Gladiolus Care Zones

Gladiolus Hybrids

• The towering stalks and large flowers that most people associate with gladioli belong to hybrid cultivars, the result of decades of crossbreeding. These tender bulbs can be left in the ground without extra care in U.S. Department of Agriculture plant zones 10 and 11. In zone 9, they survive winters if mulched in the fall. Mulching is an also an option in zones 7 and 8, but even with the insulation provided by the extra mulch, their survival is questionable in a harsh winter. To be on the safe side, dig the gladiolus corms and replant them in the spring. In zones 6 and colder, always dig the corms and store them to replant the following spring. Wherever you live, gladioli need good drainage or they will rot and die, regardless of temperature.

Butterfly Gladioli

• Butterfly glads are hybrids of G. nanus, one of the South African species of gladioli. Rather than the trumpet-shaped flowers and big splotches of contrasting color typical of large gladiolus hybrids, butterfly glads have open flowers with distinct, teardrop-shaped "darts" of color on each petal. The short stalks typically have fewer than 12 florets and come in white, pink, salmon and shades of red. Smaller and more delicate than common glads, these charming plants are hardy to zone 4 with protection.

Sword Lilies

• Commonly called sword lily or hardy gladiola, G. byzantinus is winter-hardy to zone 5. This species has 15- to 20-inch flower spikes with 1- to 3-inch flowers along one side of the stem. The dark pink flowers have long, narrow petals with lighter pink centers. G. byzantinus is one of the few gladioli tolerant of dense clay soil, but they do still need good drainage in winter.

Digging and Storing

• To save tender gladioli over the winter, dig the corms after the first frost. Cut the foliage off just above the corm and shake off excess soil. Leave the corms to cure for three weeks in a warm, dry, well-ventilated area. Once the corms are dry, gently remove the plump, upper corm from the remains of the old corm, which should be discarded. If small, baby cormels have formed around the outside of the corm, save them and plant them in a sheltered location the following spring; it will take several years for them to reach blooming size. Treat the dried corms with carbaryl to protect them from insects and store them in paper bags or old pantyhose until it's time to plant them outside again.