Alexandra palm

Archontophoenix alexandrae
infestation of young trees along a creek in Keperra in Brisbane (Photo: Sheldon Navie)
sapling growing in a waterway at Redbank in Ipswich (Photo: Sheldon Navie)
habit of mature tree in fruit (Photo: Sheldon Navie)
expanded base of trunk (Photo: Sheldon Navie)
close-up of grey bark on mature tree, showing leaf scars (Photo: Sheldon Navie)
massive leaves with numerous narrow leaflets (Photo: Sheldon Navie)
the thick leaf stalks (Photo: Sheldon Navie)
whitish undersides of the leaflets (Photo: Sheldon Navie)
large, much-branched, flower cluster (Photo: Sheldon Navie)
fruiting clusters from below, showing their thick branches (Photo: Sheldon Navie)
immature fruit on whitish branches (Photo: Sheldon Navie)
seedlings (Photo: Sheldon Navie)
Tree
Whorled
Simple
Cream
Green
Discoloured

A tall palm with a single trunk growing up to 30 m in height. Its grey trunk (up to 30 cm thick) is ringed with noticeable leaf scars and is usually expanded at the base. Its massive leaves (3.5-4.5 m long) are clustered at the top of the trunk and have 60-80 narrow leaflets on each side. The base of the leaf stalk forms a bright green or light green sheath-like structure around the trunk (up to 1 m long). Its leaflets (up to 80 cm long and 3-5 cm wide) have dark green upper surfaces and whitish-green or silvery-grey undersides.Its large flower clusters and have numerous branches and are mostly white or cream in colour. Its somewhat rounded fruit (8-14 mm long) turn from green to bright red as they mature.

Common names 
Also known as: Alexandra palm, Alex palm, Alexander palm, feather palm, king palm, northern bangalow palm,
Family 
Arecaceae
Deciduous 
No
Flowering time 
Spring - Summer
Native/Exotic 
Native
Origin 
Native to northern and central Queensland (i.e. from Baffle Creek, just south of Gladstone, to Bathurst Bay on the Cape York Peninsula).
Notifiable 
No
Council declaration 
SIL – Special Investigation List
Known distribution 

This species is becoming naturalised in the Moreton district in south-eastern Queensland. It is possibly also becoming naturalised in the coastal districts of northern New South Wales.

Habitat 

In its native habitat, in northern Queensland, this species is generally confined to lowland swamps, drainage lines and riparian rainforest vegetation. It is an emerging weed of waterways and riparian vegetation in the wetter coastal districts of south-eastern Queensland.

Habit 

A tall palm with a single trunk growing up to 30 m in height and with a crown that usually contains about 10-12 leaves.

Impact and control methods 

Potential weed of riparian zones in SEQ.

Stem and leaves 

The grey trunk is ringed with noticeable leaf scars, but is otherwise smooth. This trunk is up to 30 cm thick, but is frequently expanded at the base (up to 50-60 cm across). The massive leaves (3.5-4.5 m long on mature trees) are alternately arranged, but are clustered at the top of the trunk. These leaves are usually not held flat, but instead are twisted laterally. Each of the leaves is borne on a thick stalk (i.e. petiole) up to 40 cm long and has 60-80 long and narrow leaflets (i.e. linear pinnae) on each side. The base of the leaf stalk forms a sheath-like structure around the trunk (i.e. crownshaft) that is up to 1 m long and bright green or light green in colour. The leaflets (up to 80 cm long and 3-5 cm wide) have dark green upper surfaces and paler whitish-green or silvery-grey undersides. They have entire margins and pointed tips (i.e. acuminate apices) and are all borne in the same plane.

Flowers and fruits 

The flower clusters (i.e. inflorescences) are produced just below the sheath-like leaf stalk bases (i.e. crownshaft). Young flower clusters are enclosed three large bracts (up to 80 cm long and 12 cm wide). These clusters (50-100 cm long and up to 50 cm wide) are borne on stalks (i.e. peduncles) up to 15 cm long and have numerous upright (i.e. erect) to drooping (i.e. pendulous) branches. The flowering branches and flowers are mostly white or cream in colour. Separate male and female flowers are present in these clusters. The stalkless (i.e. sessile) flowers are borne in threes (i.e. triads) along the flowering branches, each group having a single female (i.e. pistillate) flower and two male (i.e. staminate) flowers. The male flowers (6-9.5 mm long) have three small sepals (about 2 mm long) and three larger petals (6-7 mm long and 2-2.5 mm wide). They also have 9-16 stamens, each consisting of a short stalk (i.e. filament) about 2 mm long topped with a yellow anther (3.5-4 mm long). The smaller female flowers (about 4 mm long) have three tiny sepals, three petals, and an ovary topped with a short style and three stigmas. The round or egg-shaped (i.e. ovoid) fruit (8-14 mm long and 6-11 mm wide) turn from green to bright red as they mature. These fruit lose their fleshy red outer covering as they age, exposing a fibrous brown under-surface. The seed itself is brown, round, and about 8 mm across.

Reproduction and dispersal 

This species reproduces only by seed. The relatively small fruit are presumably dispersed by birds, bats and other animals. They are probably also spread by water and in dumped garden waste.

Similar species 

Alexandra palm (Archontophoenix alexandrae) is very similar to the locally native bangalow palm (Archontophoenix cunninghamiana). These two species can be distinguished from each other by the following differences: Alexandra palm (Archontophoenix alexandrae) has a relatively wide trunk (up to 30 cm thick) that is usually expanded at the base (up to 50-60 cm thick at ground level). The sheath-like bases of the leaf stalks (i.e. crownshaft) are bright green or light green in colour. The leaf undersides are whitish-green or silvery and have no scaly outgrowths (i.e. ramenta).bangalow palm (Archontophoenix cunninghamiana) has a relatively wide trunk (up to 30 cm thick) that is slightly expanded at the base (up to 40 cm thick at ground level). The sheath-like bases of the leaf stalks (i.e. crownshaft) are dark green, brownish-green or dull purplish-green in colour. The leaf undersides are pale green and have scaly outgrowths (i.e. ramenta) along the veins.

Replacement species 
bangalow palm (Archontophoenix cunninghamiana)