Very invasive native with strong, tall, flat, leaves and unusual spiky flower heads. The flowers are borne in spherical heads looking a bit like green conkers.
Top tip: Can be invasive and bit of a thug with roots strong enough to puncture a liner. Excellent for reed beds.
Flowers: June-August followed by spiky fruits.
Propagation: Very easy to divide.
Depth of water over the soil: 10-30cm.
Planting: Plant into 5lt planting crate using heavy garden loam or Westland Aquatic Soil