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To Attract Insects, Grow Native Plants
by Erika Jensen - July 2013

Just like everyone else, I sometimes have moments of loathing for insects. It’s amazing the bugs that will practically walk through your walls if you live in an over 100-year-old farmhouse like I do. Box elder beetles, Asian lady beetles, house spiders and cluster flies – these are some of the bugs I love to vacuum. Yet, I recognize that insects also have a very important role to play in nature, whether as predators or parasitoids of pest insects, or even as food for other animals.

“Attracting insect life is a hard sell for many people,” said Bill Carter, co-owner and president of Prairie Moon Nursery in Winona, Minn. “They just don’t care about all those bugs. But I tell them that if you like birds, you need to have bugs, since 96 percent of all birds need insects as part of their diets at some point in their lives – even hummingbirds.”

According to Carter, hummingbirds feed their young a certain kind of native bee, and that bee feeds on a native plant: New Jersey tea (Ceanothus americanus). It’s a 3-foot tall shrub with white flowers that bloom from June through August.

Food and Nursery


Bees and other pollinating insects gather nectar and pollen from swamp or rose milkweed (Asclepias incarnata). 1

Monarch caterpillars feed on a variety of native milkweeds, such as this swamp or rose milkweed (Asclepias incarnata). 2

Many insects use plants not only for a source of nectar, but also as a nursery for their young. By now, many people are familiar with the life cycle of the monarch butterfly (Danaus plexipus). Monarchs summer in places like the Upper Midwest where they raise their young, then vacation in Mexico during the winter. Although the adult butterflies drink nectar from many kinds of flowers, they will only lay their eggs on one kind of plant – milkweed. According to the U.S. Forest Service, over 100 species of milkweed (Asclepias spp.) exist in North America, but only about one-fourth of them are known to be important host plants for monarch butterflies. Without milkweed, monarchs are unable to reproduce.

“I’m concerned about the decline in the milkweed population around here,” Carter said. “With so many farmers growing Roundup-ready crops, there’s no milkweed growing in fields like there used to be. Fortunately, many CRP (Conservation Reserve Program) plantings now include milkweed, and it’s included as a part of many roadside plantings as well. At Prairie Moon, we’ve been giving away free seed packets to customers to get more milkweed out there.”

The federally endangered karner blue butterfly (Lycaeides melissa samuelis) is another example of an insect that needs a native plant as a host for its young. These butterflies lay their eggs on native wild lupine (Lupinus perennis). Lupine will only grow in well-drained, sandy soil, which means its habitat is restricted to certain areas. The butterfly is most widespread in Wisconsin, and can be found in portions of Indiana, Michigan, Minnesota, New Hampshire, New York and Ohio. It may also be present in Illinois.

Species or Cultivars?

“Planting a hybrid lupine, such as Russell hybrids, doesn’t work,” Carter said. “It has to be the native kind. In some circumstances, the hybrids crossed with native lupine and became unattractive to the butterflies.”


The blue karner butterfly is hardwired to lay eggs on the native lupine (Lupinus perennis), which serves as a food source for the caterpillars as they emerge. 3

For gardeners who want to know more about native plants and how they are connected to native wildlife, Carter recommended Bringing Nature Home: How You Can Sustain Wildlife with Native Plants, a book by Douglas W. Tallamy. The Xerces Society (xerces.org) also has a number of useful references.

Another part of the story is the role of insects in controlling other insects. I discovered early on as a vegetable farmer that pest insect populations can very quickly get out of control. But if you have a diversity of insects, and more specifically insect predators, you can win the war before you have to fight a single battle. Insect predators typically eat many prey during at least one stage in their life cycle. Many gardeners are already familiar with lady beetles. In their larval as well as adult forms they can eat hundreds of aphids, and sometimes mites and scale insects. Adults feed on pollen and nectar, so it’s important to have flowers present.

Killer Bugs

Parasitoids are insects that lay their eggs on other insects, which then serve as food for the developing young. They are most often wasps, such as the non-stinging braconid wasp. These parasitize the larvae of lepidopterans, such as sphinx moths, cabbage butterflies and gypsy moths. Plants in the Apiaceae family, such as golden Alexanders (Zizia aurea), cow parsnip (Heracleum maximum) and angelica (Angelica atropurpurea) are the best for attracting this insect.

One fantastic resource I found when getting started was Attracting Beneficial Insects with Native Flowering Plants, a bulletin published by the Michigan State University Extension, and available free for download at http://nativeplants.msu.edu/uploads/files/E2973.pdf.

This handy resource has a list of native plants that have been found to attract a greatest diversity of insects and bees.


New Jersey tea (Ceanothus americanus) is a 3-foot tall shrub that blooms most of the summer to attract bees and other beneficial insects. 4

Golden Alexanders (Zizia aurea) support nonstinging braconid wasps and other parasitic insects. 4

Diverse Plantings are Key

In 2007, I planted three vegetable garden beds in a mix of natives, including golden alexanders (Zizia aurea), rose or swamp milkweed (Asclepias incarnata), yellow coneflower (Ratibida pinnata), nodding wild onion (Allium cernuum), great blue lobelia (Lobelia siphilitica), Riddell’s goldenrod (Solidago riddellii) and smooth aster (Aster laevis, syn. Symphyotrichum laeve var. laeve). My experience was very positive. The diversity of insects attracted by the mix of plants really seemed to help control pests. For example, I used to spray several times a season for Colorado potato beetles. Now I usually only spray once or twice a year – sometimes never.

I also found that many of the natives have good potential as garden plants. In particular, I really liked nodding wild onion and great blue lobelia. I noticed that the natives mostly took care of themselves and didn’t need the extra TLC that annual flowers require. Native plants often have deep root systems and are drought tolerant after establishment.

There are lots of different reasons to grow native plants, but the best selling point for me is that they support other parts of the ecosystem, such as insects, birds and other wildlife. Planting natives is my way of promoting diversity in my own small corner of the universe.

PHOTO CREDITS:

1. Photo courtesy of U.S. Department of Agriculture
2. Photo courtesy of iStockphoto.com
3. Photo courtesy of Charles and Diane Peirce/Michigan Wildflowers.
4. Photo courtesy of wildflower.org

 


Erika Jensen is a vegetable farmer living in Waupun, Wis. She is the past executive director of the Gottfried Prairie and Arboretum, a native plants arboretum and prairie restoration.

 

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