It's hard to choose only five weeds that we hate but these five invasive species are particularly noxious, especially in the fall when they bloom and spread. Trying to have a flower garden in Florida's fall? You'll more than likely encounter these invasive species.
# 1 Murdannia keisak
Marsh Dewflower
Number one on my list of worst weeds is Murdannia keisak best known as the "wart-removing weed" or "marsh dewflower." This weed looks and behaves a lot like Florida Dayflower (Commelina diffusa) another introduced invasive species, but Murdannia keisak has proved too adaptable for dayflower and now completely outcompetes the more familiar invader (Dayflower remains a very annoying pest wherever it occurs).
Introduced from China, like so many of our weeds, the plant is associated with rice growing in East Asia. It has found living on Florida sandhills to be quite acceptable as well.
Murdannia keisak forms dense root mats and eradicating it also eradicates a layer of topsoil which is in very short supply atop Florida sandhills. When the weather is dry the plant immediately seeds. Its roots are so thick it is nearly impossible to remove from dry soil.
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When stressed by heat or dry the plant immediately flowers and fruits. The fruit is a capsule with several small seeds.
The first record of this plant occuring in the United States was in the 1920s Louisiana followed by reports of the plant in South Carolina in the 1930s. Only in recent decades has it colonized Central Florida, likely brought in through the commercial plant trade.
#2 Oplismenus
Basketgrass
Number two on my list of worst Florida weeds is Basketgrass (Oplismenus spp.). Many species of Oplismenus grow in Central Florida. Oplismenus setarius is a native perennial while Oplismenus hirtellus (the more common species) is an invasive species. Both species are troublesome, to say the least.
In shady areas of the landscape Basketgrass is particularly problematic. In the shade, once established, it is nearly impossible to eradicate. Basketgrass requires little to no irrigation or maintenance and creates dense mats where it occurs.
Even in stone walkways basketgrass is able to establish itself. Below a stand of Oplimenus hirtellus takes off in, well, granite gravel with no soil around.
In your Central Florida garden you likely have Oplimenus hirtellus but you could also have Oplimenus burmannii or Oplismenus setarius or other Oplimenus species.
#3 Eragrostis minor
Little Love Grass
Also known as Little Love Grass, Eragrostis minor is a new and particularly annoying weed in my gardens. From my experience it is almost impossible to eradicate by hand. The plant is so well rooted that when you pull it the seeds and leave break off leaving a viable stem behind.
Little love grass took a different route than many of our invasive weeds in Florida. It came from Europe.
I find troweling works best with this weed and knowing that you will never get it all. The grass tends to grow in tufts so there are groups of plants together. Try and get them all before they seed. Seeding can occur when new plants are only weeks old.
# 4 Phyllanthus urinaria
Chamber Bitter
Chamber biter (Phyllanthus urinaria) used to be one of the most hated weeds in Florida but it has been overtaken and outcompeted by the weeds listed above. Still, where it occurs chamber bitter can be really annoying.
Chamber bitter is another Asian invasive species that is naturalized across the Southern USA. In Asia it is cultivated as a Chinese herbal medicine. In Florida, it is a worthless invasive weed that is less difficult to remove than others but produces so many seed that once established you'll be spending me mornings and afternoons trying to get it all.
Chamber bitter seed are a distinctive round fruit that are borne on the undersides of the lateral branches at the leaf axils. Similar in appearance to the long-stalked phyllanthus (Phyllanthus tenellus; we have both in Florida), the two species differ by the length of the seedpod stalks. Chamber bitter seed are borne sessile (without stalks) whereas long-stalked phyllanthus seed are up to 1/2 inch long.
The best way to manage Phyllanthus urinaria is to not let it go to seed. Pull out the young plants as soon as you see them. A one month old plant (above and below) produce hundreds of viable seed.
Note that Chamber bitter is highly toxic and produces an irritating juice after injury. These juices may irritate the skin or eyes. Wear gloves when pulling any of these weeds even thought it might be easier to weed bare-handed.
#5 Drymaria cordata
Tropical Chickweed
Above, a dense mat of Tropical Chickweed, hosting a coral snake. Look closely, the native snake is quite at home in this definitely non-native weed species.
Also known as West Indian Chickweed, or Sticky Weed this invasive herbaceous annual in the Pink family (Caryophyllaceae) is a Mexican native. It is also found in the West Indies and Central and South America.
Unlike the other weeds featured on this page Sticky Weed produces a taproot making it unlikely that you'll ever eradicate it from your garden. The foliage sticks to your hands or gloves while the root holds firm.
The stems are prostrate, green in color, glabrous to glandular pubescent, and root at some nodes. Leaves are petiolate, opposite, orbicular to reniform in outline, entire, and glabrous.
Above the Tropical Chickweed is being outcompeted by Marsh Dewflower, below the Tropical Chickweed tries to compete with Basketgrass.
One good thing about the Tropical Chickweed. It is entire edible. So, I know where you could get enough for a few hundred big salads.
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