General Weed Science Principles

Michener (Reference Michener1872) offered eight general weed management suggestions. First, he wrote, never allow weeds to produce and sow seeds. For his second point, he used his medical experience as he paralleled infestations of some weeds to leprous spots and stated that tillage should be avoided to eliminate spreading vegetative fragments into areas of the field not infested. Third, Dr. Michener suggested to prioritize removing all perennial weed roots from infested fields, followed by frequent scouting to remove any new shoots. Fourth, he wrote that leaves are the primary source of plant “digestion, assimilation and respiration” and the most accessible and vulnerable part of the plant to remove. Fifth, he recommended eliminating leaves as soon as they form to starve weed roots. Michener suggested that a key to weed control is preventing leaf production. He included information from and quoted from a letter written by Caleb Bemet (1843) of Three-hills Farm in New York that was published in the October 15 Farmers’ Cabinet, and American Herd-book about Canada thistle [Cirsium arvense (L.) Scop.] control; Bernet stated that leaves are as essential to plants as lungs are to animals and that leaves and roots are mutually dependent. He stated that Canada thistle had been eradicated (and could be by other agriculturalists) by continuously removing all leaves and stalks during June, July, and September for one or two seasons. As a sixth recommendation, Michener (Reference Michener1872) suggested hand removal; hoeing in gardens; or plowing, cultivating, and harrowing fields as the best methods to prevent weed leaf formation. He also suggested that suffocation (i.e., mulch with straw or bagasse) or the addition of poisons (spent tan) may also be used. His sixth suggestion also included the recommendation of a practice of “high farming,” which was described as production practices that encourage luxuriant crop growth to “suffocate” weeds. The seventh of Michener’s recommendations was “other subordinate means” noted in his book. The eighth and final recommendation was a reminder that weed seed buried in the soil seedbank would be exposed by tillage and would germinate after the farmer thought weeds had been eradicated, so one should continue to scout for and remove new weeds that emerge.

Agricultural Boards of Health Proposed

In the final pages of general weed management concepts, Michener (Reference Michener1872) stated that noxious weeds infesting farmland was not just a local problem nor a problem limited to agricultural interests but a national problem. He wrote that many acres of highly productive farmland had become useless because some landowners failed to prioritize weed control. His philosophy was that noxious weeds were a national problem that would not be solved without laws enforced to mandate control. Again, drawing on his training and experience as a physician, he made the analogy that municipalities had the authority to impose quarantine laws against invasion of human or animal diseases, could rigidly enforce hygiene regulations, and could even forcibly remove occupants from their premises if the threat of highly infectious disease existed. He proposed that similar authority should exist to govern the “health” of plant agriculture in farm districts. Michener recommended that “Agricultural Boards of Health” be established in districts to inspect, oversee, and regulate clean crop seed and grain sales with additional responsibility to inspect farms for noxious weeds. These boards of health would have the authority and resources to temporarily remove landowners who failed to control problematic weeds on their property. He suggested that property management be assigned to agricultural health board “agents” to remove the noxious weeds from the neglected land. Agents would be compensated either by revenue generated from the sale of the cleaned crop or from a general fund managed by the board and were essential to protecting the district’s resources.

Weeds and Specific Management Suggestions

Weeds described in the pages following Dr. Michener’s (Reference Michener1872) general weed management suggestions were written in the Linnean arrangement of plants similar to that of Agricultural Botany (Darlington Reference Darlington1847), American Weeds and Useful Plants (Darlington and Thurber Reference Darlington and Thurber1859), and Gray’s (Reference Gray1842) Botanical Text-Book. Like these earlier texts, Michener (Reference Michener1872) provided scientific names, life cycles, botanical descriptions, habitats, common names, sources or origins of introduced plants when known, flower and/or fruiting periods, and general observations of the 100 weeds he viewed as most important for American agriculturalists. Michener’s text differs from Darlington and Thurber’s (Reference Darlington and Thurber1859) American Weeds as no images were provided to assist with weed identification. Two additional differences exist between Michener’s (Reference Michener1872) text and the earlier texts by Darlington (Reference Darlington1847) and Darlington and Thurber (Reference Darlington and Thurber1859). First, Michener’s (Reference Michener1872) text is focused solely on the plants he considered weeds, whereas Darlington (Reference Darlington1847) and Darlington and Thurber (Reference Darlington and Thurber1859) described both weeds and plants considered useful for other purposes. The second and perhaps more important difference is that despite limited control options in the late 19th century, Michener (Reference Michener1872) attempted to relate management suggestions to control most of the weeds described in The Weed Exterminator.

Weeds known or thought to be toxic to humans or livestock are documented in Michener’s (Reference Michener1872) as well as Darlington’s (Reference Darlington1847) and Darlington and Thurber’s (Reference Darlington and Thurber1859) texts. Michener (Reference Michener1872) indicated toxicity for weeds, such as common moonseed (Menispermum canadense L.), poison sumac [Toxicodendron vernix (L.) Kuntze, synonym of Rhus venenata DC.; WFO 2023h], Atlantic poison oak (Toxicodendron pubescens Mill., synonym of Rhus toxicodendron L.; USDA-NRCS 2023), spotted water hemlock (Cicuta maculata L.), poison hemlock (Conium maculatum L.), black nightshade (Solanum nigrum L.), climbing nightshade (Solanum dulcamara L.), Darnel ryegrass (Lolium temulentum L.), and common St. Johnswort (Hypericum perforatum L.), thought to cause scabs and cutaneous ulcers on white-skinned feet and the noses of cattle and horses. Michener (Reference Michener1872) stated that his experiences and observations of populations of common St. Johnswort in the years following 1842 differed from those Darlington (Reference Darlington1847) shared in Agricultural Botany. These two authors’ observations paralleled in the fact that although populations of common St. Johnswort had been abundant for many years, it did not emerge in 1842. Darlington speculated that it did not emerge anywhere in the entire state of Pennsylvania in 1842, with only sparce populations in 1843. However, common St. Johnswort was again abundant by the time his text was published in 1847. By comparison, Michener (Reference Michener1872: 8) reported that populations of common St. Johnswort were sparse as long as 3 decades after 1842, relating that housewives had not found sufficient quantities to “keep up a supply of ‘Red Oil’ to treat corns and burned fingers.”

Michener (Reference Michener1872) did not provide specific management suggestions for every weed he described in his book. For several species of weeds, Michener recommended careful monitoring for volunteers or escaped plants of plants intentionally cultivated, such as common evening primrose (Oenothera biennis L.), Mexican pricklypoppy (Argemone mexicana L.), and several others. He recommended hoeing, hand removal, scythe, cultivation, and so on to prevent seed production from weeds like lambsquarters (Chenopodium album L.), slim amaranth (Amaranthus hybridus L.), velvetleaf (Abutilon theophrasti Medik.), and Fuller’s teasel (Dipsacus fullonum L.). Hand removal was specifically recommended for blindeyes (Papaver dubium L.), little hogweed (Portulaca oleracea L.), devil’s beggarticks (Bidens frondosa L.), common mullein (Verbascum thapsus L.), and moth mullein (Verbascum blattaria L.) to prevent seed production and seed rain from these plants. Michener mentioned several farm and garden implements useful for management in his recommendations for various weeds, including the grubbing hoe, fork-spade, horse-hoe, cultivator, plow, harrow, “dock-spit,” and mower. Michener provided neither a description of nor use instructions for the “dock-spit” in his textbook. The authors believe this to be a smaller variation of an implement John Worlidge (Reference Worlidge1687) credited Gabriel Platt for inventing to uproot shrubs and similar weedy vegetation which he described and illustrated in Systema Agriculturæ (Figure 1). A variation of this tool specifically associated with uprooting dock was later described by Pitt (Reference Pitt1806), but he called it a docking iron (Figure 2). Loudon (Reference Loudon1871) also briefly described the device in An Encyclopedia of Agriculture (Figure 3).

Figure 1. Illustration showing the use of an implement to uproot shrubs from Systema Agriculturæ (Worlridge Reference Worlidge1687).

Figure 2. Description of the docking iron from “On the Subject of Weeding” (Pitt Reference Pitt1806: 256).

Figure 3. Description of a tool to uproot dock from “Of the Implements of Manual Labour Used in Agriculture” (Loudon Reference Loudon1871: 371).

Michener (Reference Michener1872) also stated that it was good practice to have a “brush-heap” on which weed biomass could be piled to periodically burn, that is, to practice field sanitation. But he related his own failed experience burning Scotch cottonthistle (Onopordum acanthium L.) biomass (“I thought I had burned every seed it produced”; Michener Reference Michener1872: 59): one or more volunteer plants emerged every year for 12 yr. His experience with Scotch cottonthistle also helped him realize the potential negative effect of introducing plants of “doubtful character” to the farm, garden, or landscape. Michener’s failure to eradicate Scotch cottonthistle was not the only reason he was convinced that burning would not eliminate all perennial weeds. He also related John Bartram’s observation with butter and eggs (Linaria vulgaris Mill.) in his text. Although Michener did not state the source, he quoted portions of a letter dated June 16, 1758, in which John Bartram wrote Philip Miller a list of the most troublesome plants of Pennsylvania pastures and fields (Darlington Reference Darlington1849). In that letter, Bartram stated that butter and eggs, “the most hurtful plant” in northern pastures, could not be eradicated from pastures by “spade, plough nor hoe” nor by “burning log piles that burned the earth” 0.15 m (“half a foot deep”) (66), after which populations reemerged densely enough to prevent grass growth. However, Michener (Reference Michener1872) then went on to relate his success eradicating butter and eggs by smothering a population 10 m² (“2 rods square”) with piles of weed stubble 1.5 m (“5 feet”) deep over the infested area, to which he added 50 bushels magnesium lime, then let cattle trample the area in autumn of the next year. He also related that a small infestation of butter and eggs had been eradicated from his garden after only 5 yr of attentive cultivation, which entailed removal of every piece of the plant and thread of root as short as 2.5 cm (1 in.).

Another recommendation Michener (Reference Michener1872) suggested as a management practice for weeds such as sheperd’s purse [Capsella bursa-pastoris (L.) Medik.], common dandelion (Taraxacum officinale F.H. Wigg.), and wild garlic (Allium vineale L.) was use of production practices he termed “high farming.” High farming was explained as part of his management suggestions for wild garlic, which included the addition of lime, plaster, and “the farrago of modern fertilizers” (100) to agricultural lands to crowd out or smother noxious weeds, a relatively new agricultural practice. Webster’s New Dictionary of the English Language defines farrago as a “confused collection.” Tilden (Reference Tilden1867) explained “high farming” as maximizing production inputs to maximize productivity of small farms, rather than increasing farm size with lower production inputs, using farm practices in the Netherlands as the example. Michener (Reference Michener1872) also stated in the management recommendation for wild garlic as well as for star of Bethlehem (Ornithogalum umbellatum L.), another bulbous weed, that in addition to high farming, fields overrun with these two weeds had been cleaned by planting oats two consecutive seasons.

Observations and management suggestions for annual ragweed (Ambrosia artemisiifolia L.), which Michener (Reference Michener1872) described as “The Weed” most abundant in American farmland, were that tillage appeared to encourage emergence of annual ragweed, whereas competitive grass crops, such as grains, reduced the populations by smothering. He was uncertain if the soil seedbank contained abundant quantities of seed for population emergence or if annual seed production resulted in these dense populations. He related the weed management strategy shared with him by a deceased housekeeper, whom he held in high regard, who related that she prevented the production of seed by any weed in her garden 7 yr and as a result had minimal weed pressure. He speculated that this method could work to reduce annual ragweed presence.

Another strategy Michener (Reference Michener1872) used to encourage agriculturalists to control weeds was psychological. In fact, by today’s standards, some may call it bullying. He used terms or phrases, such as “sluggard occupant,” “negligent,” “a reproach,” “indolent,” “slovenly,” “would-be farmer,” “poorer cultivator,” “lazy man,” to imply that the presence of certain weeds was an indication of poor management. Webster’s New Dictionary of the English Language defines slovenly as untidy or lazily or carelessly done. This is likely the rationale for Michener’s (Reference Michener1872) suggestion that farms be inspected for noxious weeds and crop management confiscated by agents of the agricultural boards of health until noxious weeds were removed. His attitude toward spiny cocklebur (Xanthium spinosum L.), which he encountered at Port Deposit, Maryland, on the Susquehanna River, was that every citizen should defend the country’s best interest against such pests. Furthermore, he stated, “it behooves every good citizen, to extirpate it, wherever it may appear” (42). He went on to share his disbelief that spiny cocklebur had become such a nuisance in the streets of an unnamed city that an ordinance was enacted by city officials in which the plant was denounced as Canada thistle (Michener Reference Michener1872).

Michener (Reference Michener1872) wrote almost two pages regarding management of oxyeye daisy (Leucanthemum vulgare Lam.), which he indicated was widely dispersed. He stated that hand removal, digging, plowing, and mowing were effective methods of control. However, he warned that this weed matured seed while still in bloom and therefore must be removed and deposited onto a burn pile before flowering. He also related the experience of his neighbor, who, with two small boys, removed every oxeye daisy from the field, roadside, and every place that could not be plowed and subdued the problem in “a very few years (8 or 10)” (49).

In a lengthy explanation of the mischievous formation of rhizomes by Canada thistle, Michener (Reference Michener1872) labeled the weed one of the most vile of American agriculture. He advised agriculturalists never to allow any thistle to produce seed and to plow, harrow, or fork-spade to thoroughly pulverize soil every few days throughout the season and the next if needed and to hand pick all to remove all roots exposed on the soil surface. Michener even went on to recommend a herbicide treatment of a small handful of a mixture of 3 parts salt (NaCl) to 1 part “copperas” (FeSO₄) to Canada thistle “parent” stalks after cutting the stalk below the soil surface with a chisel-shaped tool. He hoped this mixture would be translocated to shoots sprouting from the rhizome, “the juices of the parent carrying the poison to its attached and still dependent offspring” (57).

Michener (Reference Michener1872) quoted almost an entire page on the observations Curtis (Reference Curtis1777–1798) shared in Flora Londinensis about the invasiveness and crop competition of field bindweed (Convolvulus arvensis L.). He described field bindweed as having “indomitable vitality,” then stated that the only method of bindweed eradication was “suffocation”—either smothering the weed with weeds or rubbish or “incessantly stirring” soil, taking care not to spread the rhizomes further in the process.