To many people, the term "wildflower garden" conjures up images of a collection of delicate spring wildflowers native to lightly shaded woodland sites or moist meadows. However, there are numerous summer-flowering wildflowers native to dry, sunny hillsides, glades, and other areas with more austere conditions for plant growth. Many of them are much easier to grow than spring wildflowers and may be ideal candidates for adding color to a low-maintenance, summer flower garden.
First, it must be emphasized that wildflowers should not be dug from the wild. Harvesting plants from the wild is a destructive act that can damage the ecosystem along with the plants and animals that call it home. To discourage this practice, Missouri has state statutes pertaining to the removal of plants from state and county highway and roadway right-of-ways. In general, these statutes make it illegal to "dig or remove any plants or plant parts" from those right-of-ways without permission. However, they do allow "the collection of seeds, fruits, nuts, berries, edible wild greens or flowering parts of plants" for personal use.
One of the favorite and most colorful of the summer wildflowers is butterfly weed (Asclepias tuberosa). It often is found growing in poor soil along roadsides. Although it does attract butterflies, it probably is not fair to call it a "weed." In summer, it produces clusters of small, bright orange flowers that are strikingly attractive.
Butterfly weed is a member of the milkweed family and produces pointed seed pods containing fluffy seeds that are distributed by the wind. Easily grown from seeds, it forms dense, colorful clumps. The flowers are useful for cutting and displaying in arrangements. As an added incentive to include them in a garden, members of the genus Asclepias serve as the sole source of food for monarch butterfly larvae. Therefore, growing this species is a good way to help in the monarch butterfly preservation effort.
Another plant that can be found along Missouri roadsides is black-eyed Susan (Rudbeckia hirta). Both drought and heat tolerant, it produces abundant amounts of daisy-like flowers with golden petals and dark centers beginning in early summer. Plants often continue to flower periodically until October. Black-eyed Susan also provides desirable, long-lived cut flowers to use indoors in flower arrangements and is attractive to pollinators.
Purple coneflower (Echinacea purpurea) is another species of wildflower that adds color to the summer landscape. It produces daisy-like flowers with purplish-pink petals and dark, reddish-brown centers. A common inhabitant of roadsides and prairies, it is easy to start from seeds. The latter can be direct-seeded any time in late summer. Alternatively, seeds can be planted in coldframes in late winter/early spring and transplanted to the garden when the young plants are large enough to handle. Purple coneflower also is very pollinator friendly.
For the gardener who wants extended bloom time from a single native plant, rose verbena (Glandularia canadensis) is a good candidate. This low, sprawling plant bears small lavender or magenta flowers in clusters. Unlike the leaves of garden verbena (Verbena x hybrida), rose verbena has leaves that are deeply lobed. It makes an excellent rock garden plant and, in sunny locations, may flower from spring until a late fall freeze occurs.
In locations having light shade and fairly moist soil, several other summer-blooming wildflowers may be used. One of the best is campanula, or tall bellflower (Campanula americana). It, too, flowers throughout most of the summer and produces blue flowers on a tall spike. In spite of its name, flowers of this species are not bell-shaped, but take on the appearance of a five-pointed star. In ideal conditions, flower stalks of tall bellflower may achieve a mature height up to six feet.
Another plant related to tall bellflower and that grows in similar locations is blue lobelia (Lobelia siphilitica). Also known as blue cardinal flower, it flowers in late summer producing flowers that range from light to dark blue in color. Blue lobelia is a fairly small plant that normally grows no more than three feet in height.
For vivid red flowers, cardinal flower or cardinal lobelia (Lobelia cardinalis) is spectacular. In addition to being an extremely hardy native wildflower, it is famous for attracting hummingbirds and swallowtail butterflies. Like blue lobelia, it prefers low, moist areas and light shade. It, too, is a member of the bellflower family.
There are many other prairie and woodland summer-flowering native perennials that may be used in the garden. Aromatic aster (Symphyotrichum oblongifolium) and goldenrod (Solidago spp.) are two such examples. Both were taken to England many years ago, where improved types were developed for garden planting.
Additional wildflowers worthy of consideration for garden use include gayfeather or blazing star (Liatris spicata), evening primrose (Oenothera biennis), penstemon or beardtongue (Penstemon spp.), and perennial sweet pea (Lathyrus latifolius).
For additional information, see MU Extension publication G6660 titled Wildflowers in the Home Landscape. This publication can be found at https://extension.missouri.edu/publications/g6660.