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Why is the Australian Tree Fern (ATF) an Invasive Species?

Australian tree fern (Sphaeropteris cooperi) is an invasive species in Hawai’i, scoring a whopping 16 on the Hawaii Pacific Weed Risk Assessment. This ornamental plant has escaped cultivation and is considered invasive for a variety of reasons. It outcompetes native plants in the forest by growing faster and taking up valuable canopy space. It can also easily spread through tiny dust-like spores that are found underneath its fronds. These spores are readily taken up by the wind or animals and can be dispersed as far seven miles from the original parent plant location.

How to quickly identify ATF?

Australian tree fern (ATF) is an expert at camouflage because it is commonly mistaken for a variety of different native tree ferns. Hāpu’u is the common Hawaiian name for a few different species of tree ferns that are native to Hawai’i. There are many differences between ATF and the different types of Hāpu’u but the quickest way to identify is by looking at the “crown” of the tree fern (the top of the tree fern where new fronds emerge) and checking to see what color the hair is. If it is white/ silvery and a skin irritant it’s ATF. If it’s not, it is most likely a different tree fern.

Other key differences include overall silhouette, and the trunk. The silhouette of ATF resembles a martini glass while Hāpu’u has more of an arched shape. The trunk of the ATF is skinny and has a ‘scaly’ texture from where the fronds fall off from and is hard when touched. Whereas Hāpu’u has a thick, soft fiber wrapping.

What can you do?

ATF is often sold and planted in gardens. To prevent further human spread don’t buy ATF when offered in stores or nurseries. Supply and demand dictates where and in what quantities ATF is sold. If the big box stores can’t sell it, they lose incentive to put it on the shelves again. 

You can also write to your legislators! Follow this link (https://www.capitol.hawaii.gov/fyl/) and you can type your address or zoom in on the map, select the district on the map, and click the arrow on the right side of the blue box. The web page will redirect you to a page with your legislators’ contact information. Please note some districts have multiple legislators you can contact, so be sure to contact whomever you’d like or message all of them. You can also contact the Hawai’i Department of Agriculture at (https://hdoa.hawaii.gov/contact/) and relay your concerns.

To learn more about ATF, follow these resources:

https://www.ctahr.hawaii.edu/invweed/WeedsHI/W_Sphaeropteris_cooperi.pdf

Humans have been moving plants around the world for centuries. Hawaiʻi is a prime example of just how far humans have transported plants. Many of the plants we’re accustomed to seeing in local gardens, parks, and landscapes aren’t actually native to Hawaiʻi. But just because a plant is introduced to an area doesn’t necessarily mean it falls into the “invasive species” category. In fact, many introduced species, such as ʻulu, avocado, and lychee, are an integral part of what makes Hawaiʻi special. Once a plant starts causing harm to humans or the native ecosystem, it’s looked at with more scrutiny.

Post L. hildebrandiana removal.

Take the Giant Burmese Honeysuckle (Lonicera hildebrandiana) for example. Giant Burmese Honeysuckle (GBH) has a vigorous climbing habit and requires strong support to handle the weight of the plant. In 2017, BIISC staff observed approximately 25 plants growing up several ‛ōhi‛a trees near the Kilauea Lodge in Volcano. They have been observed to have caused some limb breakage and can possibly lead to the whole tree coming down, which is particularly concerning because the fungal pathogen that causes Rapid ‛Ōhi‛a Death enters ʻōhiʻa through open wounds. When the GBH is well-established, the dense mat of vines and roots can also inhibit the growth of native seedlings. Since its population is fairly limited, BIISC staff is working to eradicate it from the Big Island.

(L) On a clear day, L. hildebrandiana leaves appear light green climbing a ‛ōhi‛a trees. (R) On an overcast day, L. hildebrandiana leaves appear darker in color as they climb through ‛ōhi‛a trees and hapu’u.

What does it take to eradicate invasive species from Hawaiʻi Island?

It can take years to fully eradicate an invasive species from the island. First, we map out the known populations and the extent of the plant’s distribution. So far, GBH has only been observed growing in Volcano Village. Its close proximity to Hawaiʻi Volcanoes National Park underscores why it’s so important to control its spread. To accurately gauge a plant’s population, we depend heavily on reports from the public because successful eradication means that every plant is eliminated. Our invasive plant response team is highly skilled and trained in various methods of plant control.

Have you seen this plant? Report it!

At BIISC, our plant control team takes a proactive approach by focusing on finding new invaders early, and removing them before they become widespread and more costly to control. Giant Burmese Honeysuckle is one of 10 eradication targets at BIISC. 

Report suspected plants to BIISC at (808) 933-3340 or email at biisc@hawaii.edu.