard. Unfortunately I didn’t keep a record of which species I’d planted. From photos, I suspect it was blue-stemmed goldenrod, Solidago caesia. Two years ago I bought some sweet goldenrod, Solidago odora, for a new perennial bed. Both native species have proven to be easy to grow and free-flowering.

    Goldenrods are members of the Compositae, also called Asteraceae, a useful family of plants because their central discs are made up many tiny flowers, each with pollen to offer. 

Visiting a daisy flower is an efficient way to collect pollen

The “petals” of the daisy-shaped blooms are actually strap-shaped flowers too. So an insect visiting one of these composite flowers gets lots of pollen with minimal travel. Goldenrod blooms are small, but if you look closely, you’ll see they share the family shape. 

Goldenrod's tiny daisy flowers

 

By the way, goldenrod doesn’t trigger hay fever. It has sticky pollen that doesn’t blow around like that of real culprits, such as ragweed.

    I’m growing some New England asters (Symphyotrichum novae-angliae) with pretty blue flowers. But aster volunteers are much more plentiful in the garden. In the past few years, a white-flowered type has popped up in lots of part-shaded spots with no effort on my part. I suspect it’s white wood aster, Eurybia divaricata.

Aster volunteers

    Last week I wrote about my bad luck growing sunflowers. I learned from Berger’s post that Helianthus annuus, the garden or field sunflower, was brought to New England by Native Americans as an agricultural crop and isn’t native here, although our local specialist bees can still use it. A native option is woodland sunflower, Helianthus divaricatus. Meanwhile, I’m growing oxeye sunflower, Heliopsis helianthoides, also called false sunflower, a different native genus but useful to pollinators too.

Oxeye sunflower

 

Attracting native insects

I just got back from Oregon, where shade plants that are expensive and finicky in the Northeast grow as wildflowers on the forest floor.

Trillium everywhere

It must be fun to garden in that ecosystem. Arriving home, I was eager to see how my new perennial bed was faring after a dry July week. 

    So far so good. The yarrow flowers (Achillea ‘Coronation Gold’) are still yellow, just starting to turn brown as seeds form. St. John’s wort’s (Hypericum ‘Universe’) sunny blooms have given way to handsome fruits that will persist into winter.

Yarrow flowers have lasted a month

     Balloon flower (Platycodon grandiflorus) is blooming now. Most of mine are blue, but one mislabeled white-flowered specimen came home with me, and I moved it into the new bed, where it’s settling in happily. 

White balloon flowers

Goldenrod (Solidago odora) and dwarf goat’s beard (Aruncus aethusifolius) are getting ready to flower. The grasses and clumps of iris are expanding, filling in some of the blank spaces.

    Back next to the vegetable bed, plants I chose to benefit native insects are going strong. Swamp milkweed (Asclepias incarnata), purple coneflower (Echinacea purpurea), white-flowered Phlox 'David', and black-eyed Susan (Rudbeckia hirta) are blooming generously. Dusty pink Sedum ‘Autumn Joy’ will open next.

Insectary bed blooms

    As I’d hoped, the flowers are attracting lots of pollinators. Bees are flying from blossom to blossom. We spotted a hummingbird last week, and monarch butterflies have visited on their way through town.

A monarch touches down

    Beneficial insects are gathering too. A dragonfly staked out a perch on top of a tuteur supporting cucumber vines. Presumably a high perch allows insect predators to scan for their prey, like raptors on high dead tree branches. With plants attracting a broad array of native insects, I shouldn’t have to buy beneficial insects such as ladybugs and parasitic wasps. They’ll be drawn to my yard if I offer them enough of the right prey.

    Leaf-eating insects are here too. They’re a little harder to feel good about, because they chew holes in leaves, but they’re important at the base of the food web. I notice that the foliage of the goldenrods I planted in the new bed is getting frayed. That’s good, because this genus supports 115 species of butterflies and moths by providing leaves for their larvae to eat. 

Goldenrod foliage and flowers provide for native insects

With a few goldenrods in the bed, the damage is spread around, and it doesn’t bother me. If I’m lucky, those monarchs may have laid some eggs on the three kinds of milkweed I’m growing so that their caterpillars can eat the leaves.

    Seeing insects and birds in the garden means I’ve got enough flowers blooming and enough of the vegetation they like to eat to make it worthwhile for these creatures to spend time in my yard. That was my hope when I chose the plants for the new bed and when I designed the insectary bed next to the vegetable growing area. I’ve come to believe that to be sustainable, a garden has to provide food and habitat for native insects.

Native plants for native insects

Wake up and smell the leaf mulch

Last fall I changed a longstanding fall garden clean-up routine: I didn’t rake fallen leaves from the garden beds and chop them up in the leaf shredder. I didn’t mulch those same beds with the chopped leaves. I didn’t cut the dead perennials’ foliage and flower stalks to the ground. I just let the tree leaves lie on top of the plants and left the dead stalks standing.

Meadow rue (Thalictrum aquilegiifolium) emerging through the leaf litter

    My reason for this change of approach was that I’d learned that native insects shelter and lay eggs under fallen leaves, in crowns of dormant perennials, and in those dead flower stalks. If I left those insects alone through the winter, they’d have a better chance of surviving, reproducing, and contributing to the garden ecosystem in spring. It was hard to hold myself back from cleaning up at the end of the garden season. I have to admit it was also a lot less work.

Beneficial lacewing finding winter cover

    Through the winter, I watched those ragged stalks and those whole leaves, especially on the new perennial bed that’s right next to the back deck. The leaves are mostly red oak, with some Norway maple mixed in. The garden’s usual winter look, bare but neatly tended, had morphed into either a sloppy mess or a more natural scene, depending how I felt on a given day. 

The backyard scene in March

Now is the time to assess how this lazy approach to preparing for winter worked out.

    I waited impatiently for daytime temperatures to stay in the fifties, indicating that the time had come for lifting the leaves off the new plants and moving them to the compost pile. I was anxious to know how the plants were doing under there. For the past two weeks I’ve been gradually uncovering the deck bed. 

Perennials and a dwarf juniper under the leaves

Dry leaves formed the top layer, but beneath these I uncovered wet, matted leaves plastered to the ground. I chose overcast days with rain in the forecast, not hard to find recently, for exposing the covered plants to the light. Their new foliage was pale from growing in the dark. I didn’t want them to get sunburned from sudden exposure to full sun.

    With the whole bed uncovered, I see that most of the new perennials made it through the winter. Of course, they benefited from other factors besides the leaf cover. Snow covered the bed during much of the winter, protecting the new plants from desiccation and temperature extremes, and there’s been plenty of rain this spring.

    To mulch the uncovered bed, I shredded leaves that I’d stored in the garage in paper yard waste bags. 

Shredding makes mulch that doesn't mat or blow around like the whole leaves

If insects took refuge in the bags last fall, they should have moved out by now. Birds are very active in the yard, which seems like an indication that they’re finding insects to eat. 

A cardinal couple is building a nest

     I’m hoping that more native insects will enrich the garden’s food web this year. Not only animals will benefit. I’m aiming for plant-friendly balanced populations of pollinators, leaf-eaters, and the beneficial insect predators that will keep leaf-eaters under control.

Leaf litter and native insects make congenial conditions for woodland plants