Roquette Science

Cakile lanceolata

Brassicaceae (Cruciferae)

Today the lively Lakelas Mint Chapter of the Native Plant Society, John, and I walked the narrow dune-hammock between the sea and the highway on Hutchinson Island.  Such botanical bounty!:  Baybeans and Railroad Vines in blossom, Christmas Berry in berry and bloom,  Stoppers, Blolly, and by golly plenty more.  An odd little standout is Sea Rocket…and of course question number 1 is why “Rocket”?

On this Merriam-Webster’s Collegiate Dictionary sez: From Middle French, “Roquette,”  for arugula  or “any of several plants of the Mustard family.”

Another name for the Mustard Family is the Cruciferae (crew-SIF-eh-ree),  as in “eat your cruciferous vegetables,” the crux of the matter being the four petals forming a cross (crucifix).   There are, incidentally, 6 stamens—four long and two short.  So you can always tell any old Crucifer, from Cabbage to a Wallflower by the same basic flower construction.  They all look alike.

(Or at least they all used to.  DNA study is gerrymandering the family boundaries.)

Sea Rocket (by JB)

The Mustard Family is a pungent bunch.  You may notice there’s low P.U. until you mash the leaf.  Then “mustard gas” rises assertively.  They work like one of those light sticks for rock concerts and flat tires, with two key components stored separately and no reaction until smashing the inner glass  capsule mixes the stuff and lets there be light, or in our case lets there be wassabe.

The succulent beanlike fruits separate into two segments, one segment remaining anchored on the mother plant, the other segment breaking free carrying one or few seed(s) in a protective corky padded space-capsule to blow and drift in wind, sand, and waves to a new start.  Thus they get around, and Cakile species extend up and down seashore and freshwater-inland coasts from Santa to St. Tropez.

Sea Rocket fruits. Look closely and note that these rockets have two stages. (Photo by Wayne Matchett)

What’s more subtle and mysterious is the short-distance migratory cycle.  Now please be patient with redundancy for emphasis:  the fruit breaks into two segments: one goes and sows wild oats, and the other stays home.  Sound like the beginning of a parable.  Maybe the parable helps answer the question of how this delicate-looking wildflower occupies stormy, salty, eroding, windswept beaches where so little grows.  We better take a closer look at their habitats. There are actually two habitats, generally speaking:  the actual beach and the beachside dunes.

Remarkably the beach individuals reportedly grow more rapidly and make more seeds than their dune neighbors, and this matches my limited observations.  Reasons to prefer beachfront property seem likely to include natural fertilization by decaying seaweed on the beach, and more competition up on the dune.

Now let’s work in a fact of life well known to any coastal dweller or CNN viewer attuned to the ravages of the aptly named Sandy.  At stormy times the natural action of wind and waves is to relocate things that begin on the beach onto the dunes.  So how do Sea Rockets manage to hang on and repopulate the beach?  Here are three scenarios to keep Cakile on the beach:

1.  The Apron Strings Scenario.  Recall the fruit segment attached to Mama Rocket.  Most Cakile repopulation is within spitting distance of the mother plant.  Cling, be fruitful and multiply, building up a self-replenishing clump, until a hurricane rearranges the sand (and even then the rearranged sand will likely have Cakile segments in it).

2.  The YoYo Scenario.  An uphill-downhill cycle from harsh but fertile beach up to a safe but crowded dune,  and then back to the beach is nice to imagine. What goes up must come down.  Fruit segments and entire uprooted tumble-weeds with the clingers could erode back down to the beach cyclically.

3.  The Gilligan’s Island Scenario.  That upper fruit segment breaks free to roam.  They drift  ashore and establish new clumps.  By the way, who pollinates a lone castaway?  At least some Cakiles can self-pollinate.

To sum it all up, part of what makes Sea Rocket so extra-pretty is its indomitable will to look like a delicate wildflower in the face of sand-blasting and cyclones.

Better a rockette than a wallflower.