Are your weeds Cool Season Weeds or Warm Season Weeds? Annual or Perennial? Pre-emergents are only effective on annual weeds.  There are two categories of weeds based on how long they live. “Annual” weeds germinate, grow and complete their life cycles in one of their growing seasons. “Perennial” weeds come back from roots – that is, the same plant survives from one growing season to the next. Pre-emergents are only effective on annual weeds.

 The weeds you’re seeing out in your lawn right now are almost all annual weeds.

Grassburs and crabgrass prevention begins two weeks prior to average date of last killing freeze. See details in story.

• Pre-emergent means “before” something emerges. In this case, it means before it germinates, or sprouts. That’s important when you’re dealing with annual weeds.

For the weeds you can see now… Those are cool-season weeds that germinate in fall, so that application must be made the last week of August through the first week of September. Dimension, Halts or Balan for grassy weeds. Gallery for broadleafed weeds.

For the weeds that will germinate as it gets warmer… In most parts of Texas we’re worried mainly about crabgrass and grassburs. Those are summer weeds. Your first application needs to be about two weeks before the average date of your last killing freeze in your area. Learn that date and commit it to memory, because it’s one that will keep coming up for many gardening tasks. For those grassy weeds, apply Dimension, Halts or Balan.

Repeat the spring application 90 days later… These pre-emergents have a 100-day effective life, so you’ll need a booster shot three months after the first application. That will give you a full season of prevention against crabgrass and grassburs. We usually don’t have enough broadleafed weeds in the summer to justify the expense of Gallery granules.