Eradicating Invasive Four O'Clocks from the Garden

Four o'clocks (Mirabilis jalapa) have charmed Southern gardeners for over two centuries with their trumpet-shaped blooms in pink, yellow, and red that open in late afternoon. But their massive, tuberous roots and prolific self-seeding make them a nightmare once they escape a designated bed.

Why They're So Persistent

The plant forms large, sweet-potato-like tubers that store immense energy. Even if you snap off every stem, the tuber simply resprouts. Seeds scatter widely and germinate readily, creating new colonies. In most of Georgia, the roots are perennial, so the plant returns each spring with renewed vigor.

Effective Control Strategies

There is no easy spray-and-forget solution. The most reliable approach combines two tactics:

• Dig deeply to remove every tuber you can find. This is best done when the soil is moist and the plants are actively growing, so you can trace stems down to the root.
• Spot-treat emerging shoots with a systemic herbicide (such as glyphosate) each spring. Apply carefully to the foliage of young sprouts; the chemical will translocate to the tuber. Repeat as needed through the season.

Persistence over several years is usually required for complete eradication.