Bulbs

Iris (bulbous)
iris

- Height 4-27 in (10-67 cm)
- Planting distance 2-8 in (5-20 cm)
- Flowers early winter to late spring or early summer to midsummer
- Well-drained soil
- Sheltered, sunny site
- Bulbs available early fall to midfall
- Hardiness varies with species; generally reliable zones 5-9

The irises in this group all grow from bulbs, unlike bearded and beardless irises, which are rhizomatous. The species bulbous irises, which flower in winter and spring, are the smallest and ideal for pockets of soil in a rock garden, the front of a border, or bare ground under deciduous shrubs. The hybrids, which appear in early summer and midsummer, make good cut flowers, as they are taller and have larger flowers. Most bulbous irises prefer light, well-drained soil (ideally alkaline) and a sheltered, sunny site.

Popular species and cultivars
Iris bucharica has up to seven sweetly scented cream and yellow flowers on 11/2 ft (45 cm) high stems. These appear in mid- and late spring. This iris grow best in light, well-drained soil containing humus and some lime. An ideal site is below deciduous shrubs or trees, which will shelter the plants and keep them dry in summer. Plant the bulbs 6 in (15 cm) apart in early fall. Iris danfordiae has vivid lemon-yellow flowers, which appear in mid- and late winter in the southern part of its range and in early spring in the North. The plants only 4 in (10 cm) high, and the flowers have an attractive honeylike scent. Hardly any leaves are evident at flowering time. Plant bulbs 2-4 in (5-10 cm) apart in light, well-drained chalky soil and full sun. Iris histrioides 'Major' has bright royal blue flowers, each with a yellow central ridge on the falls. It is one of the earliest bulbous irises appear, flowering in early winter to midwinter in the South and early spring in the North. The plant is extremely hardy, with blooms that can remain unscathed through frosts and snow. At flowering time the leaves are only 1 in (2.5 cm) high, but by spring they may have reached 11/2 ft (45 cm). As the flower stems are just 5 in (13 cm) high, they look most effective grown as a mass in a rock garden. This is a useful species for the garden since it is one of the few small bulbous irises to tolerate dappled shade. Set the bulbs 2-4 in (5-10 cm) apart in light, well-drained alkaline soil. Iris reticulata has deep violet-blue flowers with a gold spot in the center of each fall. The flowers appear in late winter and early spring (depending on the climate) and are accompanied by a taller leaves. This species and its cultivars are 6 in (15 cm) high and should be planted 2-4 in (5-10 cm) apart. 'Joyce' (sky-blue), 'Katharine Hodgkin' (large, pale blue and yellow), 'Natascha' (white and blue, yellow markings), and 'Pauline' (violet, white and blue variegated blotches) are popular cultivars. Iris xiphium, a tender Mediterranean plant, is the main species from which three types of hybrids have been developed.
Dutch hybrids flower in late spring. Their colors range from white, yellow, and blue to purple. The plants reach 15-24 in (38-60 cm) high. Set bulbs 4-6 in (10-15 cm) apart in light, fertile soil in a sunny site.
English hybrids are the last of the bulbous irises to flower, coming out in early summer. They have the largest flowers, but smallest color range: whites, blues, pinks, and purples that are often flecked. The plants reach 15-27 in (38-67 cm) high and should be set 6-8 in (15-20 cm) apart in rich soil.
Spanish hybrids flower between the Dutch hybrids and English hybrids in late spring to early summer. The fragrant blossoms come in a good color range, including smoky shades: whites, browns, blues, purples, and mauves. The plants stand 1-11/2 ft (30-45 cm) high. Set the bulbs 6-8 in (15-20 cm) apart in light soil in a sunny spot.

Bulbs