Spring-flowering bulbs, such as tulips and daffodils, are familiar to all gardeners. Though not widely planted, there are several fall-blooming bulbs that are a welcome addition to the fall garden.
Colchicums
Colchicums (Colchicum spp.) arise from bulb-like corms. The leaves of most colchicums emerge in early spring and die back by early summer. White to pink to purple, crocus-like flowers appear without foliage in fall. They are also known as autumn crocuses.
Colchicums should be planted immediately upon receipt in late summer or early fall. (If not planted immediately, the corms often bloom during storage.) Plant corms in well-drained soils in full sun to partial shade. Good planting sites include naturalized areas under the filtered shade of large trees and shrubs, in rock gardens, or amongst low-growing groundcovers such as vinca (Vinca minor). For the best visual display, plant colchicums in clumps. Corms should be planted 2 to 3 inches deep and 6 inches apart.
Gardeners can choose from several excellent cultivars. 'Album' produces pure white flowers. 'Alboplenum' has double, white flowers. The flowers of 'The Giant' are 10 to 12 inches tall and violet with a white throat. 'Lilac Wonder' bears large, rosy-purple flowers. 'Pleniflorum' has double, rose-pink flowers. 'Waterlily' produces double, lilac-pink flowers which resemble a water lily.
Colchicums are native to Europe and northern Africa. The scientific name comes from Colchis, an ancient country bordering on the Black Sea, now part of the Georgian Republic, where colchicums are abundant.
The dried corms and seeds of Colchicum autumnale are the source of medicinal colchicum. It is also the source of colchicine which is used in plant breeding to induce polyploids.
Autumn Crocus
Several species of the spring favorite crocus bloom in the fall. Collectively referred to as autumn or fall crocus, these species all grow in similar conditions and require similar care. Plant corms as soon as they are available in late summer or early fall. Plants perform best in partial to full sun in a well-drained soil. Possible planting sites include rock gardens, naturalized areas, and perennial borders. Plant corms 3 to 4 inches deep in groups of 25 or more. All are hardy to USDA hardiness zones 3 to 8.
Showy Crocus
Another attractive fall-blooming bulb (corm) is showy crocus (Crocus speciosus). Flowers are violet-blue with yellow anthers and deep orange stigmas. Plant height is approximately 5 to 6 inches. Excellent cultivars include 'Albus' (white flowers), 'Cassiope' (aster-blue flowers with yellow bases), 'Conqueror' (clear, deep blue flowers), and 'Oxonian' (large, dark blue flowers). Showy crocus blooms in late September or October.
Autumn Crocus
Autumn crocus (Crocus kotschyanus) has 2 to 3-inch-tall pale violet flowers with darker veins. They need dry summer conditions to thrive. Flowers typically appear in September. Plants are native to Turkey and the Caucasus.
Also called autumn crocus, Crocus medius has 3-inch-tall pale to dark purple flowers with brightly contrasting orange to almost red stamens. Native to France and Italy.
Hairy Crocus
The rather unattractive common name, hairy crocus (Crocus pulchellus), comes from the hairy filaments (stalks) that hold up the anthers. Flowers are actually quite attractive at 4 to 5 inches tall, with pale lilac-blue flowers with darker veins. Plants are Mediterranean natives.
Ornamental Onions
Most ornamental onions, or alliums, bloom in late spring and early summer. Their globe-shaped flower clusters are unmistakable. Those that bloom in the fall tend to have small or poorly formed bulbs on rhizomes that allow the plant to form dense clumps of foliage and flower stalks. Unlike many spring-blooming species where foliage dies back just before or after bloom, the fall-blooming ornamental onions have green foliage all year.
Grow in fall or part sun in moist, well-drained soils. Plants are hardy to USDA Hardiness Zones 4 to 8.
Japanese Onion
Japanese Onion (Allium thunbergii) grows 18 to 24 inches tall with flowers that appear in September and October. The globe-shaped flower clusters are 1 to 1.5 inches across and are comprised of small purple to pinkish purple flowers. The cultivar 'Ozawa' is frequently planted because of its superior flower color. So much so that it is rare to see anything but that cultivar in garden settings.
Garlic Chives
Grown for both ornamental and culinary purposes, the flat linear leaves of garlic chives (Allium tuberosum) have a distinct onion-y, garlic-y flavor. Small star-shaped white flowers are arranged in globe-shaped flower clusters about 2 inches wide. Plants will self-seed aggressively, spreading around the garden with abandon. Deadhead just as the flowers fade to reduce the spread of the seed.
Formosa Lily
With a good selection, you can have true lilies (Lilium) blooming in your garden from June to September. This diverse genus is best known for its summer-blooming Asiatic and Oriental hybrids, as well as martagon (Turk's cap) and Easter lilies. There are a few species, however, that bloom rather late in the season, the most notable being the formosa lily (Lilium formosanum).
As with other lilies, the Formosa lily grows in full sun and well-drained soil. Plants tend to be tall, so they are best nestled in the back or middle of the border. Flowers are white, trumpet-shaped, and 3 to 8 inches long. Once finished blooming, remove the spent flowers to allow plants to focus on building bigger bulbs (and blooms) next year instead of seeds. Bulbs are hardy to USDA Hardiness Zones 5 to 8.
Autumn Snowflake
Autumn snowflake (Leucojum autumnale) looks much like the more familiar spring and early summer blooming species. Plants are much shorter than L. aestivum and L. vernum, standing only at 6 to 8 inches with much narrower, more grass-like foliage. Much like the flowers, the foliage comes up later in the season. White, bell-shaped flowers appear in August or early September, about one-half inch across, and may have a slight rosy color. Native to Europe and northern Africa grow in full sun or light shade in exceptionally well-drained soils. Hardy in USDA Hardiness Zones 5 to 9.