Gladiolus ‘Blue Isle’ is a popular variety known for its unique and captivating blue-purple coloration. Its dramatic presence adds a distinctive appeal to gardens and makes it highly suitable for cut flower displays.
Characteristics of Gladiolus Blue Isle
Gladiolus ‘Blue Isle’ features dramatic, deep blue-purple flowers that can reach heights of up to four feet. Individual florets are typically 3 to 4 inches wide, arranged along one side of robust stems, with 10 to 12 flowers often open simultaneously. This striking appearance makes it a focal point in any garden. This variety generally blooms from mid to late summer, approximately 70 days after planting. Its sword-like foliage provides a strong visual base, and its long-lasting color makes it excellent for cut flower arrangements.
Planting Gladiolus Blue Isle
Plant ‘Gladiolus Blue Isle’ corms in spring, after the last frost and when soil temperature reaches at least 55°F (13°C). Choose a site with full sun, receiving 6 to 8 hours of direct sunlight daily, for robust growth and vibrant blooms. Well-drained, organically rich, moist soil with a pH of 6.0-7.0 is preferred. Amending heavy clay soils with compost can improve drainage.
Plant corms 4 to 6 inches deep, pointed end up, and spaced approximately 6 inches apart. For continuous summer blooms, stagger planting every 10 to 14 days until midsummer. Planting in groups of 7 or more creates a more impactful visual effect. Water thoroughly after planting to settle the soil.
Care and Maintenance
Consistent watering is important, especially during dry periods, aiming for about 1 inch of water per week. Avoid overwatering, as soggy conditions can lead to corm rot. Apply organic mulch around the plant’s base to retain soil moisture, regulate temperature, and suppress weeds. Full sun exposure is important throughout the growing season for optimal flowering.
Apply a balanced fertilizer (e.g., 5-10-10 or 10-10-10 NPK) when shoots are about 6 inches tall and again when flower spikes begin to form, or every 3-4 weeks. Staking is often necessary for tall flower spikes to prevent bending, especially in windy conditions; insert supports early to avoid damaging roots. Deadhead spent flower spikes to encourage stronger corm development for the next season.
Winter Care and Storage
In colder climates (USDA Hardiness Zones 3-7), lift ‘Gladiolus Blue Isle’ corms before the first hard frost. The ideal time is after foliage has faded and yellowed, but before the ground freezes. Carefully dig up the plant, shake off loose soil, and cut the stalk to 1 to 2 inches above the corm, avoiding bruising.
Cure corms in a warm, dry, well-ventilated location, out of direct sunlight, for two to three weeks. This allows them to dry completely and develop a protective skin, reducing storage rot. After curing, remove any remaining soil, old corms, and separate small cormels. Store cleaned corms in breathable containers (e.g., paper, cloth, or mesh bags) in a cool, dark, frost-free location, ideally around 35° to 45°F (2° to 7°C).
Common Issues and Solutions
Common issues for gladiolus growers include pests and diseases.
Pests
Thrips: These tiny insects suck sap from leaves and flowers, causing discoloration and deformities like silver streaks or brown edges. They can also attack corms in storage, leading to sticky, shriveled corms. Control with neem oil, insecticidal soaps, or by treating infested corms with hot water at 46°C for six weeks.
Aphids: These pests cluster on leaves and flower buds, feeding on plant sap and causing curled leaves and stunted growth. Dislodge them with a strong water spray or introduce natural predators like ladybugs.
Diseases
Corm Rot: Often caused by fungi (e.g., Fusarium, Penicillium), this leads to soft or mushy corms and stunted growth. It results from poor drainage or improper storage. Ensure well-drained soil and proper curing before storage to prevent rot.
Non-Blooming
Insufficient Sunlight: Gladiolus require 6-8 hours of direct sun daily to flower effectively.
Poor Corm Quality: Undersized or diseased corms can prevent blooming.
Nutrient Deficiencies: Lack of phosphorus can lead to poor flowering; apply a balanced fertilizer.
Distorted Flowers: May indicate thrips infestation or viral diseases, causing streaking and deformation.