Some perennials can be used in place of shrubs

When planning a new mixed border, shrubs are often the first consideration. After shrubs are planted, perennials are chosen. Annuals are the finishing touch.

Sounds simple, right? Well, some plants defy categorization. They may appear to be shrubs, or are shrubs in warmer zones, but behave like perennials here. They die back to the ground each winter, with new growth emerging from the base in the spring. Or they may require special care to help them survive our tough winters.

Others are truly perennials, but have such a substantial, bushy form that they look like shrubs and, for the growing season at least, serve a similar function in the garden.

Amsonia

Amsonia should be in everyone's sun-filled garden. Growing up to 3 feet tall and wide, it boasts steel blue flowers in early summer. Amsonia is easy to grow, adaptable to many different soil types, and seldom needs dividing. Arkansas Amsonia has threadlike foliage; Willow Amsonia has attractive narrow leaves. Both put on a show in fall as their foliage turns brilliant golden yellow.

Baptisia

False indigo is a long-lived perennial that grows up to 3 or 4 feet tall and just as wide. In May and June, it bears showy, pea-like, blue flowers, followed later by black seedpods. Blooms are good for cutting, and the pods are outstanding in dried arrangements. The blue-green foliage grows in dense upright mounds. Although Baptisia is slow to mature, once established it is an ideal backdrop to smaller perennials.

False indigo is easy to grow, but difficult to move so plant them where they can stay. Site them in sun to part shade in well-drained soil.

Buddleia

In recent years hybridizers have taken notice of butterfly bushes introducing new colors and compact forms. A shrub in warmer places, it often dies back to the ground here. Numerous, long spikes of fragrant, tubular flowers are borne from midsummer until frost. They are butterfly magnets, and hummingbirds like them too.

They are available in almost every color in the rainbow, and range in height from dwarf, 3-foot varieties to larger plants up to 8 feet tall. Give them plenty of room in the garden. Their spreading branches grow outward as well as upward.

Butterfly bushes need special care to survive our winters. Plant them in a sunny location in rich soil with good drainage. Mulch plants over the winter, and cut them back to about 6 inches in the spring.

Caryopteris

For late summer blooms, consider planting Caryopteris. It dies down to the ground in our area. It bears attractive clusters of blue flowers in August over aromatic, toothed foliage. Growing 2 to 3 feet tall, Caryopteris combines beautifully with other late-bloomers like Autumn Joy Sedum. Give these plants full sun and good drainage, and cut them back hard to about 6 inches in late winter for the best blooms. Like Buddleia, they need a little help to make it through our harsh winters.

Persicaria

Commonly called giant fleeceflower, this bold perennial grows up to seven feet tall. It is a showstopper in midsummer when its large, white flower plumes appear. Grow giant fleeceflower in full sun to light shade in average garden soil. Allow enough space - it gets as wide as it does tall.

• Diana Stoll is a horticulturist and the garden center manager at The Planter's Palette, 28W571 Roosevelt Road, Winfield. Call (630) 293-1040, ext. 2, or visit planterspalette.com.