Osmunda regalis

Royal fern

Family: Osmundaceae

Origin: Africa, Eurasia, North and South America

Royal fern growing in a cluster.
Fronds are less than 3m in length. Forms dense stands to compete with native vegetation.

Regional Pest Management Plan (RPMP) status

  • Aotea — Progressive containment
  • Parkland with Significant Ecological Areas — Site-led
  • Waitākere Ranges Heritage Area priority status
  • Whole region — Sustained control
  • National Pest Plant Accord Species

View more about the RPMP statuses

General description

Perennial deciduous rhizomatous fern. Fronds are < 3 m long, bi-pinnate and dimorphic, with sterile pinnae at base and reduced fertile pinnae at apex. Sporangia clusters are borne on fertile fronds during spring – autumn.

What you need to know

To help protect our environment:

  • You must not breed, distribute, release or sell royal fern. As royal fern is a National Pest Plant Accord species, these restrictions apply within the Auckland region and across the whole of New Zealand.
  • You must not plant royal fern within the Auckland region, unless you are transferring an existing plant on your land to another location within the boundaries of the same property.
  • You must destroy any royal fern on land that you occupy if it has been planted in breach of the above rules and you are directed to do so by an authorised person.

Auckland Council will manage royal fern at all sites within the Aotea/Great Barrier Island group where it is known to occur.

If you see royal fern anywhere on Aotea/Great Barrier Island group, please report it to Auckland Council at pestfree@aucklandcouncil.govt.nz.

Habitats

Wetlands, still or slow-moving water body margins and flood zones, sand dunes, ditches, semi-open canopy forests.

Dispersal

Spores dispersed by wind.

Impact on environment

Forms dense stands and is likely to compete with native vegetation and restructure habitat. Potential to obstruct access, reduce enjoyment of and impact mauri of wai māori.

Control

Site Management

Follow up treated areas 3 times per year. Encourage natural regeneration of native plants or replant treated areas where possible after 2-3 treatments to establish dense ground cover and minimise reinvasion. Ensure correct identification and it is not a native fern.

Recommended approaches

Do not attempt to undertake control of this species on Aotea/Great Barrier Island group. Please report to Auckland Council if seen on Aotea/Great Barrier Island group.

Physical control

Method: Dig out.

Plant parts requiring disposal: Spores on leaves.

Disposal options: Remove to greenwaste or landfill if practical.

Biocontrol

Biocontrol is currently not available for this species.

Community agrichemical control recommendations

Basic Growsafe certified: Cut stump and spray freshly cut base with 1g metsulfuron-methyl per 1 L of water.

Certified Handler/Experienced agrichemical user: Foliar spray seedlings with 5g metsulfuron-methyl per 10L of water.

Caution: When using any herbicide or pesticide please read the label thoroughly to ensure that all instructions and safety requirements are followed.

A woman in the middle of a cluster of royal fern.
Changes local environments by forming dense undergrowth. Sheds all their leaves for part of the year.
Photo credit: Alastair MacArthur
Close up of royal fern.
Forms broadly divided bright green fronds. Crowned with rusty brown fertile sori spikes.
Photo credit: Alastair MacArthur
The small royal fern leaves laid out on a white background with the dried sori on the right.
The brown spore bearing stems are largely hidden by the main fronds of the plant, which are broad and slightly drooping.
Photo credit: Alastair MacArthur