The plant of the day for Thermidor 27 (also known as August 14) is Rapeseed (Brassica napus). The common name is derived from the Old English word (rapum) for another member of the Brassica family, the turnip. Other plants in the Brassica family include mustard and broccoli.
Rapeseed oil has been used for centuries as lamp oil, and cooking oil. A particular cultivar, Canola, is used to make canola oil, the third leading vegetable oil in the world (after soybean and palm oil). Rapeseed oil is also used in the manufacture of biodiesel fuel. Rapeseed plants are primarily grown as fodder but the greens are edible and are similar to bok choy and kale.
I learned all of this from the great Wikipedia article which has much more information and great pictures:
Although the appearance of rapeseed in the French Republican Calendar which was created in 1793 indicates that this plant has been used by humans for a long time, there are several controversies swirling round rapeseed. Monsanto created a genetically modified version of rapeseed that is resistant to Round-up, a pesticide used to kill noxious weeds. This genetically modified version cross-pollinated with other rapeseed and Monsanto then successfully sued Canadian farmers whose rapeseed crops were found to contain their patented modified version.
The picture of a field of rapeseed comes from this website which offers classes on making biodiesel fuel:
The closeup of the flower comes from the Centre for Research in Environmental Science at the University of the West of England at: