Contrary to its name, the Australian tree fern (Cyathea cooperi, also known as Sphaeropteris cooperi) is actually more tree than fern. Typically, when we think of ferns, we envision plants such as the painted ferns (Athyrium niponicum) or autumn ferns (Dryopteris erythrosora) , which achieve a mature height of about 18 to 24 inches.
But, in its native habitat of Australia, a tree fern can grow up to 50 feet tall. This tropical plant is easily too tall for most indoor growing situations except for large conservatories and greenhouses. Still, if your space and environment allow, it can be a beautiful addition to your landscape.
Characterized by lacy, feathery fronds that grow from 10 to 20 feet in length and a hair-like, scale-covered trunk, the fast-growing, evergreen Australian tree fern can bring an exotic touch to any garden. It's best planted in the early spring and prefers warm temperatures and partial shade year-round.
|Common Name||Australian tree fern, Cooper's tree fern, lacy tree fern, scaly tree fern|
|Botanical Name||Cyathea cooperi|
|Plant Type||Evergreen fern|
|Mature Size||Typically 15–25 ft. tall, 10–12 ft. wide; up to 50 ft. tall in the wild|
|Sun Exposure||Partial sun|
|Soil Type||Moist, well-drained|
|Soil pH||Neutral, acidic|
|Hardiness Zones||8–11 (USDA)|
|Toxicity||Not toxic to humans or animals|
Watch Now: How to Grow and Care for an Australian Tree Fern
Australian Tree Fern Care
Australian tree ferns thrive in mid-elevation tropical environments where they can sometimes be found growing in great, prehistoric forests swathed in tepid mist. The key to growing a healthy Australian tree fern is to provide it with dappled sunlight or shade, ample humidity, and consistently moist soil. these plants are tolerant of salty winds near coastlines, but they do not tolerate salty soil conditions.
The trunk of the Australian tree fern starts out as a low, wide clump and spreads as much as six feet in a year before growing upward into a single slender trunk covered in glossy, ginger-brown hairs. The fronds are broad, bright green with triangular lacy leaves; they do not change color in the fall, and do not bear flowers or fruit.
The Australian tree fern is one of the most commonly-seen tree ferns in the tropics, but unless you live in Australia or a similar region, you might have to go out of your way to purchase one. They're mostly grown as large, potted ornamentals in the United States and, when they are grown outdoors, are found mainly in public gardens and arboretums in tropical or semi-tropical zones. The plant has naturalized itself in Hawaii, where it's regarded as invasive due to its fast growth and prolific self-propagation via its spores.
Although Australian tree ferns are shade-loving plants in general, they can also thrive in partial sun or dappled sun locations where they receive six hours of light a day. Keep in mind that the more direct sunlight the plant receives, the more likely it is that you'll need to increase your watering schedule.
Australian tree ferns can tolerate a variety of soil conditions including sand, loam, and clay. That being said, they will thrive best in a moist, loamy mixture that is rich but well-draining with a neutral to acidic pH level. It's also recommended that you add a layer of mulch around the tree, which will add more nutrients to the soil and act as a barrier to seal in moisture (particularly during very hot weather).
Keep the soil moist at all times. Australian tree ferns are not drought-tolerant and need weekly watering. In extremely dry weather conditions, their need for moisture and humidity is extremely important. Avoid watering the crown directly because it can cause rot—instead, water the trunk and ensure the soil is consistently moist.
Temperature and Humidity
Australian tree ferns like a consistently warm and humid environment with temperatures ranging from 65 to 80 degrees Fahrenheit. Australian tree ferns do not acclimate well to rapid changes in humidity or temperature, which can result in browning fronds. In colder areas, you can grow the fern in a container, which gives you the flexibility to move it indoors for the fall and winter once temperatures drop too low.
During the growing season, feed your Australian tree fern monthly with a liquid fertilizer. Larger specimens are heavier feeders and might require feeding every other week year-round. For the amount of fertilizer to use, follow the instructions on the fertilizer label.
Types of Australian Tree Ferns
About 1,000 different kinds of tree ferns are found in tropical or subtropical settings.
- 'Brentwood' is a cultivar that grows faster than most tree ferns and is larger with darker green fronds than the species.
- The New Zealand or Tasmanian tree fern is closely related, but the species is actually Dicksonia antarctica, and it tends to have a narrower crown than the Australian tree fern (but has similar requirements).
Propagating Australian Tree Fern
Australian tree fern can only be propagated from spores. You cannot propagate this tree fern vegetatively from cuttings.
- Collect the spores from a mature frond onto a piece of paper.
- In a heatproof bowl, pour boiling water over soilless potting medium to sterilize it and remove any pathogens, which can affect germination. Let the potting mix drain and cool completely before filling it into a four-inch pot.
- Sprinkle the spores on the potting mix and cover it with a plastic dome or bag.
- Place the pot in a location with a consistent temperature of around 68 degrees Fahrenheit and indirect light.
- Keep it moist at all times, The spores will take 2 to 6 weeks to germinate.
Potting and Repotting Australian Tree Ferns
An Australian tree fern will grow rapidly, so make sure you plant it somewhere in your landscape where it has room to grow and expand. If you're growing your tree fern in a container, repot it annually into a larger pot (with fresh soil). Because the tree fern is susceptible to root rot, make sure the container has large drainage holes. Plastic pots don't dry out as fast as clay pots so they are generally more suitable for this type of fern that needs to be kept moist at all times.
When the plant reaches the maximum size allowed by the growing space, stop repotting to slow down its growth. Eventually, it will likely outgrow both the pot and the room.
The Australian tree fern is a fairly hardy tree fern that can tolerate occasional low winter temperatures of 20 degrees Fahrenheit in temperature zones USDA 8 through 11. But to protect the fronds from cold damage, it is best planted in a sheltered spot such as the side of the house that is protected from strong winds.
In addition, the roots of Australian fern grown in containers can be damaged in the winter due to their lack of insulation. Winterizing the container by wrapping it with bubble wrap gives it extra protection.
Common Pests & Plant Diseases
While the Australian tree fern doesn't have any major issues with diseases or pests, it can occasionally get mites or mealybugs. The first treatment recommendation is to spray the infestation with strong streams of water; if that doesn't work, treat the plant with neem oil or an insecticide until all signs of infestation have gone.
Are Australian tree ferns fast growers?
In the wild, Australian tree fern is the fastest-growing of the tree ferns. As a potted plant, it grows not quite as much but it is still a fast grower with an annual growth rate of up to three feet.
Are Australian tree ferns hardy?
The tree fern is a tropical plant that is only hardy in USDA hardiness zones 9 thru 11. In cooler climates, it can only be grown as a container plant and must be moved indoors before the first frost.
Do you cut back tree ferns?
Tree ferns do not require pruning, but for a neater appearance, you can remove withered and dead fronds. Also remove any fronds that are heavily infested with pests such as mealybugs and spider mites to control the spread of the pest.
“Australian Tree Fern.” Hawaii Invasive Species Council, 21 Feb. 2013, https://dlnr.hawaii.gov/hisc/info/invasive-species-profiles/australian-tree-fern/
“Sphaeropteris Cooperi.” Ncsu.edu, https://plants.ces.ncsu.edu/plants/sphaeropteris-cooperi/