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Home » Gardening Information » Great Plants

Cool-Season Annual Herbs—Charming Candidates for the Spring Garden

Plants & Gardens News Volume 17, Number 1 | Spring 2002

by Alessandro Chiari

For many centuries, we humans have harvested and processed herbs for utilitarian purposes, for use as flavorings, medicines, dyes, oils, and perfumes. But we've also cultivated a number of them for their ornamental features, for the beauty of their flowers or foliage. Among these ornamentally significant herbs, the annuals are my favorites.

I prize annual herbs for the same reason a gardener prizes any annual plant—they're versatile, easy to grow, and they bloom continuously and profusely throughout the season. Some annuals have undergone intense selective breeding for flower size and color, to the point of becoming gaudy. But the annual herbs have maintained their old-fashioned balance and charm. When used as ornamentals in a mixed planting scheme, they complement perennials rather than overwhelm them.

The following herbs belong to a group called cool-season annuals—also known as spring or hardy annuals. They can be sown or planted out in early spring and will thrive from spring to summer. Unlike violas, pansies, and other common cool-season annuals, these herbs are difficult to find for sale as plants and so, more often than not, they must be grown from seed. Designing a garden with them also becomes an adventure in the venerable art of seed collecting, saving, and germinating.

Linum usitatissimum (Common flax)

Since biblical times, common flax has been cultivated for its fiber, which can be used to make linen cloth, and for its seed oil (linseed oil). Originating in the Mediterranean region, it belongs to the Linaceae or flax family. The plant is single-stemmed, with narrow, grayish-green leaves, and it grows from two to three feet tall. Lovely blue flowers appear on long stalks at the tip of the plant from late April to late June. Mature fruits consist of dried capsules containing about ten seeds each.

Common flax is relatively disease-free and easy to grow. It prefers rich, well-drained soil but will adapt to almost any conditions. Plant it in full sun to partial shade. Seeds can be sown directly in the garden in early spring, or they can be started indoors. Seedlings are very vigorous and produce a strong taproot, so they should be moved from their germination trays into bigger pots or into the garden as soon as possible. If you start the seedlings indoors, transplant them outside after the last spring frost. Seeds can be collected and stored when the fruit capsule is dry and has a papery consistency. Linum seeds have a long shelf life and can be stored easily in a cool, dry place.

Nigella sativa (Black cumin)

Nigella sativa is a member of the Ranunculaceae or buttercup family. Its common names include black cumin, black seed, fennel flower, and Roman coriander. Native to Asia and originally cultivated for its aromatic seeds, the plant has great ornamental appeal. It grows from 12 to 18 inches tall and produces very finely dissected gray-green foliage. Between June and September, lovely inch-wide, solitary bluish-white flowers appear. They yield a golf-ball-size seed capsule that's divided into five compartments—each one topped with an inch-long horn. (Morticia Addams would love this plant!) Seeds can be collected when the capsule becomes dry, and they should be stored in a cool, dry place until the following spring. Black cumin is easy to grow; all it needs is full sun and well-drained average soil. If you start seeds indoors, transplant them into the garden after the last frost and they will flower in about 16 weeks. Seeds can also be sown directly in the garden throughout the spring for early- to late-summer flowering.

Nigella damascena (Love-in-a-mist)

Native to the Mediterranean region, love-in-a-mist is quite similar to black cumin (N. sativa). It has delicate, bright green threadlike foliage and a horned fruit of great ornamental value—especially in dried flower arrangements. It distinguishes itself, however, with its showier summer-blooming flowers, which are 1I inches across, bright blue, and surrounded by curved, feathery bracts (modified leaves). Several cultivars of the plant are easily available through seed catalogs. N. damascena 'Miss Jekyll' has beautiful semidouble bright blue flowers and grows about one foot tall (the straight species can grow up to two feet tall). If you prefer a white form or a rose form, try 'Miss Jekyll Alba' or 'Miss Jekyll Rose'. Plant love-in-a-mist in full sun and well-drained soil.

Carthamus tinctorius (Safflower)

Native to southern Asia, safflower has long been cultivated for the yellow dye that can be obtained from its flowers. It has also been grown extensively for use as a dried or fresh cut flower. A member of the Asteraceae or aster family, safflower has an erect, two- to three-foot-high stem with oval, spiny-toothed leaves. In summer, the stem branches at the top to produce several shoots bearing 1 1/2-inch-wide thistle-like yellow or orange flowerheads.

Safflower prefers well-drained soil and full sun. Because it doesn't like its feet wet, it's a good plant for any well-drained spot in the garden. If sown in the garden in early May, the plant will flower in July and produce seeds around September. Plants started indoors can be transplanted into the garden as early as the beginning of April. There are several cultivars available, including C. tinctorius 'Lasting White', which has creamy white flowers.

Consolida ajacis (Larkspur)

Native to southern Europe, larkspur was originally cultivated as a medicinal plant. Indeed, its genus name was derived from the plant's ability to "consolidate" and heal wounds. But larkspur has long been a very popular cut flower and garden annual. Another member of the Ranunculaceae or buttercup family, it's an erect plant, growing two to three feet high and producing fine, feathery soft, fernlike leaves. From late spring to summer, it bears many showy 1 1/2-inch bright blue flowers on upright, densely packed spikes. Larkspur prefers well-drained soils and full sun to partial shade. It doesn't respond well to transplanting, so I recommend direct sowing of seeds in the garden, which can be done quite early in spring. Late frost usually doesn't damage the seedlings. You can start collecting seeds about two months after flowering. Harvest from the dry fruits at the bottom of the flower spike first, as they contain the most mature seeds.

Larkspur is sometimes offered as C. ambigua, though its correct name is Consolida ajacis. Many cultivars available through seed catalogs have single or double flowers and colors ranging from violet to pink to white. Cultivars are usually two to three feet tall, but 'Giant Imperial' can reach four feet. Most of the garden cultivars come true to type (they look like the parent plant) from seeds collected in the garden.

Borago officinalis (Borage)

This annual is native to southern Europe and was a common medicinal plant in ancient Rome. Today borage is still grown in many herb gardens for its young leaves and flowers, which are used to flavor food. A member of the Boraginaceae or borage family, it grows up to two feet tall and one foot wide, producing six- to eight-inch-long dark green leaves covered with stiff white hairs. From late spring to late summer, the plant is covered in drooping clusters of inch-wide star-shaped sky-blue flowers, which are very attractive to bees and butterflies.

A drought-tolerant plant, borage performs best in full sun and well-drained soil. Seeds can be started indoors in midwinter and transplanted into the garden by mid-April. Borage seedlings don't like to be transplanted, so I recommend moving them from their germination trays into four-inch pots as soon as possible prior to planting them in the garden. Or just sow directly in your garden after the last frost. Seeds can be collected and stored from mid- to late summer. To the best of my knowledge, no cultivars are available except 'Alba', a white-flowering form.

Seed Sources:

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