dicksonia

( dik - SOH - nee - uh )

At-A-Glance Information

This genus of tree ferns needs full sun in cooler climates (partial shade in warmer ones), and regular water to perform well in the garden. These large ferns are hardy and slow-growing, native to the Southern Hemisphere. They grow to reach up to 15-20 feet tall when mature in most gardens, and can add a tropical, Jurrassic, or woodland feel to many shaded, moist, and sheltered areas of the landscape. Take care when planting these ferns in the landscape, as the spores produced by mature fronds can cause skin and eye irritation.

dicksonia Species and Varietals

The genus Dicksonia includes between 20 and 25 species and is the type genus member of the plant family Dicksoniaceae. The genus is named for prominent nurseryman and botanist James Dickson. The best growing zones for Dicksonia vary depending on the species. For more information, see the species descriptions below. To find your zone, click here: Zone Map.

Dicksonia antarctica (Tasmanian Tree Fern, Soft Tree Fern, Man Fern, Australian Tree Fern)
This species grows well in USDA hardiness zones 9-11 or Sunset growing zones 8, 9, 14-17, 19-24 and H1. It is native to southern Australia and Tasmania. This is a hardy tree fern, taking temperatures down to 20 degrees Fahrenheit. It reaches 15 feet tall and has a thick, red-brown fuzzy trunk. Fronds are 3-6 feet long and arch nicely. This species is considered invasive in the Azores, specifically on São Miguel and Madeira Islands.

Dicksonia squarrosa (New Zealand Tree Fern, Rough Tree Fern, Whekī)
This species is best in USDA hardiness zones 9 and 10 or Suset growing zones 17, 23, 24 and H1 and is native to New Zealand. Trunk is slender and dark in color, reaching 20 feet tall at maturity. Leathery fronds form a flat crown and are 8 feet long with white undersides.

Caring for dicksonia

Take care when planting these ferns in the landscape, as the spores produced by mature fronds can cause skin and eye irritation. It is advisable to wear gloves and eye protection when handling mature fronds to avoid injury. Plant Dicksonia 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 5.0 and 7.5 (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

Dicksonia, or 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 Dicksonia by Division
Spores produced by mature fronds can cause skin and eye irritation. It is advisable to wear gloves and eye protection when handling mature fronds to avoid injury. This type of propagation is relatively simple; you will need gloves, eye protection, 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:
  1. 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.
  2. Start to tease apart the roots with your gloved fingers. Once the roots are untangled, separate your plant into segments, ensuring that each one has at least one thick root section attached.
  3. 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.
  4. 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

Dicksonia tree ferns are susceptible to the following pests and disease issues in landscapes:
  • Root Rot
  • Scale Insects
  • Mealybugs
  • Spider Mites
For more information on these pests and diseases, including how to treat and prevent them, consult the following pages:

Gallery

Although these ferns start out small, they can attain heights of 15-20 feet over time.
Use Dicksonia ferns to add drama and a tropical feel to landscapes.
This small border features a Dicksonia tree fern, Saxifrage, Japanese Forest Grass, Lady Fern, and Cast Iron Plant.

Videos

A guide to Tree Ferns.
Tasmanian Tree Fern is featured in this shady garden.

Resources

How to Grow Dicksonia - Tasmanian Tree Fern
Dicksonia antarctica (Soft Tree Fern)
Wikipedia: Dicksonia
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 288, Dicksonia