Our native gardens take on a summer look this month. July brings the warmest average temperatures of the year, with a peak 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. Garden tasks include weeding, edging, trimming along paths, and harvesting seeds from plants that bloomed four to six weeks ago.
These July-blooming forbs are beautiful, easy to grow, and attractive to bumble bees and other pollinators. Many bear flowers above basal leaves or leaves low on the stem. They are great garden accents because of their form, interesting foliage, and 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 tall stalks up to nine feet tall. These plants should be transplanted when only 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.
This month, the bright pink blazing-stars come into bloom, each suitable for different soil and moisture conditions. Cylindrical blazing star (Liatris cylindracea) is the smallest, up to 24 inches tall with flower heads in a loose spike. It grows best in full sun, in rocky soil. It grows in the lime prairie garden and in upper Greene Prairie at the Arboretum.
Rough blazing-star (Liatris aspera) grows up to 40 inches tall. The flower heads are round when in bud, with 10 or more per spike. This species grows in dry to medium soils in a wide geographic range in Wisconsin. You will find it growing in the new dry prairie garden.
Prairie blazing-star (Liatris pycnostachya) grows up to 60 inches tall, with dense spikes. It thrives in full sun, on medium to wet-mesic soils. Blooming begins at the top of the spike, with the youngest heads at the bottom. It is growing at the Friends Terrace circle garden, grouped with wild quinine (Parthenium integrifolium) and prairie dropseed (Sporobolus heterolepis). It also grows in Curtis, Greene and Sinaiko Overlook prairies.
Meadow blazing-star (Liatris ligulistylis) grows 24 to 36 inches tall, with rounded flower heads along the vertical main stem. Each flower head has its own small stalk. This plant grows well in mesic soils in full sun, although it can tolerate drier conditions on sandy and rocky soils. It is visited by bees, hummingbirds, hummingbird moths, and butterflies, especially monarchs.
Cool season grasses like bottlebrush grass (Elymus hystrix), Canada rye (Elymus canadensis) and June grass (Koeleria macrantha) produce seed this month, while warm season grasses like side-oats grama (Bouteloua curtipendula), prairie dropseed, and big bluestem (Andropogon gerardii) begin blooming.
Summer weeds usually appear this month: pigweeds (Amaranthus sp.), purslane (Portulaca oleracea), and crabgrass (Digitaria sp.). Non-native thistles and burdock bloom, so remove them before seeds scatter. Two native plants to weed out this month before they flower are the giant ragweed (Ambrosia trifida) and common ragweed (Ambrosia artemisiifolia).
Enjoy your garden in the second half of the summer.
—Susan Carpenter, native plant garden curator