Gardening with Native Plants: Summer Begins

White wild indigo

White wild indigo

As June 2019 begins, cool wet spring conditions continue. June is Madison’s rainiest month; the long-term average monthly precipitation is 4.5 inches. The State Climatology Office cumulative precipitation graph shows above average snow and rainfall since the beginning of the “water year,” October 1, 2018. New and returning volunteers and students are working in the garden, weather permitting. Our tasks include: planting, weeding, edging, learning to recognize seedling and vegetative stages of native plants and weeds, and monitoring plants and animals, including pollinators.

In May, we saw migrant insects arrive in the garden—green darner dragonflies (Anax junius) and monarch butterflies (Danaus plexippus). This month, on abundant milkweed, look for monarch eggs and tiny larvae. We are planting more milkweeds in the garden, including prairie milkweed, Asclepias sullivantii. It is similar to common milkweed in height but has fewer flower clusters. The leaves are glabrous (hairless) on the underside and the leaf midribs may be pink or red. It grows best in full sun, in mesic or moist loamy soils. It can spread by rhizome (underground stems), although not as aggressively as common milkweed. It blooms in June and July, is pollinated mainly by large bees like bumble bees, and produces large pods of windblown seeds. You may want to protect new plantings from rabbits, who seem to prefer this species to other milkweeds.

Rusty-patched bumble bee queen foraging on native honeysuckle
Rusty-patched bumble bee (Bombus affinis) queen foraging on native honeysuckle, June 6, 2018

We continue to monitor bumble bees at the Arboretum. During the cool and rainy delayed spring, we have seen spring queens of several species: two-spotted (Bombus bimaculatus), common eastern (B. impatiens) and black and gold (B. auricomus) at the Arboretum, as well as half-black (B. vagans), brown-belted (B. griseocollis), red-belted (B. rufocinctus), yellow (B. fervidus), and rusty patched (B. affinis) bumble bees in the region. So far, we are observing fewer spring queens than usual, perhaps because of wet conditions as they attempt to establish nests and rear the first set of workers for each colony.

The Wisconsin Department of Natural Resources Bumble Bee Brigade bumble bee monitoring project is in its second year, offering trainings, resources, and new mapping and data features for statewide participants. You can contribute valuable data from your own garden and/or from places you visit throughout the state.

Early summer is a good time to begin monitoring bumble bees, as the queens are large and easily seen and heard as they nectar and gather pollen to provision their nests. When the workers emerge from the colony to forage, more bees will be in the garden and you will have more chances to observe and photograph them. You will find them foraging in the native plant garden on spiderwort (Tradescantia ohiensis), wild indigos (Baptisia spp.), wild roses (Rosa spp.), beardtongue (Penstemon spp.), and wild lupine (Lupinus perennis), and in Longenecker Horticultural Gardens on azaleas, horse chestnuts (Aesculus spp.), and other flowering ornamental plants.

The Arboretum will offer a bumble bee ID workshop on June 23, 9 a.m.­–12 p.m., including life history, ecology, identification, and time in the field. For more details, or to sign up for this workshop, please contact Susan Carpenter.

As summer begins, add native plants to your garden, learn about pollinators in Wisconsin, photograph insects you find, share your bumble bee sightings with others (at Bumble Bee Brigade), or join a garden tour.

—Susan Carpenter, native plant gardener