Scientific Name: Cyathea cooperi
Common Names: lacy tree fern
Plant Type: Tree fern
Environment: Best in well-drained, rich soil. Full shade to partial shade/sun. Will tolerate light frost, but fronds may be damaged. Once established it is tolerant of dry spells.
Bloom: Sori containing spores occur in rows with up to 10 sori in each row, on the underside of the fronds.
Uses: Invasive in tropical climates; grows quickly when young; great in containers and good for that tight spot that has plenty of overhead space and not as much garden space (once it develops a trunk.)
Other: Named after Daniel Cooper (1817-1842), curator of the Botanical Society of London. When young, tree ferns can grow up to one foot per year. Young, uncurling fronds are often eaten in the wild by animals; humans have also used them as a food source including the pith from the center of the trunk as a source of starch.Video of Cyathea cooperi from SF In Bloom. A thorough and well-produced video on the fern lifecycle
The planting of tree ferns in Golden Gate Park goes back to the early years of the 20th century. They have thrived in San Francisco's mild climate as well as under the protection of the canopy trees above them. Their lacy crowns of emerald-green fronds impart an air of tropical profusion amidst the cool, foggy atmosphere. As with other ferns, they grow from stems underground but also can spread above ground. But in stark contrast to other ferns, they can produce a caudex or trunk growing three to 45 feet or even more. These trunks are non-woody and produce new fronds from the top. There are over 700 species of tree ferns. One of the most common in cultivation, including in Golden Gate Park, is Cyathea cooperi.
Cyathea cooperi is native to eastern Australia, but it thrives in many other places in the world where there are mild winter temperatures, dappled sunlight and plenty of moisture. It can also become invasive, particularly in tropical and warm temperate regions like Hawaii. The pale trunk, which can reach 30-40 feet, is marked with contiguous oval scars from older fronds. The pinnae or leaflets are divided several times, giving Cyathea cooperi its 'lacy' look. The new fronds or 'fiddleheads' are particularly beautiful, curled up with a delicate covering of silky hairs. They are often called 'crosiers,' as they resemble the staff bishops carry in religious ceremonies. The undersides of the mature fronds are covered with dusty brown sori aligned in rows. These sori protect the developing masses of dusty brown spores.
Dicksonia antarctica, native to Tasmania and eastern Australia, is also widely planted in the Park. It tolerates far lower temperatures than Cyathea cooperi. Its trunk is rough and covered with the broken off remnants of spent fronds. Look for both species in the Ancient Plant Garden and the Australia Collection alongside other species of tree ferns.
IN BLOOM CONTRIBUTORS:Photos by Docent Joanne Taylor; text by Docent Kathy McNeil; profile by Associate Curator David Kruse-Pickler