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 picture plants such as painted ferns (Athyrium niponicum), which achieve a mature height of just 18 inches. But in its native habitat of Australia, a tree fern can grow up to 25 feet or more. This tropical plant is easily too big for most indoor growing situations except for large greenhouses. Still, if your space and environment allow, it can be a beautiful addition to your landscape.
Characterized by lacy, feathery fronds, and a hair-like, scale-covered trunk, the fast-growing Australian tree fern can bring an exotic touch to any garden. It's best planted in the early spring and prefers warm temperatures and plentiful sunlight year-round.
|Common Name||Australian tree fern, Cooper's tree fern, lacy tree fern, scaly tree fern|
|Botanical Name||Cyathea cooperi|
|Plant Type||Herbaceous, perennial|
|Mature Size||15–25 ft. tall, 10–12 ft. wide|
|Sun Exposure||Partial, shade|
|Soil Type||Moist, well-drained|
|Soil pH||Neutral, acidic|
|Hardiness Zones||9–11 (USDA)|
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 ample humidity and consistency. Additionally, these plants are tolerant of salty winds near coastlines, but not 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 there are no flowers or fruit.
The Australian tree fern is one of the most commonly-used tree ferns in the tropics, but unless you live in Australia or a similar region, you may have to go out of your way to get an Australian tree fern. 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 also naturalized itself in Hawaii, where it's regarded as invasive due to its fast growth and prolific self-propagation.
Although Australian tree ferns are shade-loving plants in general, they can also thrive in partial sun or full sun locations where they get over six hours of light a day. Keep in mind, the more direct light the plant receives, the more likely it is that you'll need to increase your watering cadence.
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, with especially high levels of moisture or humidity in dry weather. Avoid watering the crown directly as this can cause rot—instead, water the trunk and ensure it's 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, giving 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 with controlled-release fertilizer monthly, or biweekly with weak liquid fertilizer. Larger specimens are heavier feeders and may require feeding every other week year-round. For the amount, follow the instructions on the fertilizer label.
Types of Australian Tree Ferns
There are about 1,000 different kinds of tree ferns, all found in tropical or subtropical settings.
- 'Brentwood' is a cultivar that 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 growth requirements).
Propagating Australian Tree Fern
Australian tree fern can only be propagated from spores, not 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 4-inch pot.
- Sprinkle the spores on the potting mix and cover it with a plastic dome. Place the pot in a location with a consistent temperature of around 68 degrees Fahrenheit and in 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). As the 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 9 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 does not get any strong wind.
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. Try first removing the infestation with strong sprays 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 3 feet.
Are Australian tree ferns hardy?
The fern is a tropical plant that is only hardy to USDA zone 9. 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.