CRABGRASS | FORSYTHIA BLOOMING | PRE-EMERGENT

For years, homeowners and lawn pros alike relied on one simple rule: “When the forsythia blooms, it’s time to put down pre-emergent. ”While that used to be the golden standard, lawn care has evolved—and so have the products we use. With today’s advanced pre-emergents, you don’t have to panic if you miss the first bloom. Here's what you need to know about crabgrass, forsythia, and the real window for weed prevention.

🌿 What Is Crabgrass and Why Do We Fight It?

Crabgrass is an aggressive summer annual weed that thrives in bare, sunny spots. It germinates in the spring and spreads quickly through heat and drought, choking out healthy grass and leaving your lawn looking patchy and worn down.

The key to controlling crabgrass is stopping it before it emerges—which is where pre-emergent herbicides come in.

🌼 Forsythia: The Old Signal for Spring Weed Control

Forsythia shrubs, with their bright yellow blooms, were once a trusted signal for crabgrass prevention. The logic? Forsythia flowers start to bloom when soil temperatures hit 50–55°F—the same temps that crabgrass starts to germinate.

So, the idea was: apply pre-emergent when forsythia blooms, or you’ll miss the window.

But that’s old-school thinking.

🚫 Why That Rule Is Outdated

Thanks to newer and longer-lasting pre-emergents, we now have a broader and more flexible application window. These modern formulas:

• Stay active in the soil longer

• Provide season-long crabgrass control when timed properly

• Can still be effective when applied in mid-to-late spring

That means if your forsythia is already dropping petals—you still have time.

In fact, some pre-emergents like dithiopyr even offer early post-emergent control, which can knock out young crabgrass plants that have just started growing.