Dahlia Manhatten Island

Dahlia ‘Manhattan Island’ is a real showstopper, loved for its bold, glamorous blooms that bring instant drama to the summer border. It’s best known for its striking colour mix—often hot pinks, magentas and red tones with lighter highlights—creating a vibrant, “party in a flower” look that stands out from across the garden. Flowering freely from midsummer right up until the first frosts, it’s perfect for keeping colour going when so many other plants are starting to fade.

It also makes an excellent cut flower, with strong stems and eye-catching blooms that add serious impact to arrangements. Plant it in a sunny spot, keep it watered and fed, and you’ll be rewarded with months of bold, beautiful flowers.

Planting Instructions

When to Plant:

Plant Dahlia tubers in spring. For the earliest flowers, start tubers in pots indoors from March to April, then plant out once the risk of frost has passed. If planting directly outside, wait until late spring when the soil has warmed.

Where to Plant:
Choose a sunny, sheltered position with fertile, well-drained soil. Dahlias are ideal for mixed borders, cutting gardens and patio containers. They love warmth and perform best in full sun.

How to Plant:

• Depth: Plant tubers about 10–15 cm (4–6 inches) deep, with the old stem (or growing point) facing upwards.
• Spacing: Space plants 45–60 cm (18–24 inches) apart, depending on the final size.
• Soil Prep: Enrich the planting area with well-rotted compost or manure. In heavy soil, improve drainage with grit.

Watering:
Water after planting. Once shoots appear and growth is underway, keep soil evenly moist, especially in dry spells. Avoid waterlogging. Container-grown Dahlias may need watering daily in hot weather.

Aftercare Tips:

• Pinch out the growing tip once plants are around 30 cm tall to encourage bushier growth and more flowers.
• Stake taller stems if needed, especially in exposed borders.
• Deadhead regularly (or cut for the vase) to keep plants flowering until autumn.
• After the first frost blackens the foliage, lift tubers and store dry and frost-free over winter, or protect in the ground with a thick mulch in milder areas.

Top Tip:
If you want maximum impact, plant Dahlia ‘Manhattan Island’ with contrasting colours like lime-green foliage or deep purple Salvias—the vibrant blooms will pop even more.

Plant Details

Flowering Period:
July - October (until first frosts)

Height:
36–48" (90–120cm) (approx. depending on conditions)

Position:
Full sun

Tender Perennial:
Overwinter tubers frost-free in the UK