10 Best Border Plants for Defining Your Garden

Angelonia with purple blooms in a garden — Credit:
Chayanan / Getty Images

Border plants offer definition along garden beds and driveways, creating neat lines that help to contain other vegetation. Of course, your exact selection will depend on your desired look. You could opt for flowery annuals for a more colorful scene or feathery evergreens for a more textural, elegant backdrop.

Here, we spoke to experts about the best border plants that will fit both of these briefs—and more. Read on to learn more about the best plants to help define and section off your garden.

Laura Janney, expert gardener and founder of The Inspired Garden
Sam Hoadley, manager of horticultural research at Mt. Cuba Center

01 of 10

Blazing Star

Blazing star (Liatris spicata) is a clump-forming perennial in the aster family "[It] lives up to its name, with showy spikes of tiny purple flowers that bloom in the summer," says Sam Hoadley, manager of horticultural research at Mt. Cuba Center.

This plant is native to the U.S. and attracts butterflies, bees, and other pollinators. "They look equally great in formal gardens or more naturalistic plantings," says Hoadley. As a bonus, they make wonderful cut flowers.

Zones: 3 to 8
Mature size: 3 feet tall x 1 to 2 feet wide
Care requirements: Full sun to part shade; moist soil

02 of 10

Beardtongue

With tall spikes of white, tubular flowers, beardtongue (Penstemon digitalis) is a natural fit for a border. Native to the U.S., beardtongue sends up blooms in late spring that can reach up to 3 feet tall.

"The flowers look great in the garden or in a cut flower arrangement, and they support pollinators," says Hoadley. As a bonus, these plants are generally deer resistant, which may keep these nuisances from crossing over the garden border.

Various cultivars with red or purple foliage are available for those who want a little extra flair, including Husker Red and Midnight Masquerade, says Hoadley.

Zones: 3 to 8
Mature size: 2 to 5 feet tall x 1 to 2 feet wide
Care requirements: Full sun to part shade; moist, well-drained soil

03 of 10

Butterfly Weed

Though "weed" is in its common name, this plant is anything but. Clusters of small orange flowers dot the top of this clumping perennial, which is tolerant of hot, dry, sunny conditions.

"Butterfly weed (Asclepias tuberosa) supports monarch butterflies, whose caterpillars are only able to eat different types of milkweed plants," says Hoadley. Its blooms proliferate from June to August, so you can enjoy them along a garden border all summer long.

Zones: 3 to 9
Mature size: 24 inches tall x 18 inches wide
Care requirements: Full sun; dry, rocky soil

04 of 10

Catmint

Catmint (Nepeta racemosa) is an aromatic perennial with a clumping habit. It is easy-going and can tolerate a range of conditions, including poor soil and drought.

"It has light, dusty-green foliage with soft spikes filled with tiny purple blooms," says Laura Janney, founder of The Inspired Garden. "I prefer using shorter varieties for garden borders, as they add beautiful texture."

Zones: 4 to 8
Mature size: 24 inches tall x 30 inches wide
Care requirements: Full sun; dry soil

05 of 10

Veronica

Veronica, also known as speedwell, blooms all summer with long, dense spikes of star-shaped flowers. Depending on the species, its colors range from icy blue and light purple to white.

"Veronica's striking texture complements most perennials," says Janney. "Its blooms resemble paintbrushes in the garden!" With regular deadheading, this perennial will continue blooming throughout the summer until the first frost.

Zones: 4 to 8
Mature size: 2 feet tall x 1 foot wide
Care requirements: Full sun to part shade; well-drained soil, medium watering

06 of 10

Salvia

Salvia is a member of the mint family with aromatic leaves. Its flowers can be vibrant blue or pink.

"It's hardy and reliable, bringing color when most other perennials haven't yet emerged," says Janney. "I love how its spiky flowers contrast with rounder foliage, creating a dynamic, visual effect." Cut it back to encourage a second bloom later in the summer.

Zones: 5 to 10
Mature size: 18 inches tall x 1 foot wide
Care requirements: Full sun; well-drained soil

07 of 10

Periwinkle

Periwinkle (vinca) is a good choice for gardens that have full sun. These flowers come in a range of colors, from purples and blues to magentas, pinks, and whites.

"Its compact growth makes it ideal for filling gaps in a garden border," says Janney. They also bloom reliably into the fall, giving your garden some extra color once many others have fallen away.

Zones: 4 to 8
Mature size: 4 to 6 inches tall x 6 to 18 inches wide
Care requirements: Full sun; rocky, well-drained, dry soil

08 of 10

Aromatic Aster

Contrary to its name, aromatic aster (Symphyotrichum oblongifolium) flowers have no scent, although their crushed leaves have a balsam-like smell.

"Cultivars of the species, like October Skies and the new Twilight Sky are easy to care for, adaptable plants that are drought-tolerant and deer-resistant," says Janney.

Aromatic aster blooms in late fall through November with purple, daisy-like flowers. They'll also help feed pollinators later in the season.

Zones: 3 to 8
Mature size: 1 to 3 feet tall x 1 to 3 feet wide
Care requirements: Full sun; dry soil

09 of 10

Floss Flower

Floss flower (Ageratum houstonianum) has beautiful, fragrant blue flowers that can cover the entire plant.

"Its fuzzy, button-like blooms add a subtle sparkle to garden borders," says Janney. Though typically an annual, it will liberally reseed itself and return again the following year.

Zones: 2 to 11
Mature size: 6 to 30 inches tall x 6 to 18 inches wide
Care requirements: Full sun to part shade; rich soil, medium watering

10 of 10

Angelonia

Angelonia is an annual with dainty flowers that resemble snapdragons. "It's a tough, heat- and humidity-tolerant annual that brings an English cottage garden charm," says Janney.

Cultivars of angelonia come in white, light blue, pink, and magenta colors, creating a rainbow of blooms along a garden's edge.