Invading garlic

Allirai petiolata (garlic mustard)

Garlic mustard is native to Europe, western and central Asia, and nothern Africa. As a biennial, in the first year of growth, plants form clumps of round shaped, slightly wrinkled leaves, that when crushed smell like garlic (hence the name...). The next year plants flower in spring, producing white flowers that release seeds in mid-summer.

Garlic mustard leaves are a great addition to wild salads, providing a mild flavour of both garlic and mustard. Garlic mustard was once used medicinally as a disinfectant or diuretic, and was sometimes used to heal wounds.

In the late 19th century garlic mustard was introduced in North America as a culinary herb, and since has gone on to become a very problematic invasive species. The success of garlic mustard, like that of other invasive species, is due to its lack of native competitors. Garlic mustard produces a variety of compounds that reduces its palatability to herbivores. Interestingly, in its native habitats, some herbivores have co-evolved to feed happily on the plants. But these insects and fungi that feed on it in its native habitats are not present in North America, and this leads to more garlic mustard seeds, allowing it to out-compete native plants. Even white-tailed deer, the scourage of many Eastern woodlands, don't eat the garlic mustard, preferring neighboring plants, which frees even more space for the garlic mustard to spread.

Revenge in a name - Sigesbeckia orientalis

Sigesbeckia orientalis

Carl Linnaeus is often called the Father of Taxonomy. While the crtieria he used for taxonomy have largely been replaced, the hierarchical classification and custom of binomial nomenclature that he established remains. 


While many criteria went into determining the binomial name of a plant, at least in one case, revenge was the main criteria. When Linnaeus announces his discovery that plants produce contain male and female organs and reproduce sexually, some of his contempories responded with shock and contempt. One of them Johann Siegesbeck called his idea "loathsome harlotry" and wondered "who would have thought that bluebells, lillies and onions could be up to such immorality?"  Linnaeus got even by naming St. Paul's wort, an ugly, foul-smelling weed that grows in the mud, Sigesbeckia orientalis.

Who's afraid of "superweeds"?

A recent post in The Atlantic decries that appearance of RoundUp-resistant weeds popping up in fields of GM crops, and uses this a call for the abandonment of GM technology.

Amaranthus hybridus

The only problem in his thinking is that "superweeds" started popping up way before the advent of GM technology and the deployment of RoundUp-resistant crops. For example, atrazine was one of the most widely used herbicides in eradicating plant growth on road shoulders, and is still widely used in agriculture. Weeds resistant to atrazine started to be noticed in the 1970s. My Ph.D. adviser Joseph Hirschberg isolated the first gene for herbicide resistance in 1983 from an atrazine-resistant Amarnthus hybridus that had been isolated from the side of a highway. This was way before any GM crops had been developed.

So as long as herbicides will be used in modern agriculture, there will always be the problem of spontaneous resistance, just as as long as we use antibiotics, antibiotic-resistant bacteria will also crop up.  GM technology is not the cause of the resistance. The challenge is in designing the best use of herbicides to ensure the best agricultural yields for the farmers, while protecting our environment as best as possible.But that's the subject of another blog.