Gardening with Native Plants: Summer Sunflowers

Pale purple coneflower blooming on a slope

Pale purple coneflower (Echinacea pallida) blooming on a slope

July is our warmest month of the year, with still-long days and usually ample rain. Summer blooming plants reach full height and come into flower, and fall blooming plants continue vegetative growth. Our garden tasks are weeding, edging, and monitoring plants and pollinators.

In the prairie and savanna gardens, many species bloom in July, including diverse members of the sunflower family. Flowers in this family are clustered in compact heads—one must look closely to see the tiny individual flowers and their arrangement. Within a head (for example, a daisy or sunflower) there can be two types of flowers—disk flowers at the center and ray flowers surrounding the disk flowers. A head can also have only ray flowers (for example, dandelion) or only disk flowers (for example, blazing-star, Liatris spp.).

In this large family, species differ in habitat, mature height, floral form and color, and ability to spread by seed and/or rhizomes (underground stems). Many summer blooming members of the sunflower family are well suited to garden settings and others are weedy and may be managed before they spread or reproduce successfully.

In dry rocky or sandy soils, sand coreopsis (Coreopsis lanceolata) and prairie coreopsis (Coreopsis palmata) are easy to grow. The former has basal leaves with flower heads on taller stalks. It does well in open places where competition is minimal. The latter is about two-and-a-half feet tall and spreads by seed and rhizome. It is a slender plant and does not take over an area. Both of these species have yellow disk flowers and notched ray flowers.

Chicory (Chicorium intybus) is an introduced (non-native) plant with heads of pale blue ray flowers on slender branched stalks. A perennial with a strong taproot, it thrives on dry disturbed sites like roadsides but usually does not establish in the garden.

In mesic sites with full sun, ox-eye (Heliopsis helianthoides), wild quinine (Parthenium integrifolium) and pale purple coneflower (Echinacea pallida) continue blooming in early July. Ox-eye is three to four feet tall, with orange-yellow ray flowers and yellow disk flowers. Wild quinine has white disk and ray flowers in clustered heads. Only five of the ray flowers on each head are fertile; the disk flowers are sterile. Pale purple coneflower has drooping ray flowers and tiny fertile disk flowers forming a rounded center. Only a few disk flowers are in bloom at a time, blooming from the base of the cone up to the center. These three species spread by seed, not by rhizome.

In savanna gardens with light shade, flat-topped aster (Doellingeria umbellata) spreads by rhizome and seed. It blooms earlier than the other asters, with white ray flowers and yellow disk flowers clustered at the top of unbranched stems three feet tall. It can grow well in medium to moist soils.

In both prairie and savanna gardens, we manage weedy natives like horseweed (Conyza canadensis), a summer annual with tiny white ray flowers and yellow disk flowers, and Canada goldenrod (Solidago canadensis), a perennial native with extensive rhizomes and clustered yellow disk flowers only. During July we pull them before they bloom. Canada thistle (Cirsium arvense) is a persistent rhizomatous perennial with pink disk flowers only. It blooms in July and it is essential to treat or pull it repeatedly to prevent it from setting seed.

Especially this season, I’m inspired to hear from many gardeners asking plant ID questions, seeking gardening advice, and telling success stories from their gardens. Enjoy your summer observations and all you can learn about the diversity and beauty of native plants.

—Susan Carpenter, native plant gardener