28 Jan


Lepidium virginicum

Brassicaceae (Cruciferae)

[Three additional species of Lepidium live in Florida, none of them native: two in the Panhandle and “Lesser Swinecress” in our area, not resembling today’s species.]

Lepidium at Kiplinger

Yesterday John and George dodged a deluge to enjoy raindrops on the flowers in the Kiplinger Natural Area in Stuart, home of spectacular Loblolly Bays, non flowering in January yet attractive with red winter leaf coloration.

Dominating the disturbed trailside was Pepper-Grass (Lepidium virginicum), which is neither a grass nor related to red or black pepper.  A better name for this coarse native weed might be “Stink Mustard.”  This member of the Mustard Family reeks when crushed a little like its cousin Horseradish.  The Mustard Family is perhaps better known by the older name “Cruciferae,” as in “eat your cruciferous vegetables,”  for instance, cabbage, brussel sprouts, and cauliflower, which are all different cultivars of the same species.  They are called “crucifers,” not because eating them resembles being crucified to kids brought up on pop tarts and Wendys, but rather because the four petals form a cross.  The novel fruits are flat with two covers that fall away to leave a translucent membrane.   Vocabulary lesson:  the fruits are called silicles (SILL–ah-culls, oval) or siliques (a sill-EEK is long and SLEEK).

Flowers and silicles (photo by JB)

Different plants poison their pests differently, and Crucifers are regular Nozzle Nolens.  Crush Pepper-Grass, and the sharp mustard vapors penetrate your sinuses like a knife.   The kick comes from sulfur-based “mustard oils” more properly known as glucosinolates.  Until activated, the glucosinolates (glue-coe-SIN-oh-lates) are benign.  They and the activation-enzyme myrosinase reside in separate parts of the plant cells until a lubber grasshopper takes a munch.  Then, like two tubes of epoxy, the glucosinolates and enzyme mingle for hot stinky action in the crushed tissues.  We could linger the chemistry, but that would get boring to the non-chemists (like us), and we’d get in over our heads fast.

Low-dose glucosinolates can be tasty like mustard on a wiener, or cole slaw, or sushi with wasabi.  And the good news is that glucosinolates may inhibit cancer development, although the jury is still out.

Glucosinolates are wasted on these Great White Southern caterpillars (photo by Edith Smith)

Anti-herbivore toxins deter most vegetarians, but life is one big evolutionary race between the eaters and their victims’ defenses.  Coyotes do catch roadrunners, and creatures do eat Lepidium.  Varied cooties, ranging from aphids to butterflies, have developed enzymes to deactivate the mustard oils, allowing access to those colon-cleansing cole vegetables.  Pepper-Grass supports native and non-native mustard-proof butterflies.   Examples include the Cabbage Butterflies (duh) as well as the Checkered White Butterfly, Great Southern White Butterfly, and the Falcate Orange Tip Butterfly (in northernmost Florida).

In conclusion, eat your vegetables.

(The photo of the Great Southern White Butterfly on the Lepidium is courtesy of Edith Smith at Shady Oak Butterfly Farm.  Visit her remarkable web site CLICK)

1 Comment

Posted by on January 28, 2012 in Pepper-Grass


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One response to “Pepper-Grass

  1. Steve

    January 29, 2012 at 6:57 am

    L. virginicum is a classic “winterweed” here in FL, and edible by people as well. Like many mustards it has a piquant flavor, similar to the unrelated Black pepper (Piper nigrum). It is not uncommon in lawns, and other disturbed places. Fruits of this species are atypical looking for a silique, which are often slender and elongate, however they do possess a gynophore (one of my favorite botanical words). My students like to ask me, “what’s a gynophore?”, after blushing, I explain to them that it is the elongate stalk bearing the pistil (at the base of the fruit). Photographs and illustrations of this organ may be found at:


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