Ultraviolet Dahlia Bulbs

The white is underneath, not on top. Each petal is magenta-violet on the face and white at the base, so as the flower opens, the accumulated white at the center reads as a glow rather than a marking. It’s a large-flowered decorative type, fully double, and the color intensity holds right through to the last petal.

What you get

• Graded tubers with a visible eye, packed in peat.
• Blooms 6–8 in across — a dinnerplate-adjacent size, one flower per stem.
• Plants 36–44 in tall. Heavy heads on tall stems: stake at planting.

An honest note

Large double dahlias are slow to open and easily spoiled by rain, which balls the petals and turns them brown. In a wet climate, grow this one where it gets morning sun to dry the flower quickly, or accept that some blooms will be lost.

How to plant

• Soil temperature matters more than the calendar. Wait until it holds 60°F / 15°C at 4 in deep — normally about two weeks after your last frost.
• Lay the tuber flat, eye up, 4–6 in under the surface, and leave 15–18 in between plants for airflow.
• No water until shoots appear. A dormant tuber in wet soil rots in about ten days; roots don’t form until the shoot breaks through.
• Six hours of sun minimum, and a stake in at planting time if the variety runs tall. Driving one in later spears the tuber.

Hardiness & season

• Perennial in USDA zones 8–11, grown as an annual or lifted and stored over winter in zones 3–7.
• First flowers 8–10 weeks after planting, then continuous bloom until the first hard freeze.
• Pinch out the growing tip at 12 in for a bushier plant with more, smaller stems — skip it if you want a few large blooms.
• Keep cutting and deadheading. A dahlia allowed to set seed stops producing buds, and the September flush never happens.