Gardening with Native Plants: Midsummer

Tall sunflowers with yellow blooms in native plant garden

Compass plant blooming in the Native Plant Garden

Native plant gardens take on a summer look this month. Typically, July brings the warmest average temperatures of the year, peaking at an average high of 84 degrees late in the month. The number of species coming into bloom, especially in the prairie and savanna gardens, rises dramatically this month. With ample rain and warmer than average temperatures this year, some bloom times are earlier. Plants are taller and are bearing more flowers. Our garden tasks include weeding, planting, trimming along paths, and monitoring bumble bees.

Here are some July-blooming forbs that are beautiful and easy to grow. Most are relatively tall when in bloom, bearing flowers above basal leaves or leaves low on the stem. They are great garden accents because of their form, interesting foliage, and/or striking color.

Compass plant (Silphium laciniatum) and prairie dock (Silphium terebinthinaceum) have vertical, large, dissected or entire leaves, respectively. The bright yellow flowers are held on stalks up to nine feet tall. These plants should be transplanted when one or two years old, as they develop large storage roots after that time. The dry-mesic and mesic prairie gardens and Arboretum prairies are home to both species.

Late in the month, the bright pink blazing stars come into bloom, each suitable for different soil and moisture conditions. Cylindrical blazing star (Liatris cylindracea) grows up to two feet tall with flower heads borne on a loose spike. It grows best in full sun, in rocky soil. It grows in the Lime Prairie Garden near the Visitor Center and in upper Greene Prairie at the Arboretum.

Rough blazing star (Liatris aspera) grows up to three-and-a-half tall. The flower heads are round when in bud, with ten or more per spike. This species grows in dry to medium soils throughout the state. You will find it growing in the Dry Prairie Garden as well as in Arboretum prairies and on the West Knoll.

American lady butterfly on blazing star

Prairie blazing star (Liatris pycnostachya) has dense flower spikes, up to five feet tall. It thrives in full sun on medium to wet-mesic sites. Blooming begins at the top of the spike, with the youngest heads at the bottom. It grows in the Friends Terrace Garden with wild quinine (Parthenium integrifolium) and prairie dropseed (Sporobolus heterolepis). It also grows in Curtis, Greene, and Sinaiko Overlook prairies.

Culver’s root (Veronicastrum virginicum) may grow to five feet tall. It has whorled leaves on the stem, and small white flowers held on numerous narrow spikes. It thrives in full sun or light shade in medium soils. An important floral resource for the rusty-patched bumble bee, it also attracts other pollinators.

In July, cool season grasses like bottlebrush grass (Elymus hystrix), Canada rye (Elymus canadensis), and Junegrass (Koeleria macrantha) are producing seed, while warm season grasses like side oats grama (Bouteloua curtipendula), prairie dropseed, and big bluestem (Andropogon gerardii) are just coming into bloom.

Big bluestem in bloom

Several typical summer weeds usually appear in July: pigweeds (Amaranthus spp.), purslane (Portulaca oleracea), and crabgrass (Digitaria spp.). Thistles, burdock, and wild lettuce bloom, so remove them before their seeds scatter. Two native plants we try to weed from garden beds this month before they flower are giant ragweed (Ambrosia trifida) and common ragweed (Ambrosia artemisiifolia).

If you’re interested in bumble bee monitoring, please join us at the Arboretum on Sunday morning, August 11, for a workshop about bumble bee biology and identification, with an indoor presentation and time to observe and photograph bumble bees in the field. This workshop is free, but registration is required. For more details and to sign up, email Susan Carpenter by August 5.

With half the summer yet to come, enjoy July at the Arboretum and in your own garden.

—Susan Carpenter, native plant garden curator