Dahlias are half hardy, so keep them protected from frost. Pot tubers individually between February and April and grow them on in a greenhouse or bright indoor position. Alternatively, start them outside in May, once the risk of frost has passed.
Out of season
Deluxe
Lovers of deep, dark, velvety blooms will simply not be able to resist the dramatic Dahlia 'Black Jack'. One of the darkest, near-black Dahlia varieties available, 'Black Jack's sensational colour is intensified by the striking cactus dahlia shape – with a wealth of spiky petals radiating out from its almost-black heart. And if the flowerheads weren’t eye catching enough, this variety features a really unusual foliage colour, rarely seen on a dahlia – dark green leaves are contrasted by deep red veining and stem!
The buds, too, are large and sculptural – so with its statuesque height, Dahlia 'Black Jack' is hard to beat for providing architectural interest in your garden. Grow it alongside silvery foliage in a stylish, contemporary scheme, or contrast with brighter colours to add real depth to your summer display.
Quantity
Plant profile
Plant calendar
For planting out later, use a snug-fitting 15–20cm pot filled with peat-free multipurpose compost. For a patio display, plant directly into a container at least 30cm wide and keep it somewhere bright and frost free until it can move outdoors.
Position the old stem facing upwards, with the tubers covered and the stem stump level with the compost. Tubers naturally vary in size and shape and may arrive without visible buds. Bent necks are usually fine if they remain firmly attached, so do not remove them.
Water after planting, then allow the compost to become almost dry before watering again while the tuber remains dormant. Once shoots and leaves are growing strongly, water more regularly, always allowing excess water to drain away.
Plant out after the last frost, once the plant is around 20–30cm tall and its roots hold the compost together. Space dahlias approximately 30–50cm apart in borders, allowing less room for compact varieties. Water thoroughly after planting.
Water regularly during active growth and deadhead or cut flowers often. Dahlias usually bloom from July or August until the first frost, although later-planted tubers may start in late August or September. In autumn, lift, clean and dry the tubers, then store them somewhere cool, dry, airy and frost free.
- Botanical name
- Dahlia 'Black Jack'
- Flower colour
- Near-black, red
- Tuber size
- 1
- Established height
- 1.2-1.5m
- Established spread
- 50-70cm
- Growing skill
- Easy to grow
- Habit
- Upright
- Hardiness
- Half hardy
- Leaf colour
- Bronze, green
- Mouse resistant
- No
- Plant spacing
- 5 tubers per m2
- Pollinator friendly
- No
- Position
- Sheltered
- Rabbit resistant
- No
- Scented
- No
- Soil acidity
- Any
- Soil moisture
- Free draining
- Soil type
-
Loam
Sandy
Multipurpose compost
Loam-based compost - Suitable for
-
Large containers
Borders
Gravel gardens
Coastal gardens
Cottage gardens
Low maintenance gardens
Cut flower gardens - Sunlight
-
Full sun
Partial shade - Toxicity
- No report
- Years to establish
- 1st year
Good for cutting
Thrives in full sun
Perennial
Packed in paper
Low maintenance
Top-size tubers
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Dahlia 'Black Jack' reviews
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