Cyathea

( SYE - ath - ee )

At-A-Glance Information

Known commonly as Australian Tree Fern, this species of tree fern is a very fast-growing, hardy fern grown in full sun to partial shade. It can take temperatures down to 20 degrees Fahrenheit, but will take some damage to the fronds at this temperature. These plants eventually reach 20 feet tall and 12 feet wide, and start out as low clumping plants. Foliage is bright green and finely cut with brownish hairs on frond undersides. The hairs can cause skin irritation, so take proper precautions when working with these plants. The variety 'Brentwood' is a more robust, hardy form of the species. These plants are also sold under the names Alsophila australis, Alsophila cooperi, and Sphaeropteris cooperi. The best growing zones for Australian Tree Fern include USDA hardiness zones 9-11 or Sunset growing zones 15-24, H1 and H2. To find your zone, click here: Zone Map.

Caring for cyathea

Plant Cyathea in a space in the landscape that receives full sun; ideally, they appreciate between 6 and 8 hours of sun each day for the best growth. Ensure that soil is well-draining, rich in nutrients, and has a pH of between 5.5 and 7.0 (slightly acidic to neutral). If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Apply a layer of mulch around the planting area to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water new plantings regularly as they establish a strong root system in their new home. At maturity, these plants perform well in consistently moist soils, but should not be left in soggy conditions, as this will lead to root rot problems. In dry climates, these trees will need to be sprayed with a hose (including the trunk and fronds) on warm days.

Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. Pruning is simple; remove any damaged, diseased, or dead foliage at any time during the growing season. Australian Tree Ferns are considered long-lived perennials, able to survive in the landscape for several hundreds of years in their native environments. In garden cultivation, their life span is shortened to between 30 and 100 years.

Propagation

Cyathea, or Australian Tree Ferns, are best propagated through division of existing plants. Spores can be used to propagate as well, though doing so requires more specialized knowledge, previous experience, and a suitable medium. To learn more about propagating ferns via spores, see the Propagation module. To propagate your Australian Tree Fern, follow the directions below:

Propagating Cyathea by Division
This type of propagation is relatively simple; you will need a clean shovel, mulch, fresh soil, compost and pots (only necessary if you will be saving divided plants for transporting elsewhere). Division is best done in early spring. To propagate by division, follow these steps:

Using a shovel, dig up your existing plant. Start from the outside and work your way in to avoid damaging the root(s). Once you have worked it up out of the ground, lay it out.
Start to tease apart the roots with your fingers. Once the roots are untangled, separate your plant into segments, ensuring that each one has at least one thick root section attached.
Prepare your pot(s) or new planting site(s) with amended, well-draining soil. You can either bring in new soil or simply amend your existing soil with compost to complete this task. Then, plant your divisions and water thoroughly.
Apply a thick layer of mulch over the new planting to protect it from cold weather as it acclimates to its new home. Then, enjoy watching it sprout in the next growing season.

Problems and Pests

Take care when planting these ferns in the landscape, as they are considered invasive in Hawaii, Mauritius, Reunion, the Azores, South Africa, New Zealand, and Australia. Consult with local authorities before installing. Cyathea tree ferns are generally free of most pest and disease issues, but can have some problems with the following if growing conditions are not ideal: