Helianthus annuus 'Florenza'

RHS Plant Profile
sunflower 'Florenza'

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Annual Biennial

A branching annual to a height of around 110cm with green leaves. Rusty maroon-red flowers with yellow tips and dark chocolate-brown centres appear throughout the summer. A great choice for borders and for cutting

Position

Full sun

Soil Types

Chalk, Clay, Loam

Max Height

1-1.5 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity
1 year
Max Spread
0.1-0.5 metres
Max Height
1-1.5 metres

Growing Conditions

Chalk Clay Loam
Moisture
Moist but well–drained
pH
Acid or Alkaline or Neutral

Position

Full sun
Aspect
East–facing or South–facing or West–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)
H2

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Asteraceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Bushy, Clump forming
Genus
Helianthus can be tall, erect annuals, tuberous or rhizomatous perennials, with coarse simple leaves and large daisy-like flower-heads
Name Status
Unresolved

How to Grow

Cultivation

Grow in moderately fertile, neutral to alkaline, humus-rich, moist but well-drained soil in full sun. This plant was included in the RHS Helianthus (sunflower) trial 2024 https://www.rhs.org.uk/plants/trials-awards/plant-trial-results/fleuroselect-sunflowers

Propagation

Propagate by seed (sown indoors) between April and May and keep in a sunny location, planting out in late spring or early summer when the risk of frost has passed. Also propagate by seed (sown outdoors) when the risk of frost has passed

Suggested planting locations and garden types

  • City and courtyard gardens
  • Cottage and informal garden
  • Patio and container plants
  • Wildlife gardens
  • Flower borders and beds

Pruning

Cut back after flowering or leave flower heads for birds to eat seed

Pests

May be susceptible to slugs and snails

Diseases

May be susceptible to powdery mildews and sclerotinia diseases