The Quiet Invaders—Death by a Thousand (Literally) Cuts

19 Jun
Shoebutton elliptica.  It has been mistaken for the native Marlberry. By JB.

Shoebutton Ardisia. Once popular in gardens, this Ardisia is related to and has been mistaken for the native Marlberry. (By JB)

In Palm Beach County:

Grasses: 135 total vascular plant species growing wild, 45 species non-native, 33% non-native

Sedges: total 83 total, 13 non-native, 16% non-native

Asteraceae: 95 total, 18 non-native, 19% non-native

Rubiaceae: 23 total, 7 non-native, 30% non-native

All Florida Vascular plants: 4289 total, 1421 non-native, 33% non-native

(Data from USF Atlas of FL Vascular Plants)

Every nature enthusiast decries the invasive exotic bioinvasion of Florida and worldwide. Brazilian Pepper and Climbing Fern make us cuss. We battle unwelcome Laurel Figs and Java Plums on public lands. We grouch about those who love their beachside Casuarinas. And then come the Pythons, Walking Catfish, Cane Toads, Cuban Treefrogs, and snails that look like tennis balls. (Are these good for Limpkins?) Invasive microbes and arthropods are a scourge. We know, we know.

But it is even worse than it looks. For every invasive species we know many more sneak in virtually unnoticed .

A quick and approximate survey of species growing “wild” in Palm Beach County makes the point painfully. Looking at four large plant families—the grasses, sedges, composites, and coffee family, the percentages of non-natives species are 33, 16, 19, and 30. Eighty three non-native species in Palm Beach County alone. Or statewide 1421 non-native species accounting for 1/3 of the flora. We have more invasive exotic species growing loose in Florida than the number of native species in Hawaii!

Cuban Bulrush forms floating mats.

Cuban Bulrush forms floating mats. (JB)

I don’t have data, but 1/3 of a diverse flora being non-native begs unanswered questions concerning crowding, allelopathy, competition, hybridization with native species, alterations to the soil ecosystem, impacts on wildlife, altered fire patterns, collateral pests and diseases, and more. Is Global Warming a factor?

So it’s not all Melaleuca. And, by the way, Melaleuca’s close relative, a garden favorite, Weeping Bottlebrush (Callistemon viminalis) is adding its red beauty to certain natural areas in Florida. Why don’t we just dub it Bloody Melaleuca?

Some of the invaders are pretty, or novel, and interesting. The other day I waded into a canal for a better look at an overhanging branch bearing what I thought was Skunk Vine (Paederia foetida) in a new locale. Wrong! (I hate being blind.) But you might not have to wait long to enjoy Skunk Vine on a branch near you. The flowers are showy. And even more fun nomenclaturally, and so far limited to the Miami Area, is Sewer Vine, Paederia crudasiana, which, I’m sorry to say, makes me wonder what a crud-ass looks lie. (Sorry, blog-writer’s license)

Skunk Vine is prettier than its name. (by GR)

Skunk Vine is prettier than its name. (GR)

Speaking of runaway vines, Mile-a-Minute Vine (Mikania micrantha) is pondering the possibility of over-running Florida from a start in Miami. Why has it remained localized so far?

Trying to figure out which ferns are truly native is next to impossible. If you think otherwise, compare every source you can find dealing with the genus Nephrolepis. If you get it figured out definitively and with consensus, please let me know. And to make it worse, fern spores blow long distances on the wind, and ferns are especially good at hybridizing.

Native Boston Fern?  No, invasive Asian Sword Fern.  Mighty similar!  (Boston Fern has light tan shagginess sticking out on the leaf stalk.)

Native Boston Fern? No, invasive Asian Sword Fern. Mighty similar! (Boston Fern has light tan shagginess sticking out on the leaf stalk.)

So what can you do? Bulldozers, machetes, brigades of volunteers and herbicides are not enough. I heard someone say recently, “sometimes all we’ve got is resignation.” Just like crime and reality TV, we’ll never shed the curse, but at least there is one little thing we could do:

Abandon the 19th Century social cachet attached to “I have an exotic plant you don’t have,” and mature to a 21st Century preference for the native species that belong in our own back yards. Oh yea, right, I’m preaching to the other preachers.

"Mexican Petunia" is not Mexican, and is not a Petunia.  It remains popular in landscapes despite being a Category I Invasive Exotic invader.

“Mexican Petunia” is not Mexican, and is not a Petunia. It remains popular in landscapes despite being a Category I Invasive Exotic.


Posted by on June 19, 2013 in Uncategorized


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4 responses to “The Quiet Invaders—Death by a Thousand (Literally) Cuts

  1. Diane Goldberg

    June 21, 2013 at 11:06 pm

    It’s disheartening to see so many non-natives being grown as well as all the escaped plants everywhere. I grow mostly natives, though I have some non-invasive fruit trees & herbs. I have seen Crotalaria spp. at the Port St. Lucie Botanical Gardens, which I’ll be removing. I was suprised that it wasn’t on the FLEPPC invasive list. I’ve also been seeing Gaura lindheirmeri growing on road sides, which means it’s more invasive than was expected. It has a tuber, which makes it hard to remove.

    • George Rogers

      June 22, 2013 at 8:02 am

      What surprises me in the history of horticulture are two things:
      1. Awareness of the problem goes way back in time.
      2. There seems to be a sense of “you just can’t tell what will escape.” No, not 100%, but if a species has wind-blown or bird-dispersed seeds I’d consider it a triple threat. Not rocket surgery. And of course there are many well-behaved exotics in our gardens, but even so, they are so often just not as good a “fit” eco-aesthetically.

      Are you sure it is Gaura lindheimeri? Certainly possible, given that it is a garden species native to Texas and LA, and garden species do escape plenty. I looked at the FL Plant Atlas and see only one FL locality…in the panhandle. If that species is on the loose on the Treasure Coast that is interesting and I’ll keep my radar on. Any chance it might be Gaura angustifolia? which is a common native species along roads and canals.

    • George Rogers

      June 22, 2013 at 3:51 pm

      Sorry, a slip of the mind. Should have said strawberry guava (or guava itself) while pulling a random example from the air. Re-edited the post to avoid defaming fruit.

  2. Victoria L. Merritt

    June 22, 2013 at 2:47 pm

    Hello, George. I’ve really enjoyed reading your posts. Much appreciated!

    Regarding the invasiveness of the Pineapple Guava, are you referring to the Strawberry Guava (Psidium littorale) rather than Pineapple Guava (Feijoa sellowiana)? The University of Florida database did not note that the Feijoa is invasive ( The article was last reviewed in 2011 so perhaps it was found more recently in natural areas.

    Thank you, Victoria Merritt


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