The Grand Prix Dahlia is a striking addition to any garden, known for its substantial and visually captivating blooms. Its impressive size and vibrant presence make it a popular choice, creating a focal point and enhancing outdoor spaces.
Grand Prix Dahlia Characteristics
The Grand Prix Dahlia features large, fully double blooms, 8 to 10 inches across. These flowers display bright yellow petals with distinct white tips, creating a striking two-tone effect. Classified as a dinnerplate dahlia, this variety reaches a height of 36 to 48 inches. Grand Prix Dahlias bloom from July until the first frost.
Planting Grand Prix Dahlias
Planting Grand Prix Dahlias begins with selecting an appropriate site. These plants thrive in full sun, requiring at least 6 to 8 hours of direct sunlight daily. Choose a location sheltered from strong winds, as large blooms can become top-heavy. Well-drained, fertile soil with a slightly acidic to neutral pH (6.0-7.0) is necessary. Amend the soil with compost or well-rotted manure to improve aeration and fertility.
Planting should occur in spring after the last frost, when soil temperature reaches 60°F (15°C). Plant tubers 3 to 6 inches deep, with the “eye” facing upwards. Space tubers 24 to 36 inches apart. After planting, avoid immediate heavy watering; wait until green shoots emerge to prevent tuber rot.
Ongoing Care for Grand Prix Dahlias
Grand Prix Dahlias require consistent moisture once they begin to grow. Water deeply 2 to 3 times per week, increasing frequency during hot or dry periods. Avoid overwatering, as soggy soil can lead to tuber rot. Container plants may need daily watering due to quicker soil drying.
Fertilization promotes abundant flowering. Use a fertilizer with lower nitrogen and higher phosphorus and potassium, such as a 5-10-10 ratio. High nitrogen fertilizers promote leafy growth at the expense of blooms. Apply fertilizer every 2 to 3 weeks for container plants and every 3 to 4 weeks for in-ground plants, starting about 30 days after planting.
Grand Prix Dahlias require staking or support to prevent stems from flopping and protect heavy flowers. Install stakes, such as sturdy wooden or metal poles, or use caging systems early in the growing season, shortly after planting, to avoid damaging tubers. As the plant grows, tie stems to the support, leaving some slack for movement.
Deadheading, the removal of spent flowers, encourages continuous blooming by redirecting the plant’s energy to new flower development. Inspect plants regularly and snip off faded blooms at the stem. Pinching back the main shoot when the plant is about 10 to 12 inches tall encourages bushier growth and more flowers.
Regular inspection helps manage common pests like aphids, slugs, and snails. Good air circulation and avoiding overhead watering minimize disease issues such as powdery mildew. Address pest and disease problems promptly to maintain plant health.
Overwintering Grand Prix Dahlias
In colder climates (USDA Zones 3-7), Grand Prix Dahlia tubers need to be dug up and stored for winter. Wait until after the first hard frost causes foliage to turn brown, which stimulates tubers to set eyes for the following season. After cutting back foliage, carefully dig around tuber clumps, avoiding damage.
Once dug, gently wash excess dirt from tubers with water, taking care not to puncture their skin. Allow cleaned tubers to dry for several days to a week in a cool, dry, dark location with good air circulation. This curing process prevents rot during storage.
Store dried tubers in a cool, dark, frost-free environment, between 40°F and 50°F. Containers such as milk crates, plastic bins, paper bags, or cardboard boxes work. Pack them in slightly moist peat moss, vermiculite, or sand for insulation and to maintain moisture, preventing shriveling or rotting. Periodically check tubers throughout winter, removing any showing signs of mold or rot.