The ‘Black Surprise’ gladiolus, often called a sword lily, offers a striking addition to any garden with its deep, captivating blooms. This guide provides information on cultivating these remarkable plants, ensuring they thrive and display their full beauty.
Unveiling the Black Surprise Gladiolus
The ‘Black Surprise’ gladiolus is distinguished by its intense, velvety, darkest burgundy-red flowers, which can appear almost black in certain light. These blossoms are arranged symmetrically on strong, erect spikes, creating a commanding vertical accent and adding significant height to borders. The plant typically grows to a height of 3 to 4 feet (90-120 cm), with some varieties reaching up to 50 inches. Each flower spike can hold at least 12 buds, opening sequentially from the bottom to the top, providing a display for up to two weeks on a single spike. This cultivar is highly valued both as a cut flower, offering a long vase life, and as a dramatic focal point in garden beds.
Planting Your Black Surprise Gladiolus
Plant ‘Black Surprise’ gladiolus corms in spring, after the last frost has passed. Soil temperature should ideally be around 60°F (15°C) before planting. These gladioli thrive in full sun, requiring at least six to eight hours of direct sunlight daily, and prefer a sheltered location to protect their tall spikes from wind damage. Well-drained, fertile soil is suitable; incorporating organic matter like compost or aged manure improves soil quality and drainage.
Loosen the soil to a depth of 12 to 15 inches. For large blooms, select corms at least 1¼ inches in diameter. Plant corms with the pointed end upwards, approximately 4 to 6 inches deep; planting deeper provides better stability. Space individual corms about 6 to 10 inches apart. For a continuous display of blooms throughout the summer, consider staggered planting by planting new corms every two weeks from late spring until early July.
Ongoing Care for Black Surprise Gladiolus
Consistent moisture is important, especially during dry periods and blooming. Gladiolus generally require about 1 inch of water per week, applied deeply. Watering in the early morning is beneficial, allowing moisture to reach the roots before rapid evaporation. Applying a 2 to 4-inch layer of organic mulch around the base helps retain soil moisture and suppress weed growth.
Gladioli benefit from regular feeding. A balanced fertilizer, such as a 5-10-10 or 10-10-10 formulation, can be applied at planting time. Additional feeding can occur when shoots are about 6 to 10 inches tall and again when flower buds begin to form. Tall gladiolus varieties often require staking to prevent their heavy flower spikes from bending or falling over. Insert stakes early in the growing season, before plants become too tall, to avoid damaging corms or roots.
Regular inspection helps identify issues like thrips or aphids, which can cause discoloration or stunted growth. Good cultural practices, including cleaning plant debris and ensuring adequate spacing, reduce the risk of common fungal diseases like corm rot or leaf spot. Deadheading, or removing spent flowers, improves the plant’s appearance and prevents seed formation, though it does not typically encourage more blooms. Leave foliage intact after flowering; leaves photosynthesize and store energy in the corm for the next year’s growth.
Winter Care and Corm Storage
In colder climates, where ‘Black Surprise’ gladiolus are not hardy (USDA Zones 7 and below), corms must be lifted and stored for winter. Lift corms in late summer or early fall, four to six weeks after blooming, or after the first hard frost causes foliage to die back. Dig up the entire plant using a spade or garden fork.
Shake off excess soil from the corms. Cut stalks down to about 1 to 2 inches above the corm. Cure corms in a warm, dry, well-ventilated area, out of direct sunlight, for two to three weeks. Curing dries corms thoroughly, preventing rot. Once cured, remove any remaining soil, discard old mother corms, and separate cormlets if desired. Store healthy, dry corms in a cool, dark, and dry location, with temperatures ideally between 35 and 50°F (2-10°C). Mesh bags, old nylon stockings, or slatted boxes with newspaper between layers provide good air circulation.