NC State Extension Publications

How Often Are You Weeding? Is It Frequently Enough to Prevent the Next Generation of Weeds?

Many of the most common weeds of container nurseries flower and produce seeds within 30 days. Our research suggests that you should be removing emerged weeds every 2 to 3 weeks. This prevents rapid population growth and spread, and can reduce hand weeding labor labor costs by around 40%. For more information on reducing your weed control costs check out the information on Cost Effective Weed Control in Container Nurseries.

These photos are of 6-week old weeds in containers and illustrate how rapidly many common nursery weeds reach reproductive maturity.

Spotted Spurge - Our Most Common Summer Weed

Spotted spurge can produce flowers within 21 days after seeding, and in another 10 days will have mature seed pods ready to begin the next generation. Additionally, spotted spurge seeds are forcefully expelled several feet from the mother plant.

spotted spurge plant fully covers a 4-liter pot

Six-week old spotted spurge.

J. Neal  CC BY-SA - 4.0

leafy stem with mature seed pods

Spotted spurge fruiting stem.

J. Neal  CC BY-NC - 4.0

Bittercress - Our Most Common Cool-Season Weed in Containers

Similarly, bittercress can flower and fruit within 30 days. Each plant producing more than 5,000 seeds and “shooting” the seeds 4 to 6 feet away to infest nearby crops. In this way, not only does bittercress spread rapidly in container nurseries, but populations rapidly increase.

bittercress plants fill pots with many fruiting stalks

Six-week old bittercress.

J. Neal  CC BY-ND - 4.0

bittercress fruit stalk, branched with slender seed pods

Bittercress seed pods (=siliques).

J. Neal  CC BY-ND - 4.0

Longstalked Phyllanthus Takes a Bit Longer to Reproduce

Longstalked phyllanthus is a common warm-season annual weed in container production. This species can flower within 30 days and will have mature seed pods within six weeks. You have a bit more time to remove this weed than you do for spurge or bittercress, but don't get complacent. Phyllanthus is not well controlled by many of our commonly used herbicides. It also can forcefully expel its seeds 4 to 6 feet from the mother plant.

upright stems, ~12 inches tall, lateral branches, oval leaves

Six-week old longstalked phyllanthus.

J. Neal  CC BY-ND - 4.0

mature branch, seed pods on 1-cm long stalks

Longstalked phyllanthus seed pods.

J. Neal  CC BY-ND - 4.0

What Can You Do About It?

Sanitation is a critical component of any weed management plan. Removing weeds before they can go to seed will pay dividends in the future by reducing the seedbank, limiting the spread of weeds, and making future weed control efforts more effective and less costly. Check out our information on nursery sanitation practices for weed control and reducing weed populations and spread in your nursery.

Author

Professor of Weed Science, Extension Specialist & Department Extension Leader
Horticultural Science

Publication date: Oct. 15, 2018

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