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AquaticHerbaceous PerennialConservatory Greenhouse

Thalia dealbata

powdery alligator-flag

An evergreen, marginal aquatic perennial forming a clump of long-stalked, erect, narrowly ovate leaves to 40cm in length, covered with white powder, and slender stems bearing panicles of purple flowers 2cm across. Although not carnivorous as such, this plant may trap and kill small insects such as hoverflies and small bees during the pollination process.

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Size
Ultimate height
1.5–2.5 metres
Time to ultimate height
5–10 years
Ultimate spread
0.5–1 metres
Growing conditions
Loam
Moisture
Poorly–drained
pH
Acid, Alkaline, Neutral
Colour & scent
StemFlowerFoliageFruit
Spring Green Grey Silver
Summer Purple Green Grey Silver
Autumn Green Grey Silver
Winter Green Grey Silver
Position
  • Full sun
Aspect

South–facing or West–facing or East–facing

Exposure
Sheltered
Hardiness
H2
Botanical details
Family
Marantaceae
Native to the UK
No
Foliage
Evergreen
Habit
Clump forming
Genus

Thalia can be evergreen or deciduous perennials with long-stalked, lance-shaped leaves and long stems bearing violet-purple flowers in panicles

Name status

Correct

Plant range
S US, Mexico

How to grow

Cultivation

Under glass, grow in baskets of loam based compost in full light. Grow as a marginal aquatic in a planting basket of fertile, loamy, humus-rich soil in up to 15cm of water at the edge of a sunny pool. In colder areas it will become deciduous. See pond plants for further advice

Propagation

Propagate by seed sown at 16-21°C, in moist seed compost, when ripe or in spring. Propagate by division in spring

Suggested planting locations and garden types
  • Sub-tropical
Pruning

Remove old flowers and leaves regularly

Pests

Generally pest-free

Diseases

Generally disease-free

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