“I Can See Clearly Now” composer Johnny Nash sang in his 1972 hit. And WOW! What I see after last week’s five inches of rain is certainly clear but dishearteningly disturbing. Normally I’d be gleeful with a lot of blooming things this close to an upcoming BioBlitz;* unfortunately, the prevailing growth is that of invasive species.
Seemingly overnight, Kleberg bluestem and Guinea grasses shot up to nearly waist high. Even though I’d mowed the week prior to the recent rains, I had to barrage through the gate with the weed trimmer. In another part of the yard, the summer-neglected shrubbery along one of the fences revealed large clumps of Guinea grass over six feet tall and pop-up popinacs shooting through the snake eyes and fiddlewood shrubs.
With the ground still moist from the rains, it was time to tackle the invasive invaders.
Kleberg bluestem (Dichanthium annulatum) is an introduced grass native to southern Asia and North Africa, according to Texas A&M AgriLife Extension’s Plants of Texas Rangelands. It grows as a bunch grass with culms (hollow stems) from eight to 40 inches in length either prostrate or erect. It’s a fast grower, matures quickly, outcompetes native grasses and is a prolific seed producer that goes to seed in summer; seeds are rapidly transported by the wind. It is stoloniferous, which means the stems creep along the ground and root at the nodes, giving rise to new plants. Labeled an aggressive invader, it grows in any environment from dry to moist but offers poor nutrition to livestock or wildlife.
Guinea grass (Megathyrsus maximus) also is a bunch grass. It’s a perennial, native to Africa and Yemen. It has broad, long green leaves, densely tufted with many-branched whorled branchlets. The crown, or center near the soil, is reddish in color on younger plants. Many a Texas Master Naturalist is familiar with this grass, especially those who have cleared land prior to planting a native specialty garden.
New growth Guinea grass is relatively easy to pull out of the soil by hand. After a long hard summer drought, a sturdy garden fork may not even break the ground around the roots. But now, while the ground is moist, a well-built garden fork is useful. Jab the fork in the ground close to the base of the plant and shove it deep, forcing it with your foot and a hefty bit of muscle. Before repositioning the fork, push the handle toward the ground like you’re doing toe-touches, until you hear the roots begin to rip. Do this four times around the root mass, if you can get to it, and generally, after the fourth section, the large clump can be extracted. Shake off the soil and toss the debris in a pile to be removed. Do not use it in a compost pile, it’ll just revive and keep growing, blooming, going to seed and being scattered by the wind like the Kleberg bluestem.
The best thing to do if you’re inundated with either of these invasive grasses is to keep calm and mow on – don’t allow them to go to seed, if you can keep from it!
Equally horrifying was the discovery of non-native red center morning glory (Ipomoea Amnicola) shrouding many of the trees edging the resaca. The recent rains seem to have given the vines the impetus to bloom, which dramatically called attention to the spectacular invasive spectacle. While the green vines and leaves silently slithered through, around and over equally green flora, it wasn’t until the white flowers burst open that it called attention to its covert invasion.
Red center morning glory is an introduced plant native to Paraguay. Cameron, Hidalgo, Starr and Willacy counties can all be invaded with this species. The freeze of winter 2021 did not impair the proclivity of this vine. In fact, it seemed to spur it on as if that near death threat made it more determined to proliferate. Last fall, the vines had taken over a small hill at the back of our property, integrated and covered a large anacua tree and half of a mature Texas olive tree. I spent a considerable amount of time eradicating the vines from the grassy hill and pulling them out of the trees and off the plants in the marsh, as much as I was able to reach. This year, they are shrouding trees all around the resaca in unobtainable positions. The thousands of blooms are producing legions of seeds. It's scary; I fear for the future of the riparian forest. If you discover this pretty-but-treacherous flower in your yard, rip it out by the roots before it’s too late! And be judicious next spring with the mowing and weed edging to keep the vines at bay.
If all that wasn’t bad enough, a popinac (Leucaena leucocephla) shot up strong, healthy and double trunked this year, between a huisache and retama that I’d saved from the farmer’s bush-cutter last year at the edge of our property. Also called white leadtree, river tamarind and tan tan, popinac is a fast-growing invasive species introduced from tropical America. It is a prolific seed producer. Mature trees are prone to easily uproot in rain and wind, but you don’t want this species to mature.
A chain saw will have to take down the large popinac. New growth popinac can easily be cut off at ground level with clippers or loppers. Mark the stem stub with your clippers so you can easily find it. I keep full-strength liquid root and stump killer handy and paint the stub, using a cheap disposable small paint brush. After I take down the larger popinac tree, I’ll paint the stump three days in a row and ensure the poison is painted to the inner bark (phloem) and drips over the outer bark.
The popinac tree is pretty but dangerous to our native habitat. A close relative, tepeguaje (Leucaena pulverulenta), is one to consider, though. It’s native. Both trees have those creamy-white, sweet scented puffy balls of flowers and mimosa-lacy feathery foliage that bloom spring and summer and after a September rain. The legumes (fruit) are clumps of reddish, papery pods about 6 inches long. Both species have rapid growth; mature trees can reach upwards of 26 to 33 feet tall. The trees are thornless and have a broad crown that’s useful for nest sites, although the branches are weak and brittle.
There is an important distinguishing feature of these two trees: the narrow leaflets on the tepeguaje have little or no spaces between them, whereas the popinac leaflets are broader and have noticeable spaces between the leaflets, as in the photos above. A comparison is depicted on page 245 of the Richardson, A., King, K. book, “Plants of Deep South Texas,” Texas A&M University Press.
* 2022 Texas Pollinator BioBlitz – October 7 – 23, 2022 – Pollinators and the plants that rely on them. Sign into your iNaturalist.org account and join the project. https://www.inaturalist.org/projects/2022-texas-pollinator-bioblitz