Veronica/speedwell is slowly taking hold in my yard. I've tried pulling it up but it's outpacing me. Seems every other day I pull up about a half-gallon's worth as measured by my weed bucket.
It's time to escalate. So far I've tried both Ortho Weed-B-Gone Max and Bayer Advanced All-In-One weedkiller using a pump sprayer. It seems like speedwell actually thrives on the Ortho spray. If I didn't know better, I'd guess that it contained fertilizer instead.
After several applications of the Bayer spray at the recommended concentration, the speedwell turns slightly yellow but the yellowed plants return to green if I go more than a week between sprays. On a whim, I poured about a tablespoon of Bayer at full strength on a small cluster of speedwell and it indeed killed it but I obviously cannot do this over the entire yard.
My question: what is available to homeowners that can effectively control this weed? I've read that dithiopyr and isoxaben are both effective but I haven't found anything at the local home center or farm store that contains them.