Weeds: Give Them an Inch & They’ll Take Mile

A visit to the Sebastian Stormwater Park on 8/8/2020 was opportunity to see an unfortunate array of invasive pest plants, mega-weeds.  Seeing the proverbial silver lining, Karen Schuster (Class of 2007) remarked that property could have “grown homes”.

This 163 acre park was built by the St. Johns River Water Management District to filter stormwater before it reaches the Indian River Lagoon and to provide flood protection.  It lies in the center of Sebastian Highlands, a community built by General Development without a thought to flood protection or stormwater.  Two parking lots are located on Englar Drive between Schumman Drive and Barber Street.

Large open disturbed areas have allowed invasive pest plants to flourish.  They are presented here in alphabetical order.

Bishopwood (Bishopfia javanica)

The large and handsome  tree from Tropical Asia and Pacific Islands is an invader of disturbed hammocks. Bishopwood has distinctive compound leaves, sports quite attractive trunk rings when young, and flourishes in the hammocks at the Oslo Riverfront Conservation Area (ORCA).

Carrotwood (Cupaniopsis anacardioides)

This ornamental tree with compound leaves and an orangish tap root is on the Florida Noxious Plant List, which prohibits its cultivation and sale.  Unfortunately, its prohibition came far too late, after it was much-planted as a landscape ornamental.  It invades many natural areas including hammocks, coastal wetlands, spoil islands, and neighbor’s yards.  Birds, especially crows, and other wildlife spread its seeds.

Air potato (Dioscorea bulbifera)

This aggressive vine greeted us as we left the shady parking area nearest to Barber Street.  While we saw a bit of damage from the air potato beetle, a biological control agent, this terrible vine was overwhelming much of this hammock area, just as it does at ORCA.  Though it rarely flowers in Florida, it nonetheless produces a bounty of bulbils (“air potatoes”) almost all of which sprout even in very shady conditions.  It dies back to the ground in winter to re-grow with a vengeance in the spring.

Cogongrass (Imperata cylindrica) 

This yellow-green grass with an off-center midrib is regarded as one of the world’s worst weeds and is on Florida’s Noxious Plant List.  Most (2/3) of the biomass is underground.   We see this hideous grass at both north and south ORCA, as well as along Oslo Road.  Control is difficult and requires repeated applications of herbicide.  Large patches infest many roadways and are recognizable by their color even at high speeds.  This plant was brought to Florida as a forage grass and escaped cultivation.

Old World Climbing Fern (Lygodium microphyllum)

This horrible fern climbs over other plants and kills them.  The frilly leaves are fertile fronds.  Winds and water spread the spores of this particularly pernicious plant.  Note the wiry rachis (central stem).  Be on the look-out for this plant in moist places at ORCA (especially along the Florida Department of Transportation drainage ditches), in your yard, and even in your potted plants.

Peruvian primrosewillow (Ludwigia peruviana)

Native to tropical America, this yellow-flowered shrub with alternative leaves grows in moist places – ditches, pond margins, lakes, and swamps.  It out-competes native vegetation and has been known to clog waterways.  You sometimes will find it growing in the ditches along Oslo Road toward U.S. Highway 1.  Closer to the Indian River Lagoon where conditions become saltier, mangroves and other halophytes out-compete it.

Creeping oxeye (Sphagneticola trilobata)

Also known as wedelia, this aggressive groundcover has sunny daisy flowers and once was recommended for xeriscaping by the water management districts.  In this picture it is trying to overwhelm shortleaf wild coffee (Psychotria tenuifoliaa).  Even a tiny piece will root.  You will find lots of it growing along Oslo Road near the Florida Medical Entomology Laboratory and into the ditch.

Java plum (Syzygium cumini)

At first glance I thought that this plant was a strangler fig (Ficus aureum), but, when it lacked a milky sap, I knew that it was not.  Also known as jambolan or jambu, this large tree (to 75′) of African and Asian origin was introduced in the early 1900’s for its purple plum-like fruits that some say taste like glue.  It volunteers in light shade in moist-ish places and is not at ORCA (at least yet).

Guinegrass (Urchloa maxima)

This weedy grass is very variable and can grow to be from 3 – 16′ tall.  Its seeds are borne in open floppy terminal panicles, and you will find it growing in a variety of disturbed places including along roadsides, at the Pelican Island National Wildlife Refuge, at ORCA, in abandoned orange groves, and elsewhere.  Giant panicum is another common name for this grass, and Panicum maximum was a former scientific name.

Caesarweed (Urena lobata)

This plant is a horrible hitch-hiker.  After tiny pink hibiscus-type flowers, this plant has sticky burrs that get transported about on your clothes and the fur of animals.  When young, it is easy to pull out.  Do it, before the bad burrs arrive.

More invasives will come to Florida, and we need to keep everlastingly at it!

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