Thalia dealbata (Hardy Water Canna) - Tall Architectural Leaves & Purple Spikes for Deep Shelves (Peat-Free, Pesticide-Free; Non-Native)

A striking North American wetland plant for larger wildlife ponds. Blue-green, paddle-shaped leaves rise on waxy stems, topped in summer with airy purple flower spikes that draw the eye and offer nectar to bees and hoverflies. The bold stems make excellent dragonfly/damselfly perches and throw welcome dappled shade over the shallows for amphibians and invertebrates. Rhizomatous, upright clumps to 1.2-2 m when happy.
Native status: Non-native; garden-safe and non-invasive in the UK when managed.

Where it thrives

Light: Full sun (tolerates light/partial shade)
Moisture/Zone: Deep marginal shelf with 30-60 cm water over the crown (can go a little deeper once established); still or slow water; avoid fountain splash
Pond size: Best for medium to large ponds (needs space above and below water)
Substrate: Mineral subsoil/loam topped with washed gravel - never peat

Planting & care

• Plant rhizomes on a stable deep shelf directly into the pond’s mineral soil (Joel-style) or in a large nursery basket if you need containment.

• Keep consistently wet and sunny for strong growth.

• Hardiness: Generally hardy in much of the UK if the crown stays below ice; in very cold regions, site deeper, mulch the crown, or overwinter a divided piece in a frost-free place.

• Remove old leaves/stems in late winter; divide sparingly in late spring as water warms.

• Always peat-free & pesticide-free.

Safety (important & honest):
Ornamental use only - do not ingest. Low risk, but sap can irritate sensitive skin; wear gloves. Keep plant material and soil out of natural watercourses.

Truth-first wildlife note:
A big, architectural plant that needs depth, sun and summer warmth. NOT suited to small barrels or exposed, windswept sites (large leaves can tear). If your pond is shallow or tiny, choose structural natives like Flowering Rush or Greater Spearwort instead.

Joel says…
“Give Thalia a sunny, deep shelf and it’ll stand like living sculpture. I keep it out of fountain splash and leave the tall stems for dragonflies to patrol.”