Family Arecaceae was previously Family Palmae.
Palms are native to, and common in widespread tropical and subtropical areas.
They are all descended from a single common ancestor.
Numerous plants in Brisbane are commonly, and incorrectly called ‘palms’. These include:
- the Banana palm in Family Musaceae,
- the Cabbage and Ponytail palms in Asparagaceae,
- the Cardboard palm in Zamiaceae,
- the Madagascar palm in Apocynaceae,
- the Pandanus and Screw palms in Pandanaceae,
- the Sago palm in Cyatheaceae and
- the large Traveller’s palm in Strelitziaceae.
Palms are divided into 5 subfamilies that are then divided into Tribes.
- Sub-families are the Arecoideae (Areca and Chamaedorea palms),
- Calamoideae (Calamus and Raphia palms),
- Coryphoideae (Caryota, Livistona, Phoenix, Sabal and Washingtonia palms)
- and Ceroxyloideae and Nypoideae.
Plants of the World Online accepts 183 genera with around 2,600 species.
Australia has palms in around 17 of these genera.
Flora of South East Queensland Vol. 3 lists the following as endemic here:
- Calamus muelleri the Southern Lawyer vine,
- Livistona australis the Cabbage Tree palm,
- Livistona (decipiens) decora,
- Archontophoenix cunninghamiana the Bangalow palm,
- Linospadix monostachya the Walking Stick palm and
- Syagrus romanzoffiana the Queen palm.
With such a large family only the main/common features are mentioned below.
Palms are evergreen perennial small (15 cm) to massive (60 m high) woody plants.
They can be tree-like, shrubby, prostrate, scramble or climb.
The primary root may be replaced by thick adventitious roots from the base of the stem.
They can be solitary or form clusters by branching once from near the base.
Some have an underground stem (trunk) but most have a single erect one.
Stems, typically cylindrical reach their full diameter before they extend upwards.
They are usually covered by persistent leaf bases, fibres, spines etc.
Leaves, mostly in a terminal cluster are alternate in a spiral or 2 ranks.
They usually have a grooved petiole that is smooth or has spines, prickles or teeth.
The expanded petiole base forms a tubular sheath down the stem.
Initially intact the sheath may later split.
Sheaths may form a pseudostem or crownshaft that protects the growing tip.
Blades up to 25 m long are always obviously folded (pleated) although a few may later flatten.
They are often split along the ridges into variously shaped leaflets or pinnae.
- Pinnate leaves have leaflets on 2 sides of an elongated midrib (feathered leaf).
Leaflets can be opposite, alternate or irregularly arranged on the midrib (rachis).
Some may be reduced to spines and the tips can be round, pointed or eroded. - Palmate leaves (fan-leaved).
Intact blades in a full or half circle are uncommon on mature leaves but often seen in juvenile ones.
Divided blades can have the divisions reaching the midrib (palmate), or be short of it (palmatifid). - Bi-pinnate or twice divided blades are uncommon to rare.
The often massive (over 7 m high) inflorescences are almost always axillary (lateral).
They can be below any crownshaft or within or above the leaves in the crown.
When terminal the stem dies after flowering.
Some are spikes but most are panicles that are branched up to 5 times.
They are usually enclosed then subtended by 1 to numerous bracts or spathes.
These can be membranous or leathery and may become woody.
The ultimate branches have 2 to a few flowers with bracteoles at the base.
The multiple small flowers may be on a pedicel or be directly attached.
Others are partially sunken into the midrib.
Most are greenish to cream or white, some yellow, orange, mauve or reddish.
Flowers are bisexual or uni-sexual with male and female on the same or different plants.
On one palm unisexual flowers may be on the same or different inflorescences or parts thereof.
There are often groups with 1 female and 2 male flowers throughout an inflorescence.
The small flowers typically have 3 sepals and petals either free or with their bases fused.
There are 3, 6 or 9 (rarely many) stamens that are free or fused basally.
Often the fused filaments form a tube or cup.
Anthers, dorsi- or basi-fixed mainly open sideways through long slits.
The 1 to 3 carpels forming the superior ovary are free or basally fused.
The 1 to 3 locules each have 1 ovule and the style is short or absent.
Male flowers have no, or an aborted ovary.
Female flowers have no stamens or just infertile staminodes.
Male and bisexual flowers open wider than the female ones.
There may be nectaries at the base of the ovary or the stamens.
Typical fruit are a 1-seeded drupe, rarely drupe-like (or a berry) with 2 or more seeds.
The small to massive (50 cm) fruit can be smooth, hairy, scaly or spiny.
Some are brightly coloured.
J.F.
