Tuesday, December 12, 2017

Damn the Torpedograss!


       The native white-or-yellow-flowered Heliotropium polyphyllum and the lavender exotic Heliotropium amplexicaule make good groundcovers where foot traffic is light. They are popular with butterflies and other pollinators. They tend to die back in the dry season for me because I don't give them much water, and in really dry and windy stretches they may get attacked by whitefly. I cut them back hard a couple times a year to keep them looking good. Heliotropes are members of the borage family, and their old leaves turn black. If you don't cut them back periodically you end up with a thatch of dead leaves and bare stems with just some ratty foliage on top. They don't seem to compete well in my yard, so it takes occasional, but regular, weeding to maintain a nice patch.


Heliotropium polyphyllum
"Pineland Heliotrope"

This species also does well in coastal, sandy areas. I rescued mine from a vacant lot that was about to be developed.
     
       Some years ago I noticed some grass appearing in a patch of Heliotropiums in the back yard. Ignoring it turned out to be a huge mistake, because it soon was choking out everything in that small quadrant. 
            This was my introduction to  Panicum repens, aka “torpedograss,” “quack grass,” and “bullet grass.” Truly a weed from hell, this grass is a serious problem worldwide. It is native to parts of Asia and Africa. Though it grows from seeds, its main method of attack in Florida is by way of tough rhizomes (creeping underground horizontal stems), which can extend downward more than 2 feet. The rhizomes produce sharp stiff points – the “bullets” or “torpedoes” – that penetrate weed barriers and even thin paving. Any little piece of the rhizome can start a new plant. "My" torpedograss probably sneaked in from my neighbor, who didn't have a lawn, but just kept his weeds mowed to give an illusion of green. Turf grass doesn't do well in South Florida, so I'm not blaming him! He no doubt was "infected" by somebody else.

Panicum repens rhizome and parts of blades

            Torpedograss was around in the late 1800's, but became widespread with the help of the USDA, which reportedly imported and distributed seeds for planting in pastures in the 1920's. It's not    clear whether torpedograss even provides good forage.
            Now this serious pest of cropland, citrus groves and natural areas extends throughout Florida and along the Gulf Coast westward through Texas. It also occurs in Georgia, South and North Carolina, California and Hawaii. It tolerates just about any soil, growing both in dry sand and in the rich muck of swamps and lakes. It grows rampantly in warm weather, and slows down in the cooler months. The blades can grow 3 feet tall or more.
            The largest infestation in Florida is around Lake Okeechobee, where it has displaced at least 7,000 acres of native marsh. IFAS (University of Florida Institute of Food and Agricultural Sciences) estimates that it has invaded 70% of Florida's waters. It is especially insidious because it closely resembles, and grows alongside, the native  maidencane (Panicum hemitomon), a vital part of the natural ecosystem, making efforts to control it even more difficult. 
            The State of Florida spends millions of dollars a year on management of this pest. In the words of Dan Gill, garden columnist for the New Orleans Times-Picayune, "Torpedograss is not difficult to eradicate: It is nearly impossible to eradicate.”
            Glyphosate is the herbicide most recommended for chemical control. Repeated sprays at the highest label rates are required. There are problems with Glyphosate, though. It is  non-selective herbicide, meaning it kills anything, so any spray drift or drips can be lethal to plants you don't want to kill. 
             I literally painted individual stems and leaves of the grass with a pastry brush saturated with high-rate Glyphosate mix. (I wore gloves and protective clothing). Even though the area was small, this was time-consuming, back-and-knee-killing work. It had to be repeated, and it didn't eliminate the problem.  Even though I was careful, there was collateral damage, especially to a Florida native called gopher apple (Licania michauxii).  It's pure speculation on my part, but I wonder if there was some root-to-root, or soil-to-root transfer of the herbicide.

Licania michauxii
"Gopher Apple"



            After the initial kill I dug out as many rhizomes as I could. The stems are strong, and when pulled, may just break off at ground level. Any parts left underground merrily continue growing. I had to get down and dirty to get at the rhizomes – a delicate operation since they were intertwined with the roots of desirable plants, so no matter how careful I was, I still damaged the plants I was trying to save.  I was amazed at both how deep and how long the rhizomes extended. Every time I pulled out one a foot long or more, I felt like I'd bagged a "big one!"
            That was about 7 years ago. I no longer use Glyphosate, but just try to dig, clip, and pull. Given the amount of work it has taken to keep it under control in an area no bigger than  20’ x 20’at most,  the scope of the problem in Florida and the rest of the world is staggering. It would be nice if our nursery and agricultural agencies would learn to “just say no,” to imports sometimes.

Megachile (Alfalfa Bee) on Pineland Heliotrope


For more information on Torpedograss:


 Gill, Dan. “Go on the Offensive Against Torpedograss.” New Orleans Times-Picayune. July 19, 2012.


“Panicum repens L”. Langeland, Cherry et al. University of Fl.-IFAS Pub. Sp257. 2008. Center for Aquatic and Invasive Plants. University of Florida, IFAS. Also available through Florida Exotic Pest Plant Council.  www. Fleppc.org.


USDA Plants Database. Plants.usda.gov.


Yarlett, Lewis. L. Common Grasses of Florida and the Southeast. Florida Native Plant Society. 1996. P. 143.


Saturday, December 2, 2017

Strangler Fig

South Florida has its share of botanical oddities, and one of the strangest of these is the strangler fig, Ficus aurea Nutt. This plant occurs in the Bahamas, West Indies, and up into central Florida. It is a vitally important source of food for wildlife, especially birds. Often seen in swamps and sloughs, it also thrives just behind the dune line on beaches, and in general landscape conditions. Given time and space, the strangler fig becomes a magnificent tree, 50-60 feet tall, with a wide, rounded crown.


Berries and Leaves
Delnor Wiggins Pass State Park

The very name of the plant creates a little shiver, which its growth pattern does nothing to dispel. It generally starts out as an epiphyte, after a seed which has lodged in a rough spot in the bark of a tree or behind the "boot" of a cabbage palm germinates. (The "boot" is what is left after the rest of an old frond has fallen off the tree. It is actually the base of the frond, and creates a mini-habitat for all manner of flora and fauna).  After it germinates, the seed puts out  an aerial root, which  grows downward and around, vine-like, until it reaches the ground.

Strangler Fig beginning to grow on Cabbage Palm.
Cabbage Palm still thriving
Delnor Wiggins Pass State Park, 
Naples, FL



Once rooted, it starts growing back up and around the tree, gradually encircling and constricting its host. 



Strangler fig beginning to grow back up a cabbage palm
 Weaver's Station, Fakahatchee Strand State Preserve, Collier County Florida


As the stems/roots grow they sport numerous new aerial roots, so the process of encirclement accelerates after a certain point. Eventually all these vining stems may come together to form a trunk. Cabbage palms typically die when their crowns are shaded out, or even collapse under the fig's weight. Hardwoods die as the circulation of water and nutrients is increasingly restricted.




Strangler Fig and dead Cabbage Palm
Delnor Wiggins Pass State Park
Naples, Florida



The battle between the strangler fig and huge cypress trees can be epic, taking decades to be won, or ending in a standoff. The strain is visible as the bark of the cypress breaks and buckles within the fig's coils. Even an apparently moribund cypress will still send out shoots and sprouts its bid to survive.




Strangler Fig and Bald Cypress
Big Cypress Boardwalk
Fakahatchee Strand


The texture of an old fig is like the proverbial moonscape, with warts, bumps, ripples and dents, and often is decorated with moss, algae and/or lichens.


Strangler Fig on Bald Cypress
Fakahatchee Strand
Big Cypress Bend Boardwalk





Back in the 1950's my young friends and I were completely unfazed by the profusion of deadly toxic oleanders in the Florida landscape. They even were planted on the grounds of our elementary school, and we played in their shade. We knew better than to mess with them, and we liked the flowers. Strangler figs were another matter altogether. Shivering in delighted horror, we shared tales of unfortunates who went to sleep in the shade of a strangler fig, only to awaken, too late! in its suffocating coils. Even as an adult who is not afraid of snakes, I still find something a little macabre, inexorable and python-like about this plant.




Strangler Fig and Spanish Moss on
Cabbage Palm
Rookery Bay National Estuarine Research Reserve
Collier County, FL