Dahlia Cactus “Spider” varieties (popularly known as Hollyhill Spider Woman) are striking summer-blooming perennials famous for their slender, curled, and spiky petals. While they are sold as “bulbs,” they actually grow from tuberous roots. [1, 2, 3, 4]
These spiky blooms thrive in full sun and fertile, well-draining soil. Here are the key actionable steps for growing them: [1]
- Planting: Plant the tubers in the spring after the soil has warmed to at least 15°C (60°F). Place them 10 to 15 cm (4 to 6 inches) deep on their sides, with the “eye” (sprout) facing upward. [1, 2]
- Watering & Feeding: Do not water immediately after planting to prevent rot; wait until green shoots emerge. Once actively growing, provide deep waterings (about 2.5 cm/1 inch per week). Use a balanced, phosphorus-heavy fertilizer monthly to promote vibrant blooming. [1, 2, 3]
- Maintenance: Pinch off the central growing tip when the plant is 30 cm (12 inches) tall to encourage bushy growth. Deadhead spent blooms regularly to keep the plant flowering from July through October. [1, 2, 3]
- Winter Care: These plants are not frost-hardy (USDA zones 8-10). In regions with freezing winters, carefully dig up the tubers in the fall after the first frost, dry them, and store them in a cool, dark, and frost-free place (like a cardboard box with peat moss or sand) until spring. [1, 2, 3]
