Pistia stratiotes

RHS Plant Profile
water lettuce

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water lettuce visionspictures.com

Other common names

shell flower, tropical duckweed

Aquatic
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This plant is listed as an invasive non-native species in the UK – see Cultivation section for details A tender aquatic perennial with soft, light green, ridged leaves forming floating rosettes, and long, feathery roots hanging beneath

Position

Full sun

Max Height

0.1-0.5 metres

Max Spread

0.1-0.5 metres

Size

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

Position

Full sun
Aspect
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)
H1B

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Araceae
Native to GB/Ireland
No
Foliage
Evergreen
Habit
Floating
Potentially harmful
Harmful if eatenskin/eye irritant. Wear gloves and other protective equipment when handling
Genus
A genus of just one species of aquatic plant present in most tropical and sub-tropical fresh waterways due to both natural and human introduction. It is considered invasive and also offers a breeding ground for mosquitos. The rosettes of leaves are thick, soft and hairy and flowers pink-purple
Name Status
Correct
Plant Range
Tropics

How to Grow

Cultivation

This plant is listed on Schedule 9 of the Wildlife & Countryside Act (1981), the Wildlife (Northern Ireland) Order 1985 and the EU list of Invasive Alien Species of Union Concern (applies in NI) as an invasive non-native species. It should not be planted or caused to grow in the wild in the UK. It is also banned from sale in Northern Ireland. See RHS advice on invasive non-native species for further information

Propagation

See cultivation notes

Pests

See cultivation notes

Diseases

See cultivation notes