Sword flowers, commonly known as Gladiolus, are popular in gardens and cut flower arrangements. Their tall, upright flower spikes and sword-shaped foliage give them their common name. These blooms add a vertical element to any setting, making them a favored choice for visual impact.
Understanding Sword Flowers
Gladiolus plants have narrow, sword-like leaves that grow in an upright fan. From these fans emerge flower stalks, which can reach heights of 2 to 5 feet. Each stalk has numerous funnel-shaped flowers that open sequentially from the bottom upwards.
Gladiolus colors are broad, encompassing nearly every hue, from vibrant reds, pinks, and yellows to purples, oranges, and whites, with some varieties featuring bi-colors or ruffled petals. This range makes Gladiolus versatile for garden designs and floral displays. While some wild species exist, the large flower spikes seen today result from centuries of hybridization.
Planting and Cultivation
Site Selection and Soil
Gladiolus thrives in full sun, ideally six to eight hours daily, for best blooms. While they tolerate partial shade, colors may be less vivid. Well-draining soil is important, as corms rot in soggy conditions. Incorporating compost or organic matter improves drainage and provides nutrients. Gladiolus prefers a slightly acidic to neutral soil pH.
Planting Corms
Plant gladiolus corms in spring after the last frost, when soil temperature reaches at least 55°F (13°C). For continuous blooms, plant corms every 10 to 14 days from late spring until early July. Plant corms 4 to 6 inches deep, pointed end upwards, and spaced 6 to 8 inches apart. For a fuller display, plant corms in groups of seven or more.
Watering and Fertilizing
Consistent moisture is important, especially during dry spells and active growth. Gladiolus requires about 1 inch of water per week; deep watering encourages strong root development. A 2 to 4-inch layer of mulch helps retain soil moisture and suppresses weeds.
Adding compost before planting provides a good base. Apply balanced fertilizer when plants are about 10 inches tall, and high-potash fertilizer before flowering to promote blooms.
Staking
Staking is often needed for taller gladiolus varieties to prevent heavy flower spikes from flopping due to wind or bloom weight. Install stakes early in the growing season, soon after planting, to avoid damaging corms or developing stalks.
As the stalk grows, loosely tie it to the stake with soft material or use support rings. Grouping plants or planting them near other sturdy plants can also offer natural support.
Common Pests and Diseases
Gladiolus can be susceptible to pests and diseases, though proactive measures help manage them. Thrips, particularly Gladiolus Thrips, cause silvery streaks on leaves and distorted, discolored flowers. Aphids feed on sap, leading to stunted growth and sticky residue. Regular inspection and appropriate controls can mitigate infestations.
Botrytis blight (Gladiolus Scab) manifests as brown spots on leaves and flowers, and can cause corm rot. Fusarium wilt causes yellowing foliage and wilting, often leading to plant death. Good air circulation, proper spacing, and well-drained soil prevent fungal diseases. Inspecting corms for damage or rot before planting is also a preventative step.
Harvesting and Using Cut Flowers
Harvesting gladiolus for cut flower arrangements at the optimal time extends their vase life. Cut stems in the early morning when plants are most hydrated. Select stalks where the lowest one or two florets have just opened, with remaining buds closed. This allows upper buds to open gradually in the vase, providing a longer display.
Use a sharp knife or floral shears for a clean, angled cut. Immediately place cut stems into lukewarm water to prevent air pockets, which hinder water uptake. When cutting, leave at least four leaves on the plant for the corm to photosynthesize and store energy. Before arranging, remove foliage below the waterline, as submerged leaves rot and encourage bacterial growth, shortening lifespan. Changing water every couple of days and adding floral preservative prolongs freshness.
Winter Care and Corm Storage
In colder climates (USDA Zones 7 and below), gladiolus corms are not winter-hardy and require lifting and storing indoors. After the first light frost, or when foliage yellows and dies back (typically six weeks after blooming), corms are ready to be dug up. Carefully lift the plant, shake off excess soil without washing corms, and trim the stalk to 1 to 2 inches above the corm.
Allow corms to cure in a warm, airy location out of direct sunlight for two to three weeks. Curing dries and hardens outer layers, protecting them during storage. After curing, remove remaining soil and discard the old, shriveled corm at the base of the new one. Store healthy, new corms in mesh bags or breathable containers in a cool, dark, well-ventilated area where temperatures remain between 35°F and 50°F (2°C to 10°C). In warmer climates (USDA Zones 8 and above), gladiolus corms can often be left in the ground to overwinter, sometimes with a protective layer of mulch.