Dahlia Mystery Day

Dahlia ‘Mystery Day’ is a dahlia with real theatre—bold, dramatic and impossible to ignore. It produces richly coloured blooms in deep velvety red with striking crisp white tips, creating a high-contrast look that pops from across the garden and looks fantastic in bouquets. The flowers are generously sized and produced freely from midsummer right through to the first frosts, so you get months of colour when the border is in full swing.

This variety is ideal for sunny borders and patio pots, and it’s a brilliant cut flower too. The more you deadhead (or pick for the vase), the more blooms you’ll get—so ‘Mystery Day’ really earns its keep.

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:
For maximum impact, let Dahlia ‘Mystery Day’ shine against simple companions—dark foliage, grasses or deep purple Salvias will make those red blooms and white tips look even more dramatic.

Plant Details

Flowering Period:

July - October (until first frosts)

Height:
30–40" (75–100cm) (approx. depending on conditions)

Position:
Full sun

Tender Perennial:
Overwinter tubers frost-free in the UK