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Herbaceous Perennial

Iris chrysographes 'Black Knight'

iris 'Black Knight'

A highly attractive, clump-forming, rhizomatous perennial with upright, strap-like, green leaves and erect stems in summer bearing dark-purple-black flowers with a golden-yellow streak on the lower petals, known as falls

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Ultimate height

0.1–0.5 metres

Time to ultimate height

2–5 years

Ultimate spread

0.1–0.5 metres

Loam

Moisture

Moist but well–drained, Well–drained

pH

Neutral, Acid

	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Full sun
Partial shade

Aspect

West–facing or South–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)

Botanical details

Family: Iridaceae
Native to GB / Ireland: No
Foliage: Deciduous
Habit: Clump forming, Columnar upright
Potentially harmful: Harmful if 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: Iris may be rhizomatous or bulbous perennials, with narrow leaves and erect stems bearing flowers with 3 large spreading or pendent fall petals, alternating with 3 erect, often smaller, standard petals, in late winter, spring or early summer
Name status: Not established

How to grow

Cultivation

Grow in well-drained, neutral to slightly acid loam in full sun or partial shade. Mulch in spring

Propagation

Propagate by division of the rhizome shortly from mid-summer to early autumn. See dividing irises

Suggested planting locations and garden types

City and courtyard gardens
Coastal
Cottage and informal garden
Patio and container plants
Cut flowers
Flower borders and beds
Garden edging
Wall side borders

Pruning

Cut back old flower stems after flowering and remove dying foliage in autumn

Pests

May be susceptible to slugs and snails

Diseases

May be susceptible to aphid-borne viruses, bacterial soft rot and grey moulds; see Iris diseases

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