Little Lanterns and Pink Lanterns are shorter varieties of columbine.
Bluestar (Amsonia). "I've never met an amsonia I didn't like," Cohen said. These sun lovers play two roles in the garden: They produce sky blue flowers in spring, and then their foliage remains attractive all summer and turns yellow in fall. One new variety she especially likes is Blue Ice.
Fringed bleeding heart (Dicentra eximia). The more familiar form of bleeding heart is a spring favorite of many gardeners, but once it's done blooming, that's it. Fringed bleeding heart, on the other hand, will rebloom if it's deadheaded, Cohen said. She often gets a good flowering in fall.
Jacob Cline, Raspberry Wine or Pink Lace bee balm (Monarda didyma'Jacob Cline,' 'Raspberry Wine' or 'Pink Lace'). Gardeners love bee balm both for its appearance and its ability to attract bees, butterflies and hummingbirds, but the plant is susceptible to powdery mildew. The varieties she recommends are resistant to the disease, which creates an unattractive powdery coating and can cause leaves to drop.
Jeana garden phlox (Phlox paniculata'Jeana'). Like bee balm, garden phlox often suffers from mildew, but Cohen said she's never had the disease on the variety Jeana. Its individual flowers are very small, but they grow in big, showy clusters.
Agastache. This plant is a magnet for butterflies and hummingbirds. It can be an aggressive grower, but if deadheaded, it will flower from early summer right on till fall. "What more do you want from a perennial?" Cohen asked.
Prairie Glow brown-eyed Susan (Rudbeckia triloba'Prairie Glow'). This newer variety has gorgeous flowers with burgundy, bronze and reddish-orange tones, which is probably why the plant is hard to find. Cohen has two words for her reaction to it: "plant lust."
Cranberry Crush hardy hibiscus (Hibiscus moscheutos'Cranberry Crush'). This variety produces big, cranberry-colored blooms from summer to fall. If you grow it, though, be prepared to do battle with Japanese beetles.
"Do not plant these next to your roses," Cohen advised. "You'll commit suicide."
Fireworks or Solar Cascade goldenrod (Solidago rugosa'Fireworks' or S. shortii'Solar Cascade'). Goldenrod brings fall color to the garden, but it's gotten a bad rap, and unfairly so. Many people think goldenrod triggers hay fever, but in fact its pollen is too heavy to be carried by the wind from the plant to your nose. It's ragweed that makes you sneeze, not goldenrod.
Cohen likes Fireworks for its arching habit and Solar Cascade for its smaller size.