In autumn, when deciduous trees in the Northeast turn radiant colors of red, purple, orange and yellow, most gardeners think about planting spring-flowering bulbs such as tulips, hyacinths and daffodils in their garden. When in bloom, these bulbs offer dramatic color at a time of year when the rest of the landscape is relatively dormant.
Showy summer-flowering bulbs—collectively including corms, rhizomes and tubers—are planted in the spring, when soils warm and gardening is once again on our minds. These low-maintenance jewels, which include crocosmias, dahlias, begonias, gladioli, lilies and others, have much more competition from annuals and perennials and even woody plants, yet they provide gardeners an opportunity to strategically embellish the landscape by tucking them into spots for a burst of color, a contrasting shape, or a bit of height and texture.
When to Plant
Summer-flowering bulbs are planted in mid- to late spring as soon as the danger of frost has passed and the soil temperatures have warmed to 65°F. Tender spring-planted bulbs—USDA hardiness zone 6 and above—will not survive the cold Northeast winters; to preserve these bulbs, gardeners must dig them up in the fall and properly store them over winter.
Where to Plant
Similar to many other plants, bulbs prefer to grow in loose, well-drained soil that is amended with compost or other organic matter. But it’s the planting depth of bulbs that is crucial. The general rule of thumb is to plant them three times as deep as the bulb is tall. Light conditions are also important and vary depending on the type of bulb. Begonias, for example, prefer shady conditions; dahlias prefer full sun. Summer-flowering bulbs can be planted en masse in a landscape for visual impact or showcased in containers. And they make wonderful additions to border, perennial and rock gardens.
Rare & Unusual Bulbs
The visual beauty that comes from a garden that is artfully planted with summer-flowering bulbs is undeniable. There are thousands of types from which to choose. If you are looking to stand out from your neighbors and go beyond what the big box stores have to offer, consider rare and unusual bulbs. It’s such a joy for both novice and discerning gardeners alike to grow bulbs that have history. Rare varieties are typically harder to find in the United States or are at least limited, but there are small specialty nurseries and online companies that offer limited amounts of rare varieties. And unusual doesn’t necessarily mean hard to grow, just that they offer something out of the ordinary, like a unique bloom shape, color or foliage. The fact is, many of the rare heirloom bulbs prosper with minimal care and attention.
Dahlias are a favorite summer-flowering bulb. These showy plants add drama to any garden with their bright colors and playful blooms of varying shapes and sizes from petite to as large as a dinner plate. One of the most charming white dahlias to grow is the rare ‘White Aster’. This heirloom is considered one of the world’s oldest surviving garden dahlias. First introduced in 1879, it produces masses of small, pristine ivory-white globes summer through fall. It’s easy to grow and makes an excellent cut flower. Another special one to seek out is the creamy white ‘Tsuki Yori No Shisha’, which translates as “messenger from the moon.” With six- to eight-inch blooms, this showstopper is deeply fringed and shaggy and makes a wonderful addition to a white garden.
Also on the list of favorite summer-flowering bulbs are gladioli. Victorian gardeners including French impressionist painter Claude Monet adored the dramatic spikes of color this plant offered in the summer garden, often rising three to four feet tall. Monet’s 1876 painting Corbeille de fleurs features a flower garden where gladioli dominate the composition.
Gladiolus blooms are seldom fragrant, so adding ‘Murielae’ to your garden gives you scent and ivory flowers with dark purple throats that sway on arching stems. Best grown in full sun, this graceful mid- to late-summer bloomer is sweetly fragrant and ideal for cottage-style and cut-flower gardens. Plus, it’s adored by hummingbirds and disfavored by deer.
If you have a shady spot in your landscape and are looking for extravagant color, consider planting tuberous begonias. These elegant plants, a bit trickier to grow, have attractive foliage and rose-like flowers that bloom from mid-summer to frost. The upright growth habit of these plants make them ideal for container and garden beds. The cascading types are perfectly suited for hanging baskets. Begonia bulbs can be directly planted in the garden in the spring with no more than an inch of soil covering them. For earlier blooms, start your begonias indoors, six to eight weeks before the last frost date. If you love orange, consider planting begonia ‘John Smith,’ named after its creator. The result of Smith’s labors is a large, flowering, softly fluted, scented, double begonia of exhibition quality from Blackmore & Langdon in England.
Now is the perfect time to plan for the upcoming gardening season and consider how you’ll incorporate some summer-flowering bulbs into your landscape. They will add unique interest, color and even fragrance to your landscape during the hottest months of the growing season.