Gladiolus Bloom Period

Plant Development

• Intolerant of frost and frozen soils, gladiola corms may remain in the ground year round in U.S. Department of Agriculture plant hardiness zones 8 through 10. Elsewhere, corms are lifted to store indoors and then planted outdoors in spring once the soil has warmed. Gladiolas are often planted the same time of year sweet corn seed is sown. Eight to 12 weeks after planting, blossoms, called florets, begin opening on the upright stem spike.

Flower Spike

• The number of flower buds that form on the flower spike varies by gladiola species or the hybrid's genetic code. The florets begin opening first on the flower spike’s lowermost part with multiple blossoms open simultaneously on display. When the oldest, lowermost florets wither, new flowers open higher up on the spike, extending the blooming display. An individual floret may last three to seven days, but the collective progression of florets on the spike may last 10 to 21 days. Cultivars that produce longer flower spikes with more florets have the longest blooming period until the last tip floret withers.

Factors Affecting Duration

• Gladiolus plants prosper in sunny locations where the soil is warm, fertile and moist but well draining. When air temperatures are cool and the days cloudy, flower spike production may be delayed, or any flower spike blooming may last longer than usual. Conversely, a warmer-than-usual season hastens flower development and blossoms may wither more quickly. This is especially true if soil is too dry or plants are not healthy leading into the flowering season. A cool weather regimen, 55 to 70 degrees Fahrenheit, prolongs the display of the flowers on the flower spike compared to hot summer days above 80 F. Cut flower stems may be held in a refrigerator about 40 to 50 F for days delaying further flower bud opening.

Cultural Insight

• Slightly larger-sized corms bloom earlier after planting when compared to smaller corms, according to the University of Minnesota Extension Service. Gardeners realize that one gladiola plant may yield an attractive, full flower spike for about two weeks. Plant corms successively in groups every two to three weeks up until 90 days before the first fall frost date in your region prolongs the flower display. Staking and tying tall gladiola flower spikes help prolong the flowering, as stem snapping or vein pinching is less likely to occur from winds or rain downpours.