Excerpts from Jim Conrad's
Naturalist Newsletter

London Rocket, SISYMBRIUM IRIO

from the March  9, 2014 Newsletter issued from the Frio Canyon Nature Education Center in the valley of the Dry Frio River in northern Uvalde County, southwestern Texas, on the southern border of the Edwards Plateau, USA
LONDON ROCKET

In Uvalde maybe the most common rank weed of the kind you see up against the bases of warehouses, in abandoned lots and along neglected sidewalks, is the knee-high one shown above gracing the very edge of a side street.

A closer look at the flowering and fruiting branches, with tiny, yellow blossoms at the branch tip, and long, very slender fruiting capsules, with the capsules spreading away from the stem as they mature (important field mark) is shown below:

London Rocket, SISYMBRIUM IRIO, inflorescence

A closer look at individual flowers showing slender ovaries -- the future fruits -- erupting from the modest blossoms is seen below:

London Rocket, SISYMBRIUM IRIO, flowers with emerging immature capsules

The plant's large basal leaves are deeply lobed, as shown below:

London Rocket, SISYMBRIUM IRIO, leaves

This is the London Rocket, also known as Rocket Mustard, SISYMBRIUM IRIO, a member of the Mustard Family, the Brassicaceae. It's an invasive from Eurasia and Africa now found in disturbed sites in many countries. In the US it occurs mostly in southwestern states, though it turns up spottily throughout the country. I read that the name London Rocket comes from its abundance after the Great Fire of London in 1666. The English name "rocket" derives from the Middle French roquette, and the Italian rochetta, the latter diminutive of ruca, from the Latin eruca, applied to a kind of mustard plant. The name of the salad plant Arugula, also a member of the Mustard Family, goes back to the same roots.

London Rocket's flowers, young leaves, and seeds are all edible, but they are so spicy-hot and pungent that you can't eat much.