Little Daisy - Big Problem

A year or so ago I noticed a sprawling, low-growing aster relative cropping up here and there in the yard. I found it completely undistinguished and entirely without ornamental value, but I didn't make more than a half-hearted effort to get rid of it.

Like so many uninvited visitors, it has proven itself a very unwelcome guest in no hurry to leave. It has been beastly hot much of this summer, and I haven't been working in the yard as much as usual. I walked outside a few weeks back and discovered that this seemingly unassuming plant was in the process of overrunning the yard.

A quick ID session revealed it to be Tridax procumbens, or "coat buttons," a noxious weed if ever there were one. Originating in Central America, it has spread worldwide, and infests just about any location with a mild climate. It appears that the only places the weed has established itself in the United States are Florida, Puerto Rico ( I know it's a territory, not a state) and Hawaii, though there have been sporadic outbreaks in other states. However, if it is in north Florida and the Florida panhandle, it must be creeping into southern Georgia and Alabama by now.

Tridax procumbens, habit, ray floret, head

Tridax procumbens has opposite leaves which are arrow-shaped and deeply toothed. The margins (leaf edges) are fringed with tiny hairs. The top surface is felty dark green, with deeply impressed veins. If you bend a leaf to catch the light you will see glittering ranks of  short, stiff hairs that create a texture like fine-grit sandpaper.

The undersides of the leaves are a paler, grayish green with a less scabrous texture. The raised veins are very pronounced, and sport hairs of varying lengths.

The entire plant - leaves, petioles, stems, bases of the flower heads - is hairy. The stems are pale green shading into magenta-brown. The entire head is no bigger than a dime. It has numerous yellow disc flowers and a rather sparing ring of off-white or cream-colored ray florets ending in 3 teeth. (Hence the name "Tridax"). The heads produce thousands of achenes (seeds) whose chaff lets them float away on any breeze.

Leaves, Stems, Heads, Bristles

Triadax procumbens is on the Federal Noxious Weed List as well as the Noxious Weed List of the Florida Department of Agriculture and Consumer Services. It is also on Florida's Prohibited Aquatic and Wetland Plants List. My yard is dry and sandy, but the plant evidently thrives even more given moist conditions.

It's not altogether easy to weed, especially when it is intertwined with groundcovers. It's hard sometimes to find the central point from which the stems radiate outward, especially since the stems are brittle and break easily. You've got to get the taproot, though, or the thing will just regenerate.

In Florida it is illegal to possess, transport or sell "coat buttons." I don't know whether having an infestation on your property qualifies as "possession," but I wanted to be rid of it in any case. I bagged it and disposed of it in the garbage, not the yard waste. Better buried in the landfill than further distributed in county mulch. Though I've won the first round, I am sure I am not through with the war. There must be an established seed bank in the yard by now, and the source of the original contamination likely is still churning out the achenes.

Noxious or not, the plant has medicinal and pest-fighting qualities. It is used in indigenous medicine for a variety of ailments, including wound treatment, stopping bleeding, diarrhea, backache, bronchial congestion, and worms. Dried pulerized leaves and essential oils extracted from the leaves appear to provide some control against insects, nematodes and fungi. Though not native to India, it is used in Ayurvedic medicine. It also has cancer-fighting potential.

Emilia fosbergii - Weeds I Like

Since I've been fulminating against weeds, I thought I'd mention some of the ones I like. One of them is Emilia fosbergii, or "Florida Tasselflower." Since there's no grass to compete against, it comes up everywhere in the yard, but it is easy to pull, so I leave it where I like it, and pull out the rest. (Or not. I am a lazy gardener).The ones that  haven't yet gone to seed go into the compost pot. Pollinators like it too.

The top and the bottom of Emilia sort of don't match. Tall, thin stalks end in delicate nodding, drooping, sometimes upright heads of rose-red disc flowers(more on this later). The anthers (pollen-bearing structures) and pollen are bright orange-yellow. The heads are around a half-inch long or a little more, depending on where the plant is growing, and about a quarter-inch wide at the base. The bottom of the plant on the other hand, is robust and vigorous.

Vigorous Bottom Portion of Plant

The stems and new leaves can be intensely hairy. Older leaves and "sepals" (phyllaries) show varying degrees of hairiness. The way the heads seem just to float above the foliage would make Emilia a nice plant to include in a mixed border. A larger plant with 8-10 flowering stems could even have the honor of a place in front, but since Tasselflower is a weed, its growth can be unpredictable. The flowering heads can be anywhere from 4 -to - 6 inches above the ground in young plants, up to around 20 inches above ground on older, larger plants. Growing conditions also affect the size and number of flowering stalks. The plants deteriorate after they set seeds. I haven't tried dead-heading to see whether I could prolong blooming, because the plant self-sows so vigorously.


The growth form of the plant is pretty cool. The first leaves on the stem are quite different from those farther along. They are roughly the shape of an inverted triangle on a long thin stem. The "stem" is actually not a petiole, but an extremely narrowed part of the leaf blade itself. As you move up the plant you get  intermediate leaf stages with increasingly shortened "stalks." The leaf itself becomes more oblong, and eventually arrow-shaped. At first glance it looks like the stem punches through the higher-up leaves, but a closer look shows that the base of the leaf clasps the stem.

Another leaf clasping a stem is formed between the "old" leaf and the main stem. This smaller leaf gradually enlarges to full size as the stem new itself grows longer. In the drawing below you can see the tiny leaf just to the right of the caption. The new stem elongates while the leaf enlarges, until you get the structure in the right hand of the drawing, in which the leaf and stem appear "on top" of the older leaf.

Another species, Emilia sonchifolia, "Lilac Tasselflower," occurs much less frequently in the yard. In general it seems a more diminutive and less vigorous plant, but that may be a function of its environment. The disk florets are a beautiful purple-pink instead of red. It is less common than its red cousin. According to the USDA Plants Database website, Emilia fosbergii occurs in Florida, Georgia, Louisiana, Texas and California. Its origin is unclear, with Asia, Australia, and South and Central America all listed as possibilities.


Emilia is a member of the Aster family. What many people (and I used to be among them) think of as a single flower in this family is actually a conglomeration, or composite, of individual flowers or florets, called a "head." This might seem like a trick the botanists have come up with to  keep us amateurs out, but it actually makes sense once you start really looking hard. The things that look like petals are "ray florets," and the things in the middle are "disk florets." The first drawing, on the left, shows the entire head, with ray florets around the outside, and the disk in the center. The drawing on the far right shows a cross section of the disk, with opened disk florets near the outside of the circle, and unopened disk flowers near the center. I gather, and I may be wrong, wrong, wrong, that in a case like the one illustrated, the ray florets are sterile, while the disk florets are fertile.

Pityopsis graminifolia
"Narrow leaf Silk Grass"

To make things more complicated, some members of the Aster family have only ray flowers. In this case they are fertile, and they are called ligulate florets. Ligulate florets have teeth. In the drawing of Hieracium megacephalon, "Hawkweed," below, there is no central disk, only ligulate florets. The sexual parts of the florets emerge from the base, so are clustered in the center of the head. Notice the teeth.

Hieracium megacephalon
Coastal Plain Hawkweed

And, there are members of the family with only disk florets, like Emilia, Ageratum, or thistles.

Circium, sp. "Thistle"

I find the seemingly infinite variety of ways in which plants go about their business utterly fascinating, and I keep discovering new things every time I look hard even at familiar plants.