The Iowa Gardener: Plant with monarchs in mind

The beloved monarch butterfly needs our help.

Earlier this summer, it was officially designated as endangered by the International Union for Conservation of Nature. Scientists estimate that the monarch population has dropped at least 20 percent and as much as 90 percent over the last several decades.

There are multiple culprits. The monarchs that spend their summers in Iowa also overwinter in central Mexico, where deforestation has reduced their habitat. The continual use of pesticides in the United States and Canada also has diminished their numbers.

Here in the Midwest, there have been dramatic drops in strategic locations of milkweed, where adult monarchs lay eggs so developing larvae can feed on it. (Monarch larvae cannot grow on any other plant other than milkweed.)

It used to be that many Iowa agricultural fields were filled with milkweed, nicely spread out. The milkweed stands were scattered enough that predatory insects had a hard time finding the monarchs in among the crops. But Roundup Ready crops — crops that have been bred for resistance to the non-selective herbicide, which otherwise kills any other plants it touches—over the past 20 years have allowed farmers to grow crops that are nearly weed-free. The result is that an important habitat for the monarch population has all but disappeared.

In fact, Campbell Watts, co-founder of the Monarch Research Project in Marion, said that milkweed in fields was at one time home for probably at least a third of monarch larvae in Iowa.

What can the gardener do to help? Watts and Rick Hellmich, a retired entomologist with the USDA Ag Research Service in Ames, recommend the following.

Plant milkweed to host monarch larvae. Two types that are especially valuable for Iowa monarchs are common milkweed (Asclepias syriaca) and swamp milkweed (Asclepias incarnata). Other good types for Iowa are butterfly weed (Asclepias tuberosa), whorled milkweed (Asclepias verticillata), and poke milkweed (Asclepias exaltata).
Plant flowering nectar plants for adult monarchs. Meadow blazing star (Liatris ligulistylis), for example, is a monarch magnet in the summer and New England aster (Symphyotrichum novae-angliae) is an excellent fall source. However, there are many other flowering garden annuals and perennials that monarchs love. (See accompanying list.)
Plant native plants. Monarchs also will feed on hybridized and non-native plants, but native flowering plants have co-evolved with native butterflies and bees and tend to be the best food sources.
Cultivate a landscape that has flowers from May through October. Most perennials and annuals are in flower in Iowa gardens for only a few to several weeks at a time, so plant a variety to provide a nectar source of one type or another for months, right up until the monarchs migrate south in fall.
Don’t use pesticides. They are designed to kill harmful insects but also kill many beloved and beneficial insects, including monarchs (not to mention bees and other butterflies). This includes sprays, granules, and powders that you personally might apply, or anything a lawn or garden service might apply for insects such as grubs.
Provide a water source. A bird bath or fountain attracts butterflies, alighting for a sip. The same is true for water gardens.
Welcome sun. Butterflies like to hang out in sunny spots, so the more sun your landscape has, they more they will thrive in it.

How much of a difference can gardeners make? Watts says home landscapes in Iowa are a small part of the equation, but planting with monarchs in mind is a wonderful way to do your part. It also helps educate and inspire others, everyone from your children to the neighbors walking by and enjoying all those butterflies.

For more information, visit the Monarch Research Project website at https://monarchresearch.org/.

Veronica Lorson Fowler is co-publisher of the Iowa Gardener website at www.theiowagardener.com.

Good Iowa Nectar Plants for Monarchs

Planting these flowers can help monarchs and other pollinators.

Early-Summer Flowering

Culver’s root (Veronicastrum virginicum)

Hoary verbena (Verbena stricta)*

Stiff tickseed (Coreopsis palmata)

Mid- and Late- Summer Flowering

Black-eyed Susan (Rudbeckia hirta)

Eastern purple coneflower (Echinacea purpurea)

Maximilian sunflower (Heliantus maximiliani)

Meadow blazing star (Liatris ligulistylis)*

Ontario blazing star (Liatris cylindracea)

Prairie blazing star (Liatris pycnostachya)

Wild bee balm (Monarda fistulosa)

Autumn Flowering

Leadplant (Amorpha canescenes)

New England aster (Symphyotrichum novae-angliae) *

Sawtooth sunflower (Helianthus grosseserratus)

Stiff goldenrod (Oligoneuron rigidum var. rigidum)

Tall blazing star (Liatris aspera)*

Tall boneset (Eupatorium altissimum)

*Especially good monarch attractant

For more information, visit www.xerces.org or monarchresearch.org

Source: Xerces Society for Invertebrate Conservation.

A monarch butterfly lands on some swamp milkweed in an area of natural prairie at Noelridge Park in Cedar Rapids on Aug. 12, 2011. Planting milkweed is important for monarchs because larvae cannot grow on any other plant other than milkweed. (The Gazette)

A monarch caterpillar devours a milkweed leaf in Cedar Rapids July 21, 2010. Monarchs spend two weeks of their lives as caterpillars, eating milkweed non-stop the whole time. (The Gazette)

A monarch butterfly rests on a flower in the Butterfly House during the Johnson County Fair July 24, 2013, in Iowa City. Gardeners can help the plight of the monarch by planting milkweed and other nectar producing plants that they like, including blazing star, bee balm, verbena and butterfly weed. (The Gazette)