Gladiolus 'Black Jack' (L) | sword lily 'Black Jack'

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Bulbs

A large-flowered gladiolus, to around 100cm high, with green sword like leaves. Tall flower spikes produce large crimson-red, velvety flowers with an edge of deeper dark almost black bordering the bloom, dramatic blooms for the summer

Position

Full sun

Soil Types

Chalk, Loam, Sand

Max Height

0.5-1 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity: 2–5 years
Max Spread: 0.1-0.5 metres
Max Height: 0.5-1 metres

Growing Conditions

Chalk Loam Sand

Moisture: Well–drained or Moist but well–drained
pH: Acid or Alkaline or Neutral

Position

Full sun

Aspect: South–facing or West–facing or East–facing
Exposure: Sheltered
Hardiness

Hardiness Ratings

All ratings refer to the UK growing conditions unless otherwise stated. Minimum temperature ranges (in degrees C) are shown in brackets

H1A: under glass all year (>15C)
H1B: can be grown outside in the summer (10 - 15)
H1C: can be grown outside in the summer (5 - 10)
H2: tolerant of low temperatures, but not surviving being frozen (1 to 5)
H3: hardy in coastal and relatively mild parts of the UK (-5 to 1)
H4: hardy through most of the UK (-10 to -5)
H5: hardy in most places throughout the UK even in severe winters (-15 to -10)
H6: hardy in all of UK and northern Europe (-20 to -15)
H7: hardy in the severest European continental climates (< -20): H3

Colour & Scent

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Iridaceae
Native to GB/Ireland: No
Foliage: Deciduous
Habit: Columnar upright
Potentially harmful: Ornamental bulbsnot to be eaten. Wear gloves and other protective equipment when handling. Pets: Harmful if eaten. For further information and contact numbers regarding pets, see the HTA guide to potentially harmful plants
Genus: Gladiolus are cormous perennials with fans of sword-shaped or linear leaves and spikes of funnel-shaped flowers
Name Status: Accepted
Horticultural Group

Horticultural Classification Codes

Horticultural Classification Codes are often given to genera which have a large number of species or cultivars. They are used to categorise cultivated plants based on specific, shared characteristics such as shape, colour, size or flowering time, and can be displayed as letters or numbers

For example:
Dahlia ‘Sunset Kate (Sin) = Single flower
Rosa ‘Marigold’ (HT) = Hybrid Tea: Large-flowered Grandiflorus Group gladioli have flowers 11-14cm across in summer

How to Grow

Cultivation

Grow in fertile, well-drained soil in full sun, planting the corms 15cm deep in spring, on a bed of sharp sand to aid drainage; in frost-prone areas, lift when the leaves turn yellow-brown, and store the new corms in a dry, frost-free place until the following spring; in milder areas, add a thick dry mulch over winter This plant was included in the RHS Gladiolus (gladioli) trial 2024-2025 https://www.rhs.org.uk/plants/trials-awards/ongoing-plant-trials/gladiolus

Propagation

Propagate by division, separating cormlets when dormant

Suggested planting locations and garden types

City and courtyard gardens
Cottage and informal garden
Flower borders and beds
Wall side borders
Cut flowers

Pruning

No pruning required, flowers may need staking with a cane. See staking: perennials

Pests

May be susceptible to gladiolus thrip, aphids and slugs

Diseases

May be susceptible to gladiolus corm rot, grey moulds (Botrytis), Fusarium bulb rot, gladiolus core rot, gladiolus dry rot, gladiolus scab and neck rot, fungal leaf spot, and virus diseases