Prostrate Knotweed

What’s blooming in the area behind the walls and fences: Hybrid tea roses, bird of paradise, silver lace vine, Japanese honeysuckle, trumpet creeper, Heavenly Blue morning glories nearly gone, sweet pea flourishing, Sensation cosmos, French marigolds, Maximilian sunflower; green pepper roasting done for year.

Outside the fences: Apache plume, leather-leaf globemallow, velvetweed, yellow evening primrose, datura, bindweed, scarlet creeper, ivy-leaf morning glory, older pigweed turning brown, ragweed, Russian thistle, goats’ head, chamisa, snakeweed, goat’s beard, horseweed, áñil del muerto, native sunflowers, gumweed, broom senecio, spiny lettuce, Tahokia daisy, purple, heath and golden hairy asters; milkweed leaves turning yellow, toothed spurge turning maroon.

In my yard looking north: Nasturtium, chocolate flower, blanket flower, Mexican hat, black-eyed Susan, yellow cosmos, chrysanthemum, Crackerjack marigold.

Looking east: Floribunda roses, hollyhock, winecup, large-leaf soapwort, scarlet flax, reseeded and Crimson Glory morning glories, pink evening primrose, zinnias; Autumn Joy sedum leaves losing color.

Looking south: Blaze, floribunda and miniature roses, cypress vine.

Looking west: Russian sage, catmint, lady bells, individual David phlox flowers, calamintha, sheltered purple coneflower, Mönch aster.

Bedding plants: Moss rose, snapdragon, nicotiana, sweet alyssum back.

Inside: Aptenia, asparagus fern, pomegranate.

Animal sightings: Rabbit, monarch butterfly, wasps, black harvester and small red ants.

Weather: Rain Tuesday night; short thunderstorm Friday morning; temperatures in high 30's yesterday morning; 11:29 hours of daylight today.

Weekly update: Prostrate knotweed is one of those weeds that survive because it’s no where near as noxious as its peers. It’s not poisonous, doesn’t have thorns, and doesn’t take over the best watered soil - it’s just not worth the same effort I expend to control pigweed and Siberian elms.

The dark brown seeds lie buried just beneath the surface in winter when cool temperatures and dampness revoke their dormancy, leaving them ready to germinate when conditions improve. They say the annuals first appear looking like grass, but I never notice them until a few stems a couple inches long appear with their rounded, oval leaves spaced too far apart to cover the soil.

This summer I was removing the white taproots from the zinnia bed when I was preparing it for seed in late May. Those early plants probably had four sets of chromosomes and peaked early, before the summer heat reintroduced dormancy in unsprouted seeds and sent everything else into remission.

Come the monsoons, enough moisture penetrates the warm soil for a second wave to grow, this time the ones with six sets of chromosomes. When I went out to weed in late July, I saw plants had returned in the zinnia bed and new ones were growing along the nearby fence. I haphazardly pulled some, but left many in my pursuit of other enemies.

Then, as seems to happen every year, events overtook my resolutions and things were left to grow as they would in late summer. When I went out last weekend, the knotweeds in the zinnia bed were turning brown, while the light-green ones in the shade of the fence had grow erect and lacy.

Out in the drive, in front of the garage, the thick doilies I first noted the middle of August had waxed fat, with thick blue-green leaves, some with red lines. At the leaf joints, small stems held clusters of dark rose buds, maybe a sixteenth of an inch across. Some were parting to expose their stamens, while others remain closed, shaking the pollen within to fertilize themselves.

Useful as a capacity to waste no resources on petals to attract insects or variations in chromosome counts may be to survival, I suspect an ability pass unnoticed has been more important.

No one knows where Polygonum aviculare emerged, but its fossilized seeds have been found in northern European strata dated to the Cromerian warming period during the middle ice age between 866,000 and 478,000 years ago. Jonathan Sauer believes they were "native pioneers preadapted to join in the migrations of early humans as ruderal camp followers."

With the appearance of neolithic farmers, the ground hugging plant moved into the fields from central Germany northwest to Britain. Either weeds weren’t yet seen as problems, or the red stems were tolerated.

By the time iron age people were sacrificing a man at Thor’s Grove in Jutland around 400bc, the seeds were part of the Tollund grainery, included in the gruel of his last meal. Another member of the buckwheat family, Persicaria lapathifolia, seems to have been gathered deliberately, but archaeologists debate if the inclusion of prostate knotweed was accidental or intentional.

Some 700 years later and eleven miles to the east, another man was sacrificed who’s body was found near Grauballe in 1954. His last meal contained fragments of 63 grains, including prostrate knotweed, but no spring greens or late summer fruits. From that, Peter Glob has argued he probably was killed in some late winter ritual designed to speed the arrival of spring.

The late season food fed to both men was relatively dirty, filled with hairs and ergot, a fungus that infects one of their main crops, rye. The Graballe man’s skeleton showed signs of near starvation when he was young and recent calcium deficiencies. It may be he died in a year when food supplies were particularly low, and everything non-toxic was eaten. Glob indicated the condition of his teeth showed this wasn’t his usual fare.

Prostrate knotweed moved to the compacted pathways when it was ejected by more fastidious farmers and traveled west with the first settlers to New England where John Josselyn reported in 1672 that knot grass had "sprung up since the English planted and kept cattle in New-England."

It continued moving west, annoying people who wanted perfect lawns, but otherwise dispersing by seed or contaminated nursery pots. A century ago it was considered "a common dooryard weed at middle levels in the mountains" of New Mexico.

Sometimes, people who confronted it as a new plant would test it: the Chinese tried it as a dye, the Ramah Navajo used a warm infusion to treat stomach aches. In the late nineteenth century, there was a brief fad for Hemero Tea to treat asthma and bronchitis in Austria and Germany.

But as usually happens with familiarity, most soon learned to ignore it.

In oblivion there is success for the meek.

Notes:Coward, Fiona, Stephen Shennan, Sue Colledge, James Conolly, and Mark Collard. "The Spread of Neotlithic Plant Economies from the Near East to Northwest Europe: A Phylogenetic Analysis, Journal of Archaeological Science 35:42-56:2008.

Glob. Peter Vilhelm. The Bog People: Iron-Age Man Preserved, 2004.

Josselyn, John. New England’s Rarities Discovered in Birds, Beasts, Fishes, Serpents and Plants of That Country, 1672, reprinted by University of Michigan, University Library with 1865 notes by Edward Tuckerman.

Meerts, Pierre. "An Experimental Investigation of Life History and Plasticity in Two Cytotypes of Polygonum aviculare L. Subsp. aviculare That Coexist in an Abandoned Arable Field, Oecologia 92:442-449:1992; on chromosomes.

Rafinesque, C. S. Medical Flora, volume 2, 1830; on China

Sauer, Jonathan D. Plant Migration: The Dynamics of Geographic Patterning in Seed Plant Species, 1988

Taylor, Timothy. The Buried Soul: How Humans Invented Death, 2004; on ergot.

Uphof, J. C. T. Dictionary of Economic Plants, 1968 edition; on Hemero Tea.

Vestal, Paul A. The Ethnobotany of the Ramah Navaho, 1952.

Wooten, Elmer Otis and Paul Carpenter Standley. Flora of New Mexico, 1915.

Photograph: Prostate knotweed, much enlarged, in my drive, 3 October 2010.