Hoary Cress

What’s blooming in the area: Snow that covered everything receded yesterday afternoon. Someone must have had a sale on those propane-powered flame weeders; last weekend, at least four men had them strapped to dollies and were pacing their fields and yards to burn off dead vegetation. Village ditch meetings yesterday and today.

What’s blooming in my yard: Peach, forsythia and hyacinth flowers dead; yesterday icicles were dripping off roses and cholla; Siberian elm seedling unfazed.

Inside: Brazilian bougainvillea, South African aptenia, kalanchoë and rochea weed.

Animal sightings: Rabbit tracks Friday morning; some flies hatched; five head of cattle were brought to graze a fallow field near the village.

Weather: Thursday night rain began before sunset. Then temperatures dropped. Several inches of snow fell on layers of ice that broke branches along the main road and bent pines, Siberian elms and my largest spirea and rose of Sharon. Friday, enough ice melted for the shrubs to spring back, but Saturday morning the thermometer on my front porch read 18 degrees. It’s still March with 12:46 hours of daylight today.

Weekly update: Every spring since I’ve lived here, some short spikes with white heads have bloomed near the post office in April and May. This year, they bolted sooner.

Since I didn’t recognize them from my Michigan childhood, I simply called them the white head. When I looked them up, I discovered hoary cress is new to most people: its most common name is white top.

It’s not that it’s some exotic from the far Altai. Linnaeus knew it as Lepidium draba in 1753, and various people reported it in this country in the nineteenth century. It’s simply that Cardaria draba, as it’s sometimes known, didn’t become a pest until the twentieth century, long after the vocabulary for common plants was formed.

Hoary cress owes its fluorescence to people’s desire to farm the northern great plains. In 1895, a senator from Wyoming, Joseph Carey, sponsored legislation that allowed private companies to build irrigation systems to make public lands more desirable for homesteading. The act defined desert lands as those that couldn’t produce hay, and was particularly popular in Idaho and Wyoming.

A few years later, Congress allowed the agriculture department to send people to collect foreign seeds and prepare them for use in this country. In 1897, Niels Hansen left South Dakota to prospect for alfalfa in Turkestan. His hay seed was so successful in the frigid winter of 1898-1899, that he returned in 1900 to find even better varieties.

Entrepreneurs immediately began offering Turkestan alfalfa seed, often at premium prices. However, the Russian steppes are vast, spanning modern Kazakstan, Uzbekistan, Turkmenistan, Tajikistan and Kyrgyzstan. Importers found the cheapest seed, usually grown in irrigated fields near western ports, while Hansen searched for seed from the most hostile areas, near Lake Baikal in the east.

By 1916, the USDA was telling farmers the seed sold as Turkestan was inferior to American strains. However, since it wasn’t given authority to regulate seed until 1939, all the agronomists could do was tell farmers the ways to recognize poor offerings. The imported stock usually was contaminated with Russian knapweed seeds which were larger than alfalfa and ivory colored. Herbert Groh believes hoary cress hid in those shipments.

Despite looking a bit like a sedum, hoary cress denies our egocentric assumption that the parts of plants we see, flowers and tree canopies, are their raison d’ètre. This mustard lives for its roots. The whitish rhizomes spread under the surface, and whenever they need more nutrients, they send up new shoots, creating dense stands that are unified systems of deep probes seeking water and dense fibrous mats a few inches below ground. Any part that’s broken off by a spade or plow can send up a new stalk to regenerate itself.

The roots, leaves and stems contain sulfurous chemicals that inhibit germination of alfalfa seed, and even prevent growth by its own seedlings. The sticky, mucilaginous, brown seeds develop new colonies at a distance from their self-aggrandizing parents.

The most persistent local plants have been those growing along the sidewalk by the post office and across the road near a concrete foundation. Last year, the grey leaves took over the gravel spread between giant yuccas and a wisteria in the next yard to the north.

The sprouts that broke ground last week may have been killed by this week’s snow and cold, but the roots will survive: they’ve adapted to Finland. Other than herbicides that destroy everything, the only way to kill alfalfa weed is discing the roots some 20" down every few weeks for several years until the seed bank is exhausted. Hoary cress blooms each spring because subterranean lifeforms usually outlast our will to eradicate them.

Notes:
Groh, Herbert. “Turkestan Alfalfa as a Medium of Weed Introduction,” Scientific Agriculture 21: 36-43:1940, cited by Zouhar.

Kiemnec, Gary L and M. L. Mcinnis. “Hoary Cress (Cardaria draba) Root Extract Reduces Germination and Root Growth of Five Plant Species,” Weed Technology 16:231-234:2002.

Oakley, R. A. and H. I. Westover. Commercial Varieties of Alfalfa, USDA Farmer’s Bulletin 757, 1916.

Zouhar, Kris. “Cardaria spp.,” US Forest Service Fire Effects Information System on-line database,2004

Photograph: Hoary cress buds near the post office, 21 March 2009.