Biennials: Garden Plants on the Move

by Kathryn Ptacek

Hollyhocks ... forget-me-nots ... foxglove ... Sweet William ... these names conjure up the somewhat staid — and static — vision of Grandma's old-fashioned cottage garden, and yet, according to Richard Kaweske, owner of Fair Acres Farm in Sussex, New Jersey, biennials are plants that take a walk on the wild side.

"Perennials don't move and annuals can't self-seed, but biennials self-seed, and they move." Some seed, Kaweske says, falls to the ground close to the original plant, while others will cross a sidewalk or go beyond the confines of a fence. "The seed spreads around."

Most people recognize the terms "perennials" and "annuals," but biennials are the forgotten flowers of the green thumb set. Just what defines these under-used flowers?

Kim Peaver of seed company Thompson & Morgan says, "a biennial is a plant that takes two years to complete its life cycle. The first year, it produces only foliage, then dies back to the ground. The second year it comes back up and produces foliage first, then flowers, then seeds. Then it dies completely."

But why plant something that will be dead in two years?

Because biennials self-sow, there's always a plant in that spot—or close to it. By the time the mother plant dies, the self-sown plants are ready to bloom, thus providing color season after season.

"I suspect that the biennials we see commercially available each have something special about them that folks just can't get in a perennial or annual," Peaver adds. Chinese Lanterns and the Silver Dollar Plant, she says, are "well worth the wait. If you examined all the biennials that people grow, you would probably find something special about each one."

And to utterly confuse matters, some varieties of biennials are grown as perennials or annuals.

Nurseries often sell biennial plants as well as the seeds, but Kaweske cautions that "people should learn to buy green before the flowers come in." Whether you're searching for an annual, perennial, or biennial, look for a healthy plant first.

Plant these well-known species for a garden that will always be in bloom during the growing season.

Alcea rosea (Hollyhock; also known as Garden Mallow) — Plant this tall, two-to-nine-foot sentimental favorite as an accent or in back of the border in rich, well-drained soil and full sun. Don¹t sow seeds where heavy winds can knock the spikes down. To Victorians, hollyhocks symbolized fertility; the hollyhock is a heavy self-sower. Blooms: Mid-summer through part of October depending on the species. Zones 1-6.*

Campanula medium (Canterbury Bells) — Use Canterbury Bells, which grows 12 to 36 inches high, in small groups in rock gardens or borders; good for cutting (the flowers are bell-shaped). Likes rich, moist soil in full sun. Blooms: Spring into early summer. Zones 3-6.

Dianthus barbatus (Sweet William) — Prefers well-drained alkaline soil; sun or light shade. Use in edging, in containers, rock gardens, windowboxes. Grows 10 to 20 inches high. Has a sweet fragrance—hence the common name. Blooms: Late spring into summer. Zones 4-6.

Digitalis purpurea (Foxglove) — Grows 2-3 feet high in rich soil with good drainage. These striking flowers don¹t do well in heat. Also, all parts of this light-shade lover are poisonous, so while you might eat the daisies, don¹t eat this plant. Hummingbirds love the flowery spikes, and alas, so do slugs. Blooms: From June to July. Zones 4-6.

Lunaria annua; L. biennis (Money Plant; also known as Honesty, Moonwort, White Satin) — Grows 1 to 3 feet in poor soil. Good for dried arrangements. This tough plant with purple or white flowers does fine in sun, but prefers some afternoon shade when it gets hot. Blooms: Late spring to early summer. Zones 1-6.

Matthiola incana (Stock) — Often grown as an annual, this hardy biennial with a strong fragrance reaches 12 to 30 inches, and is good for borders, beds, containers. Sow indoors, then transplant to moist, well-drained soil; full sun or light shade. Doesn¹t like the heat, so make sure its new home is cool. Blooms: Summer into autumn. Zones 1-6.

Myosotis sylvatica (Forget-Me-Not) — Likes fertile, moist well-drained soil. Partial sun preferred, but full sun is okay. This abundant reseeder with tiny blue flowers grows just 6 to 12 inches. Blooms: Late spring, summer, fall. Zones 5-6.

*Zones reflect DIG IT! territory.

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published August 01, 2003