[7] The column is elongated when expanded; it has a fairly small pedal disc and is thicker at the distal (upper) end.

The first and third whorls of tentacles are endocoelic (set between the mesenteries in the column interior) and the second and fourth are attached marginally.

The sea anemone is well-armed with cnidocytes which are of varying lengths, the ones in the central region of the tentacles being least variable.

[8] Breeding in Actinodendron arboreum takes place when gametes are shed into the body cavity and passed out into the water column.

After fertilisation, the planula larva forms part of the plankton before settling on the seabed, undergoing metamorphosis and developing into a juvenile sea anemone.