The house next to My Florida Backyard is vacant and no one is taking care of the yard, so it's a little haven for wildflowers and even interesting weeds these days. In a corner on the north side of the house, these cheery little yellow flowers have taken over in recent weeks.
We consulted the always-handy Wildflowers of Florida Field Guide and found our answer on pages 302-303: Oriental False Hawksbeard (Youngia japonica). As the species name would indicate, this is a non-native from Asia which has naturalized around the globe in the tropics and semi-tropics.
Gardeners often say that a weed is just a flower growing where it isn't wanted, but it seems no one has any love for hawksbeard. It's one of the most common pests encountered by those attempting to cultivate a nice green lawn in Florida (good luck with that, folks), and can be hard to get rid of; there's evidence of this plant beginning to show herbicide resistance in its native Japan. It doesn't seem to be bothered by frosts in our area, and the dandelion-like seeds spread quickly by wind from the multiple flower heads.
This plant is an annual with a shallow taproot, so if you find it growing where you don't want it, it's best to simply remove it by hand. If the heads have gone to seed, you can avoid spreading the seeds by snipping off the seed heads first and carefully placing them in your yard waste. Check the area in a week or two to see if new plants have sprouted from seed heads you missed, and remove them the same way.
On the plus side, this plant is seldom found in the wild and it doesn't appear to have a disrupting effect on native plants, so it's not considered a harmful invasive. It's mostly just a nuisance for those concerned with the perfect lawn (something My Florida Backyard will certainly never be). The rest of us will just live with it, maybe even enjoying the glimpse of happy yellow it adds to the landscape around us.