Ok, I guess I am an idiot still in this field. Seems clover (what I think this weed is), is a broad-leaf, so in theory it should be killed by FIESTA. Not sure what's going on here, but I guess it's due to the fact Clover lives over a year?

Clover is an annual and comes back from seed each year. There are a bunch of annual three-leaved look alikes and it is hard to tell from just the picture above. Any chance of a picture of the flower? Black medic (Medicago lupulina), Japanese clover (Kummerowia striata) and woodsorrel (Oxalis stricta) are just a few that have similar appearance but different flowers.

Fiesta is touted to be a "gentle" herbicide, one with which I have had no experience. Weed B Gon has worked for me on all the plants named but is apparently not as eco-friendly as Fiesta.

hortster

Looks similar to Yellow Wood Sorrel to me.

Here is a link that might be useful: Yellow Wood Sorrel

That grass looks so tall it's falling over. If so, if you can mow more often, the 'clover' can't make as many seeds.

It's impossible to id it precisely from that picture but it is not an OXalis. Can you do a closer view? The nearest I can think of is something like Black Medick, Medicago lupulina. it is absolutely NOT true that 'Clover is an annual'. There are many clovers and many of them are perennials including Trifolium repens, White Clover. They are all broad leaved so a BL herbicide should affect them. But as purple said - mowing would keep them in check too.

florauk, you have taught me something. You are correct in that white clover is a perennial. I have always believed that it was an annual from seed because: Long ago an old nurseryman told me that it would not return (I assumed from seed) if a heavy sulfur dust application was applied to the area. I did so in spring on a small patch in my back yard and it did not return the next year. Ever since I have thought that the sulfur prevented the seed from germinating, but it must have been that acidity prevented or killed the clover.
Spoke from an apparently flawed personal experience. Oops. Thanks for the awakening!

We don't know where taxtax is from but around here we have had a major influx of Japanese clover as mentioned above. It also looks very similar to the picture.

hortster

Hi hortster - I looked up Japanese clover and it had pinkish flowers. I thought the OP's picture looked as if it had small ball shaped yellowish flowers. Or maybe they are seed heads?

You are very likely correct. I perceived them as yellowing leaves at first glance at the fuzzy pic. They do appear to be the right shape for black medic.

hortster