This is for all you DIY folks that want to know what the professionals would do.

Shoutout to Urban Earth in Midtown Memphis, TN, and Germantown Hardware in Germantown, TN.

Pre emergents create a barrier in the soil at the level where weed seeds germinate that prevent seeds from developing. Pre emergents do not simply kill seeds — the product must be present at the time germination happens. One way to tell when soil temperatures are nearing 55 degrees is when the forsythia bushes start to bloom.

Pre emergents do not stop weeds coming up from the roots of a plant that has previously emerged (perennial weeds).

Common Pre-Emergent Products

Simazine / Atrazine

Short-lived, about 60 days. Not the stand-alone choice for Memphis lawns. Not safe for cool-season grasses like fescue or rye.

Pendimethalin (Pendulum)

Shorter term, starts to break down after 40 days and is gone around 80 days. Good transitional pre-emergent.

Dithiopyr (Dimension)

Longer residual of 4 months. Also has some post-emergent capabilities — will kill immature crabgrass shortly after it emerges.

Prodiamine (Barricade or Stonewall)

One of the longer effective periods in the soil, up to 9 months at maximum rates. Available in liquid and granular. Apply before or right after soil temperatures hit 55°F.

In summary, Simazine, Atrazine, and pendimethalin are fine in the fall or early spring. Dithiopyr is a solid middle-ground. The best stand-alone pre-emergent for the money is probably Prodiamine given the price and longevity.

Important: Read the label and apply according to label rates. Pre-emergents need to be cycled out every two to three years to avoid weed resistance.