Tips for Control of Yellow toadflax

Plant annual grasses or strong perennials to shade it out and compete. Fertilize the soil to provide choice competitors with the appropriate irrigation, humus, calcium, phosphorous, and aerobic bacterial populations cultivars require. Yellow toadflax flourishes in tougher situations such as road salt, ocean spray, neglect and drought without competition from less adaptable cultivars and even natives. It resists herbicides. Remove seeds and pull out and toss out as much of roots as possible since it can regenerate from parts that remain behind. Starve roots by repeatedly cutting stems. It dislikes acidic soil, sogginess, or heavy shade, so use these to combat it.

Bio-Controls for Yellow toadflax

In the wild, certain imported insects have provided the most effective controls. You can mail-order the leaf-defoliating moth, Calophasia lunula, the most commonly recommended bio-control. Two weevils, Gymnaetron antirrhini and Gymnaetron netum, eat its seeds (I wonder which is the lesser of two weevils?) and a promising beetle, Brachypteolus pulcarius, feeds on its ovaries (how grim!). Scientists continue to test Eteobalea seratella and Eteobalea intermediella moths and Mecinus janthinus, a weevil, for effectiveness in controlling it. You must obtain permits from the USDA before transporting and releasing any of these insects. The risk: any bio-control may backfire and start its own infestation. This infestation could then require another imported predator to control the bio-control, which in turn could backfire, and so on.

Another foreign invader, Canada thistle, Cirsium arvense stowed away in hay to feed the horses of British General Burgoyne during his attack on the U.S. during the War of Independence. Burgoyne lost the war, but like the American colonialists, the well-concealed, adaptable, and hardy Canada thistle triumphed to make its own colonies and command its place on “Most Wanted: Dead not alive” lists. Since 1795 in Vermont and 1831 in NY, Americans wrote laws mandating its removal, yet it revolts against man-made laws. Even wildflower guides consider it a pernicious weed.

Canada thistle germinates and grows best as conditions fluctuate. This rebel thrives with neglect, drought and salt and falters in stable fertile soil, deep shade, sogginess, or peat bogs.

It has its uses. It provides a food as nutritious as alfalfa. In old Scotland, after they crushed its prickles in a mill, the Scots fed it to cattle and horses. It has provided both food and folkloric medicines for people.

Left: Canada thistle in simultaneous flower and seed… Right: attracts pollinators to help it spread