Like their spring-blooming counterparts, summer-flowering bulbs (as well as corms and tubers) are essentially programmed to flower during the warmest months: Plant them in the right spot, water them regularly, and they will bloom freely. In most regions, summer bulbs can be grown as annuals so even northern gardeners can enjoy unusual flowers such as those of Galtonia and Ornithogalum, which thrive in midsummer when other flowers are fading.
Summer Bulb Sampler
Tuberous begonias are easy to grow and bear showy flowers above heart-shaped leaves all season. Plant them in pots or beds to brighten a shady spot.
Cannas, grown for their lush tropical foliage topped by bold flowers, tolerate water-logged soil and also do well in regular garden soil. 'Stuttgart' is prized for its variegated foliage; 'Los Angeles' has bright pinkish-red blooms with yellow centers.
Dahlias, available in a range of flower colors, sizes, and shapes, bloom from late summer to frost. Choose 'Bednall Beauty' or 'Ellen Huston' with burgundy foliage, or the more traditional, pink-flowered 'Park Princess,' a cactus dahlia, and 'Garden Wonder,' a dark-red decorative dahlia.
Foxtail lily (Eremurus robustus), hardy to Zone 6, bears distinctive 4-foot spikes of tiny pale-pink flowers with yellow stamens in early to midsummer.
Galtonia species, native to South Africa, bloom in late summer when many other plants begin to fade. Plant Galtonia candicans singly to focus attention on its graceful, loose flower spikes and teardrop-shaped silhouette.
Gladioli, with tall spikes of funnel-shaped colorful flowers, are ideal for cutting gardens. 'White Prosperity' has pure-white blooms on 3-foot spikes, versatile enough for many arrangements. For a steady supply of cut flowers, plant corms every 2 weeks from spring to early summer.
Spider lilies, or ismene (Hymenocallis x festalis), tolerate part shade and bear dramatic, narcissus-like blooms with a heady fragrance.
Lilies, with their dazzling fluted flowers, have been a garden mainstay for centuries. 'Citronella,' an Asiatic lily hardy to Zone 3, bears up to 30 cup-shaped, bright-yellow blooms in midsummer. 'Journey's End,' an Oriental lily hardy to Zone 3, has large, intensely fragrant, deep-pink flowers that bloom late in the season.
Star-of-Bethlehem (Ornithogalum arabicum) is grown for its dense clusters of delicate flowers that are extremely long lasting in cut bouquets. 'Mount Everest' has cup-shaped pure-white blooms amidst lush green foliage. Giant chincherinchee (O. saundersiae), with its unusual common name, reaches 3 to 4 feet and bears large umbels of creamy flowers with green-black eyes.
Summer Bulb Basics
Generalizing about summer bulbs is difficult because the group is so diverse. Most are tender (not hardy) or marginally hardy but can be grown as annuals in Zone 7 and colder, where they should be planted in spring after all danger of frost has passed and the soil has warmed.
In the mild-winter regions (Zone 8 and warmer), most summer bulbs behave as perennials (left in the ground) and should be fertilized and treated similarly. To overwinter bulbs like dahlias and gladioli where they are not hardy, begin reducing water in early fall and cut back foliage after the fall frost. Then carefully dig up bulbs, and store them in a box of sand or peat in a cool (40 degrees to 50 degrees) place with a stable temperature until spring. In the North, consider growing summer bulbs in pots that can be brought indoors in fall.