Gladiolus

Gladiolus corms should be planted after the last frost date when soil has warmed to at least 55°F (13°C). Choose a sunny, sheltered spot as tall spikes are vulnerable to wind damage. Plant corms 4-6 inches deep and 6 inches apart with the pointed end facing up.

For continuous blooms, practice succession planting by setting new corms every two weeks from mid-spring through early summer. This extends the flowering season from midsummer into early fall. Water regularly during active growth, providing about one inch per week, and increase watering when flower spikes begin to develop.

In zones 7 and warmer, gladiolus corms can overwinter in the ground with a heavy mulch layer. In colder regions, dig corms after the first light frost blackens the foliage. Cut stems to one inch, cure for two weeks in a warm, dry area, then store in mesh bags with dry peat moss at 35-45°F (2-7°C) over winter.

Gladiolus belongs to the iris family (Iridaceae) and encompasses approximately 300 species, the vast majority native to sub-Saharan Africa, particularly South Africa's Cape region, with a smaller number found around the Mediterranean basin and in western Asia. The genus has been cultivated since at least the 18th century, when European botanical explorers began collecting South African species and shipping corms back to the gardens of Holland, England, and France. The first recorded hybrid gladiolus, Gladiolus × colvillei, was created in 1823 by crossing G. tristis with G. cardinalis, producing a plant with larger flowers and more vigorous growth than either parent. Throughout the 19th century, breeders in Belgium, France, and later the United States developed increasingly showy hybrids by crossing multiple South African species, eventually producing the large-flowered grandiflorus hybrids that dominate gardens and the global cut flower trade today. By the early 20th century, gladiolus had become one of the most commercially important flower crops worldwide, with thousands of new cultivars registered each decade. The plant played a significant cultural role during the Art Deco period, when its tall, architectural form made it a symbol of elegance and modernity. In South Africa, wild gladiolus species remain ecologically important as food sources for specialized pollinators, and many are now protected under conservation legislation due to habitat loss from agriculture and urbanization. Today, the Netherlands, Israel, Japan, and the United States are the leading producers of gladiolus corms and cut flowers, with annual global production estimated at billions of stems.

Gladiolus performs best in well-drained, sandy loam soil with a pH of 6.0-6.5. Heavy clay must be amended with coarse sand and compost to prevent waterlogging, which causes corm rot. Work a balanced 5-10-10 fertilizer into the soil at planting time. Side-dress with a high-potassium fertilizer when flower spikes begin to emerge, and again after flowering to help corms build reserves for next season.

Cut gladiolus for arrangements when the lowest two or three florets on the spike have opened and the remaining buds show color. Cut in the early morning using a sharp, clean knife at an angle. Leave at least four leaves on the plant to feed the corm for next year. Place stems immediately in warm water with floral preservative. Buds will continue opening up the spike over 7-10 days in the vase.

After the first light frost, cut foliage to one inch above the corm. Dig carefully and shake off loose soil. Cure in a warm, dry, well-ventilated area for two to three weeks. Remove the old shriveled corm from beneath the new one and discard. Dust with fungicide powder and store in mesh bags or open trays at 35-45°F (2-7°C) with low humidity. Check monthly for rot or dehydration through winter.