Sphaeropteris cooperi aka Cooper's Cyathea

Sphaeropteris cooperi is an evergreen tree fern from eastern Australia. Its native range includes Queensland and New South Wales. It belongs to the tree fern family, Cyatheaceae. Gardeners also call it Australian tree fern or Cooper's tree fern. One slim trunk holds a broad crown of arching fronds. NC State and RHS describe its growth as fast. Florida's profile instead lists slow growth.

Garden size varies across the sources and growing climates. NC State gives heights of 15–25 feet [4.6–7.6 metres]. Florida gives an upper height of 30 feet [9.1 metres]. RHS lists a smaller range of 8–13 feet [2.5–4 metres]. Reported garden widths span 8–20 feet [2.4–6.1 metres]. Wild plants may reach 50 feet [15.2 metres] tall. Brown, fibrous tissue and scales cover the trunk. Fallen fronds leave oval scars that spiral around it.

The green fronds have a fine, divided, lacy form. Their undersides are paler than their upper surfaces. NC State reports frond lengths of 13–20 feet [4–6.1 metres]. Stiff white hairs cover the young, curled fiddleheads. This fern makes neither flowers nor fruit. It grows from spores rather than seeds. Brown sori form rows beneath the leaflets, near the midrib. Growers can sow the spores once they ripen.

Partial to full shade suits this fern's needs. It needs steady soil moisture, warmth, and humid air. Rich soil must drain well despite staying moist. Acid or neutral sandy and loamy soils suit it. Florida also reports tolerance of clay with good drainage. Salt in soil or sea spray poses a problem. RHS rates it H3 for mild parts of Britain. NC State lists USDA zones 8–11; Florida gives 10b–11. In frost-prone areas, RHS advises winter shelter under glass. Keep that space at least 50°F [10°C]. Feed monthly while it grows, and remove dead fronds.

Use it as a specimen or shaded understory plant. Containers suit seasonal displays on decks and patios. Indoor plants need bright light, humidity, and ample room. Mites and mealybugs can attack it; termites may enter trunks. Disease causes few problems, but crown watering can cause rot. Sudden shifts in heat or humidity may brown fronds. NC State reports invasive spread in Hawaiian forests. Florida does not currently class it as a problem species.