‘Marble Ball’ Dahlia (Dahlia × hortensis) forms an upright branching clump approximately 70 cm tall and 50 cm wide. Fully double, spherical, orderly flowers measure about 9 cm; their light purple petals carry purple or white stripes, spots, and splashes that make every flowerhead different. Dark green divided foliage emphasizes this lively mosaic. From midsummer until the first frost, Van Noort’s No. 1 tuber produces sturdy stems suited to borders, large containers, and arrangements. The Ball classification accurately describes its compact, regular, geometric outline. RHS records confirm the accepted cultivar, flower dimensions, distinctive pattern, and clump-forming habit.

Plant the tuber in spring after the final frost when soil has warmed and drained. Lay it 10 cm deep with its bud facing upward in fertile, humus-rich soil that remains moist yet drains freely. Leave approximately 50 cm around the crown and install discreet support at planting. Water sparingly before emergence, then deeply at soil level whenever the surface begins to dry. Pinch the young shoot between 20 and 30 cm to encourage several branches. Incorporate mature compost, then apply moderate fertilizer richer in potassium once buds appear. Avoid standing water, excessive nitrogen, and irrigation over the flowerheads. Maintain open airflow during humid weather.

Place Marble Ball beside a path where the unique pattern of every flower can be examined. Purple and white tones combine with white gauras, blue salvias, purple verbenas, silver artemisias, and bronze grasses. Harvest stems early in the morning when flowerheads are fully open, then remove faded flowers regularly to renew buds. Highly double blooms provide little accessible pollen, so include nearby simple flowers for pollinators. Watch for slugs, aphids, earwigs, and spider mites while maintaining generous airflow. In cold Canadian climates, lift the tuber after the first frost, dry its surface, label it, and store it somewhere cool, dry, dark, and frost-free until spring.