UNITED STATES—Spring bulbs are making a comeback from their unceremonious internments last autumn. Some of the earlier sorts are visibly extending foliage above the surface of the soil. A few narcissus, daffodil and crocus are already blooming! Now it is time to plant late bulbs, or summer bulbs, which start to grow through warm spring weather, and bloom for summer.
Spring bulbs are generally the same as hardy bulbs of climates with cold winter weather. They are hardy to frost while dormant. Since chill is relatively mild locally, their hardiness is irrelevant. Conversely, some prefer more chill than they experience locally. Inadequate chill can compromise performance. Autumn planting maximizes their brief chill exposure.
Late bulbs are completely different from spring bulbs. Not only do they not require chill to perform, but some dislike it. Many of the most popular late bulbs that can naturalize here succumb to frost elsewhere. Instead of early planting for chill, as spring bulbs prefer, late bulbs prefer late planting to avoid chill. Their foliage emerges after the last threat of frost.
Many late bulbs are not as vulnerable to frost as they seem to be.
However, although they do not need or even appreciate chill, most popular late bulbs are resilient to the minor chill of local climates. Once established, they simply die back to the ground in response to the first frost of autumn. They maintain dormancy through winter to regenerate for spring. Some repeat this process for years, since the soil does not freeze.
Not all late bulbs are actually bulbs. Most are corms, rhizomes, tubers, tuberous roots, or other bulb-like perennials. Some, such as dahlia and canna, bloom through an extensive season. Some, such as lily and gladiolus, bloom only once. Planting in phases for a few weeks prolongs their bloom. Of course, they will synchronize for any subsequent bloom.
Canna and common white calla are two of the most reliable late bulbs. Crocosmia is too reliable, and since it can be invasive, it is rarely available. Common gladioli and various lilies are spectacular in bloom, but not reliably perennial. Dahlia is a very rewarding and reasonably reliably perennial summer bulb. It is spectacularly variable in color, form and texture.
Although they will not bloom until summer or autumn, gladiolus are in season now. Their corms, which are like bulbs, are now available from nurseries, and are ready for planting. Unlike earlier spring bulbs, they need no chill, and should not generate new foliage until warmer spring weather. Corms prefer to be at least four inches deep, in sunny situations.
The most popular and common gladiolus, Gladiolus X hortulanus, are hybrids of several species. They bloom more impressively than their simpler parents but are not as reliably perennial. Most corms bloom for only a single season, although some within each group may bloom for a second season or more. Blooms can get heavy enough to need staking.
Bloom can be bright or pastel hues of any color except true blue, perhaps combined with another related color. Individual florets are not large, but they share their floral stalks with several similar florets that bloom upward from the bottom. Long and pointed leaves stand upright, flaring only slightly to the left and right. The tallest gladiolus can get six feet high.
Horticulturist Tony Tomeo can be contacted at tonytomeo.com.