The Unexpected Delight of Fall-Blooming Bulbs

Ah, autumn, when hardy flowering bulbs appear in garden centers, enticing gardeners to plant now in anticipation of a reward six months later, when those quintessential harbingers of spring begin to appear in the garden: snowdrops, crocuses, daffodils, tulips, and all the rest.

But, for savvy gardeners, autumn’s arrival brings an additional delight in the form of hardy bulbs that flower in fall – no need to wait months for flowers. Blooms in shades of rosy pink, lavender, purple, white, and golden yellow complement the seasonal foliage and flowers of fall, showcased at ground level in your garden. For bulbophiles, gardeners (like me) who love flowering bulbs in any season, it’s an opportunity to try something a little out of the ordinary, something unexpected.

The most well-known fall-blooming bulbs include meadow saffron (Colchicum), autumn-flowering crocus (Crocus spp.), and autumn daffodil (Sternbergia lutea), all of which I have grown in my garden. In my research, I came across two additional fall bloomers, autumn snowflake (Acis autumnalis) and Japanese onion (Allium thunbergii), both of which sound intriguing, lovely, and therefore irresistible to a bulbophile.

Fall-blooming bulbs turn the seasons around. You may be familiar with the seasonal cycle of hardy spring bulbs: planting in fall, with first leaves and then flowers appearing in spring, then dying back for a period of summer dormancy underground. With fall-blooming bulbs, the cycle is reversed: planting in late summer, first flowers emerging in fall, then foliage appearing, either along with or after the flowers, then dying back for a period of summer dormancy underground.

Care and Cultivation

Because they are ready to grow right now, fall-blooming bulbs do not keep as well on store shelves in the fall as spring bulbs do. This means they are not as commonly available at garden centers, but check for them as soon as the bulb displays are put out in late summer. You may also need to seek them out through online bulb specialists and order them as early as possible to allow time for planting in summer while the bulbs are still dormant.

Fall-blooming bulbs should be planted promptly, as soon after you acquire them as possible. Do not let them sit around until November while you finish all your other fall garden tasks first, so it is a good idea to know where you will plant them before they arrive at your garden. Colchicum corms are notorious for flowering while still in their bag or box on the shelf. If that happens, remove any flowers before planting in the ground.

Most fall-blooming bulbs require good to excellent drainage; no soggy soil, especially during the summer months. Adding some grit or crushed stone to the planting area may help with drainage and hinder rodents at the same time. With the exception of autumn-flowering crocuses, though, the fall-bloomers mentioned in this article are considered deer- and rodent-proof.

Because most fall-blooming bulbs originate in climates with hot, dry summers, they grow best in full sun. Dryness during summer dormancy is considered essential – something that may be difficult to achieve and out of our control during excessively wet summers. Even so, most of my fall-bloomers have survived for years, even as shade has increased over time.

The leaves of fall-blooming bulbs are produced either just as the flowers appear, or after the flowers have bloomed. Indeed, sometimes foliage doesn’t appear until the following spring, long after the flowers have disappeared. The foliage is essential to replenish the bulbs for future growth, so it must be left in the garden to naturally die back. For some bulbs, such as crocuses, the thin leaves are unobtrusive as they fade away and do not present a visual or design problem. But others, such as colchicums, have much larger, floppy leaves that do not age gracefully and may last until mid-summer. Because of this, it is often recommended to place fall-blooming bulbs at the base of shrubs or plant them amongst groundcovers, where their foliage will not smother more delicate perennials.

Bulbs can be lifted and replanted elsewhere during their summer dormancy, especially if flowering diminishes or growing conditions change. For the showiest floral displays, however, it is best to leave them undisturbed to increase in size and spread. Many will form offsets (small bulbs) that can be dug and replanted. Some will self-sow.

The Best Fall-Blooming Bulbs

Autumn daffodil (Sternbergia lutea) is my favorite fall-blooming bulb, a small goblet of rich golden yellow set on a stem about 6 inches high. It begins blooming in September, lasting for several weeks. Glossy, green, strap-like foliage appears with the flowers, stays evergreen through the winter months, and does not disappear until early summer. It looks similar in shape and size to a crocus, but it is more closely related to daffodils. Most of the references suggest it is hardy in USDA Hardiness Zones 7 to 9 and can be somewhat fussy in cultivation. But my Sternbergia apparently has not read the literature, for it has survived in my Zone 6 garden for years in dryish, partial shade. Plant bulbs about 6 inches deep in full sun and well-drained soil.

Autumn-flowering crocuses (Crocus speciosus and many other species, varieties, and cultivars) have small, delicate flowers in shades of purple, lavender, or white. Planting in groups ensures a vibrant display of color. John Bryan, in his excellent reference book Bulbs (Timber Press, 2002), comments that "Although [crocuses] are a symbol of early spring, many species in fact flower in autumn." In addition to the more readily available C. speciosus, which flowers in mid-autumn and is noted for its showiness, hardiness, and tolerance of summer moisture, there are numerous other fall crocus species that can extend the flowering season from early to late autumn and even into the winter months (with protection). Fall-flowering crocuses grow best with full sun and excellent drainage and should be planted 3 to 4 inches deep. Fall-blooming Crocus sativus, better known as saffron crocus, is the source of the expensive orange spice and vibrant scarlet dye.

Fall-flowering Colchicum species have many common names, including two: autumn crocus and meadow saffron, which can be misleading to gardeners. Although colchicums may resemble crocuses, they are not related as they belong to different plant families. John Bryan to the rescue: "Just look at the color: colchicum flowers are pinkish or rose lavender (although white forms exist), whereas fall-blooming crocuses are blue-lavender or white." Two other common names, naked ladies and naked boys, refer to the fact that the flowers appear without leaves. The flowers are larger than fall crocuses, up to 6 inches long, and one corm can produce multiple flowers. Plant the corm 2 to 3 inches deep in full sun and well-drained soil. Colchicums need a bit more moisture, except during dormancy, than other fall-blooming bulbs, and can tolerate some light shade. All parts of the colchicum plant are poisonous to humans and animals; wear gloves and handle with care when planting.

And Two to Grow On

Autumn snowflake (Acis autumnalis, syn. Leucojum autumnale) is a small plant, 4 to 8 inches tall. It is native to the Mediterranean area, where it grows on dry, rocky slopes in areas of full sun and excellent drainage. The cultivar 'September Snow' is rated hardy to USDA Hardiness Zone 6, possibly colder, according to Plant Delights Nursery.  The small, pendent bell-like flowers are white in color and sometimes tinged with pink. They dangle from wiry reddish stems, appear in September, and are followed by grassy tufts of thin, dark green foliage.

Japanese onion (Allium thunbergii) is a clump-forming ornamental onion, native to parts of eastern Asia. It flowers from September into November with globe-like clusters of bright pink to purple flowers, each with prominent orange stamens. It is hardy in USDA Hardiness Zones 4 to 9. The attractive, green, grass-like foliage looks nice from early summer on, turning rusty orange in color after frost. The cultivar ‘Ozawa’ is more compact, reaching just 6 to 12 inches in height, and has more and larger flowers than the species. Plant in full sun to light shade, in average, well-drained soil.

Both of these fall-blooming bulbs would look great in a rock or alpine garden, along the edge of a stone wall, or as an edging plant, where their delicate, late-season beauty can be enjoyed up close. Both are also new "finds" for me, and I am excited to think about adding them to my garden. That is the unexpected delight of gardening in every season.