Weeds, by definition, are unwanted in the garden. But gardeners know that some weeds are more unwanted than others. And still others are serial offenders that can only be described as most unwanted.
These last are pernicious weeds that excel at seed production, churning out massive quantities yearly. Many of those seeds stay viable in the soil for years, even decades, lying in wait for a flash of sunlight to spark them to life. This underground stockpile is called a “seed bank” (new weeds put away for a sunny day). In a typical home garden, the numbers can be staggering, with millions of seedy characters lying in wait to burst into weed.
For those who police home gardens, these weed seed statistics can be alarming. But statistics don’t tell the whole story. The well-armed gardener can take down these dormant bad boys, as seeds, before they grow into tough weeds. No weeds. No weeding.
Tracking The 10 Most Unwanted Weeds
To help gardeners get a grip on ten of the most frustrating, seed-producing garden weeds, Preen has created a series of “Most Unwanted Tip Sheets.” Modeled after the FBI’s classic “Most Wanted” campaigns, each tip sheet features mug shots, descriptions, identifying marks, and control notes. Everything needed and more to make a citizen’s arrest on seedy characters like these. The tip sheets are available from www.mostunwantedweeds.com.
This is something the makers of Preen know about: Preen pre-emergent products stop garden weeds from growing for up to three to six months per application by interrupting the seeds’ rooting. This keeps new weeds from growing, plus helps to deplete the seed bank’s reserves over time.
Following are excerpts from the "Most Unwanted Weed" tip sheets, with notes that indicate seed bank strengths for ten terrible garden thugs:
*Bindweed (Convolvulus arvensis) – Gets its street name for its habit of twining itself around other plants or anything else nearby. Its taproot can grow a whopping 10 feet deep, with lateral roots that can spread out 30 feet. Produces 30 to 300 seeds per plant per season. Seeds are viable for up to 50 years;
Chickweed, common (Stellaria media) – A petite but vigorous weed that grows densely, low to the ground, often creating a thick springy green mat. Produces up to 15,000 seeds, viable for decades;
Crabgrass, hairy (Digitaria sanguinalis) – Aggressive and difficult to eradicate, crabgrass spreads by seeds and also by stem nodes that can root and produce new stems wherever a stem touches soil. It thrives in hot moist conditions. Drought hardly fazes it. It produces up to 150,000 seeds, viable for three years.
Dandelion (Taraxacum officinale) – Its taproot is difficult to pull and its plumed seeds ride the wind. Classic dandelion puffballs each deliver 50 to 170 seeds, which can stay aloft on a four-mph breeze. One plant yields up to 15,000 seeds per season. Just one acre infested with dandelions can launch more than 240 million airborne seeds per year. Viable up to five years;
Lambsquarters, common (Chenopodium album) – Incredibly adaptable, it’s a nuisance in gardens as far north as Greenland. Produces up to 72,000 seeds, viable for 20 years or more;
Pigweed, redroot (Amaranthus retroflexus) – Grows so quickly and uses water so efficiently it muscles out bedmates. Typically produces up to 150,000 seeds. Hyper-achievers allegedly pump out nearly one million per plant per year. Viable for 10 years or more;
Plantain (Plantago major) – Its dense clumps compete with existing plants. Produces up to 20,000 seeds, and can re-grow from root crowns. Viable up to 60 years;
Purslane, common (Portulaca oleracea) – Difficult to eradicate once established, it can quickly overwhelm a garden or landscape bed. It spreads rapidly by seed and re-roots from loose bits when pulled or dug out. Produces up to 240,000 seeds, viable 30 to 40 years;
Spotted Spurge (Chamaesyce maculata) – Its central taproot can grow to two-feet deep. A thick milky sap oozes from broken stems and leaves. Beware: the sap is caustic and can cause severe, painful inflammation and blistering to skin, mouth, nose and eyes. It can be toxic to animals and harbor stinging ants. One plant produces up to 3,000 seeds. Viable for years, the exact duration unknown;
Woodsorrel, creeping (Oxalis corniculata) – Competitive and aggressive, it engages in "seed warfare,” as mature pods rupture to spew seeds up to 10 feet away. Produces up to 5,000 seeds, scientists don't yet know the seed lifespan.