What pre-emergent do I need to apply in the fall for dandelions, henbit, and poa annua? I know I need to use dimension or amaze for spring weeds like crabgrass, but not sure about fall/winter weeds. Would I use the same thing?
The fall preemergent is really only affective for winter annuals like poa annua. I think more important than what you use, is when you apply it. Poa annua germinates when soil temps drop below 70 degrees. It's better to be a little early, than a little late for the late summer/fall drop. Most of the preemergents do a good job, but it might be a good idea to pick one that lasts the longest to prevent any poa annua germination. Dimension lasts 120 days (according to the brochure) and I think Halts lasts 60-90 days. Barricade can last from 90-240 days depending on application rates, so technically you could be protected for 8 months, but I would probably just apply enough for 6 months, and reapply in the spring.
Well that doesn't really answer my question at all. I already know about timing and all. I just want to know specific brands that control winter or fall weed seeds. Maybe Texas Weed can chime in.
Most preemergents are non-selective. The three I listed will prevent most weed seeds from germinating. Go with Dimension or Barricade.