Hemerocallis 'Cosmic Blast'

RHS Plant Profile

daylily 'Cosmic Blast'

RHS / Joanna Kossak

Herbaceous Perennial

A clump-forming perennial with grassy, arching leaves. Greenish-yellow flowers up to 17cm across, with striking purple markings, are produced in mid- to late summer

Position

Full sun

Soil Types

Chalk, Clay, 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 Clay Loam Sand

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

Position

Full sun

Aspect: South–facing or West–facing
Exposure: Exposed or 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): H6

Colour & Scent

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Asphodelaceae
Native to GB/Ireland: No
Foliage: Semi evergreen
Habit: Bushy
Potentially harmful: TOXIC to pets (cats) - see the HTA guide to potentially harmful plants for further information and useful contact numbers
Genus: Hemerocallis may be evergreen or herbaceous perennials, with narrow, strap-shaped leaves and funnel-shaped flowers on erect stems in late spring or early summer
Name Status: Accepted

How to Grow

Cultivation

Grow in fertile, moist but well-drained soil preferably in full sun. Flowering is likely to be poor in shadier situations. Tolerant of heavy clay and poorer soils. May need watering in spring to early summer in dry conditions to ensure flowering. See Hemerocallis cultivation for details

Propagation

Propagate by division in spring or autumn

Suggested planting locations and garden types

City and courtyard gardens
Cottage and informal garden
Prairie planting
Coastal
Flower borders and beds

Pruning

Deadheading will improve appearance, and can help reduce hemerocallis gall midge. Cut back flower stems after flowering has finished. Remove dead foliage as required

Pests

May be susceptible to aphids, slugs, snails, hemerocallis gall midge, slugs, glasshouse red spider mite and thrips

Diseases

May be susceptible to fungal leaf spot, rust diseases and bacterial leaf and stem rot