Look Out for These Invasive Plants in Hawaii

Albizia, miconia, and smothering seaweed are just a few of Hawaii’s most troublesome invasive plant species.
Written by Melanie Krieps Mergen
Reviewed by Melanie Reiff
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Albizia, miconia, and smothering seaweed are just a few of Hawaii’s most troublesome invasive plant species.
Invasive species present unique problems in island environments like Hawaii, where native species, many of whom are found nowhere else on earth, have had millions of years to interact and evolve in relative isolation. When invasive plants are introduced to Hawaii’s islands, they put a delicate balance in flux as they crowd out vulnerable native species that haven’t adopted strategies to compete with them.
So what invasive plants should you be on the lookout for in Hawaii?
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The top 10 invasive plant species in Hawaii

Species are deemed invasive for various reasons. Most often, it’s because the species isn’t native to the immediate area, and it presents a hazard to the environment, public health, or economically important factors. Some can even pose specific risks to your property by way of falling branches or increasing the likelihood of soil erosion and landslides.
If you discover an invasive species on the Hawaiian Islands, or you think you might have discovered one, the Hawaii Department of Land and Natural Resources (DLNR) directs you to report your sighting by calling the 643-PEST hotline (808-643-7378) or by visiting
643pest.org
. The website also has a
dashboard
where you can view other reported sightings of invasive species.
As a Hawaii resident, what invasive species should you keep an eye out for? Get familiar with them by taking a look at the list below.

1. Albizia

Scientific name: Falcataria moluccana
What it looks like: Large, towering tree that can grow up to 150 feet tall
Why it’s a problem: Albizia is problematic in Hawaii for a host of reasons—it causes significant changes to local soil’s nitrogen levels, it grows extremely quickly and outcompetes native species and blocks their sunlight, and it reduces the amount of suitable habitat for local birds.
There’s also the risk to human safety—its branches are prone to breaking off and dropping suddenly without showing any signs of weakness. For obvious reasons, this can also become a huge problem if an Albizia tree has branches hanging over your home or garage.
What to do: Non-hazardous albizia trees can sometimes be strategically treated with herbicide—you can find more information about the proper treatment methods from the
Big Island Invasive Species Committee (BIISC)
. Large trees that could pose a hazard to other structures or people should be removed by a certified arborist.

2. Rubbervine

Scientific name: Cryptostegia grandiflora, C. Madagascariensis
What it looks like: Plant with showy, white to pinkish-purple flowers and dark, glossy leaves; can grow as a climbing vine plant or a bush
Why it’s a problem: Brilliant as its bright flowers may be, rubbervine presents serious problems—so much so that it’s considered one of Hawaii’s most problematic invasive plants. They spread aggressively and can wrap themselves tightly around other plants, ultimately restricting their growth and depriving them of sunlight. 
It’s also extremely toxic to people and animals for the damage it can cause to the heart. Even if you’re not putting it on your plate, rubbervine is worth avoiding, as it can create a toxic dust when it dries that causes coughing, nose swelling, and eye blistering. Exposure to the plant’s milky sap can result in painful rashes and blisters.
What to do: Pick another plant for your garden! A single rubbervine seed pod can hold anywhere from about 300 to 800 seeds that can spread easily by both wind and water. If you have a rubbervine problem on your property, you can seek out help from the
Big Island Invasive Species Committee
.

3. Pampas grass

Scientific name: Cortaderia jubata, Cortaderia selloana
What it looks like: Grass with long, “saw-toothed” leaves and dry, curly, corkscrew-shaped leaves at its base that can reach up to 10 feet tall. Grows tall, fluffy flowering stalks. Can be confused with native Hawaiian sedges, but their leaves aren’t as sharp in comparison.
Why it’s a problem: Pampas grass is native to South America but spread throughout Hawaii (mostly Maui and Oahu) after being introduced as an ornamental plant. Like many invasive species, the problem with Pampas grass is that it can spread quickly and crowd out other native species. On top of that, the plant also presents a considerable fire risk.
What to do: There are a number of ways to get pampas grass under control. Some options include uprooting stalks early, mowing them down before they’re able to spread seeds, or covering large patches with tarp for a period until the pampas grass underneath dies off.

4. Barbados gooseberry

Scientific name: Pereskia aculeata
What it looks like: Plant that starts off shrublike when young but grows into a climbing cactus with thorny branches. Produces yellowish-reddish berries.
Why it’s a problem: Barbados gooseberry is a detriment to forested areas because it climbs trees up to the forest canopy, then blocks the trees and plants below from access to sunlight. 
What to do: Removal of Barbados gooseberry should be done carefully, because the plant can regrow from broken fragments. Check with the
Hawaii Invasive Species Council
for more guidance on how best to remove the plant.

5. Florida raspberry

Scientific name:Rubus argutus
What it looks like: Thorny shrub that produces berries that are bright red at first but darken to black when ripe
Why it’s a problem: Florida raspberries can create dense patches that crowd out other native species, and they can quickly overtake a variety of landscapes, like forest parameters, stream banks, bogs, and open grassland areas.
What to do: Plant a native fruit species on your property instead. Young plants can be uprooted early on, and spot-treating with the right type of herbicide can prevent regrowth after larger plants have been trimmed. Aim to remove the plants before they develop fruit.

6. Ivy gourd

Scientific name: Coccinia grandis
What it looks like: A vine that’s a member of the cucumber family; produces white flowers with five petals and smooth, bright red fruit that is one to three inches long once ripe
Why it’s a problem: Like the rubbervine, the ivy gourd spreads aggressively, wrapping itself around and smothering other plants. 
Ivy gourd plants do face one challenge when it comes to their spread: the plants are explicitly “male” or “female,” and they need to be near each other for successful pollination. When that happens, however, they can spread quickly and they’re difficult to contain. 
What to do: Repeated uprooting and removing underground tubers can limit ivy gourd spread. Be sure to contain any stems or other plant parts as you remove them, as they can sprout new growth.

7. Miconia

Scientific name: Miconia calvescens
What it looks like: Tree with distinctive leaves that have a bright purple underside and what the Hawaii DNR describes as a “leaf within a leaf” pattern on its veins. Produces dark purple fruit.
Why it’s a problem: Miconia can spread quickly—like, really quickly, on account of the fact that miconia trees can produce as many as ten to twenty million seeds in a single year, according to the Hawaii DNR. Comparable in size to a grain of sand, they’re able to spread quickly and quietly. 
They also reach maturity quickly, and once they do, their broad leaves block sunlight from other competing plants. That reduces the amount of viable habitat that Hawaii’s endangered species have access to. 
Each tree’s shallow roots can also make areas where it spreads more susceptible to soil erosion and landslides, which could affect the well-being of your own property if there’s an infestation nearby.
What to do: Thanks to its shallow roots, it’s pretty easy to uproot miconia. Tread with caution (literally) if you come across the plant yourself, as they can hitchhike on clothing and footwear unnoticed. The
Hawaii DNR
has been studying the potential of deploying caterpillars that feed on miconia to help limit its spread. 

8. Fireweed

Scientific name: Senecio madagascariensis
What it looks like: Yellow flower that appears similar to a daisy, reaches about 5 inches in height
Why it’s a problem: Fireweed is small but mighty. It presents a significant danger to livestock like cattle as well as horses because it’s extremely toxic to them and tends to grow in areas where they might graze.
What to do: Regular hand-pulling before fruiting as well as spot treatment with the right kind of herbicide can prove effective in keeping fireweed under control.

9. Bishop wood

Scientific name: Bischofia javanica
What it looks like: Large tree that produces clusters of round fruit 
Why it’s a problem: Bishop wood trees disturb forested areas and compete with native Hawaiian species.
What to do: Plant one of Hawaii’s many native fruit varieties instead, and report bishop wood trees if you see one.
MORE: What is the Beautification Fee in Hawaii

The five most invasive aquatic plants in Hawaii

Invasive plants also create major problems for Hawaii’s marine environment. Invasive algae species are particularly troubling for the problems they create for Hawaii’s sensitive coral reef habitats.
Invasive species sightings can be reported to the DLNR’s
Division of Aquatic Resources
.
The following are five of Hawaii’s invasive aquatic plant species.

1. Cattail

Scientific name: Typha latifolia
What it looks like: Wetland plant with long, thin, green stem and leaves. The flowers crowning the stems are comparable to cigars or corn dogs.
Why it’s a problem: Cattail is native to many places, but not Hawaii, where it can grow in dense patches and crowd out space that endangered native species, like the Hawaiian stilt and the koloa duck, depend on. 

2. Smothering seaweed

Scientific name: Kappaphycus alvarezii, Eucheuma SPP.
What it looks like: Seaweed that grows in thick mats with intertwining branches
Why it’s a problem: Just like the name implies, smothering seaweed spreads quickly and smothers corals, depriving them of access to sunlight. 

3. Prickly seaweed

Scientific name: Acanthophora spicifera
What it looks like: Seaweed that can appear pink, brown, green, or yellow in color
Why it’s a problem: Prickly seaweed can reproduce when plant fragments fall off, allowing for a rapid spread that crowds out native marine life. They can become particularly problematic in shallow reef environments.

4. Keyhole sponge

Scientific name: Mycale armata
What it looks like: Bright orange sponge that can grow up to a meter in diameter
Why it’s a problem: The orange keyhole sponge is mesmerizing for its bright colors, but it competes with Hawaii’s native corals and sponges found on patch reefs.

5. Leather mudweed

Scientific name: Avrainvillea lacerata
What it looks like: Small, fan-shaped leaves protrude from a thick mat
Why it’s a problem: Leather mudweed is impressive for its hardiness amid environmental extremes, but the mud it surrounds itself with dramatically alters reef habitats and the species that live among them.

How to save on homeowners’ insurance in Hawaii

You may not always have a say in whether or not invasive species find their way onto your property, but having the right
homeowners insurance
in place can give you vital protection from the species that pose a real threat to structures, like the albizia tree and its falling branches.
It doesn’t have to be costly, either. With the
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