Saturday, April 30, 2011

A Tale of Two Strawberries

 As promised: a brief history of the cultivated strawberry.

Meet Amédée-François Frézier, 18th century spy, mathematician, cartographer, strawberry smuggler, and general international man of mystery.

Amédée-François Frézier.  Handsome, no?
Frézier's most lasting work would be a royally-commissioned reconnaissance mission for Louis XIV in South America between 1712 and 1714.  After carefully characterizing coastlines, flora, fauna, and, most importantly, Spanish assets, Frézier hopped back onto his merchant ship to Marseilles with all kinds of loot, including five specimens of a new species of strawberry whose fruits he described for posterity as being "as large as a whole Walnut, and sometimes as a Hen's Egg."  This was good news for Old World strawberry cultivation since the few species currently available to Europeans bore delicious but rather lilliputian fruits.

Frézier's illustration of Chilean strawberry, enormous fruit and all.
It could very well have been familial pride that drew Frézier to the familiar trifoliate-leaved plant with the unusually large berries that he encountered during his time in Peru.  Frézier is a bastardization of fraise, French for strawberry, and was purportedly derived from a knighthood bestowed upon Frézier's tenth century ancestor Julius de Berry (I'm not making this up, I promise) by King Charles the Simple in return for serving up an excellent crop of them for a feast at a time of year (early May) that seemed somewhat miraculous.

But alas!  Frézier was in for an unwelcome surprise upon his return home.  The strawberry plants that had once borne such incredibly large fruits in Peru bore absolutely none on French soil.  The plants propagated themselves perfectly well by sending out vine-like runners with small satellite plants that were sent all over Europe for horticulturalists to coddle and fuss over.  But the fact remained that for 50 years no one could consistently entice Chilean strawberries to, well, make strawberries.  When they did produce fruit, no one seemed to know why.

The problem?  In choosing plants with the largest fruits from Peru, Frézier had inadvertently selected all females.  The Chilean strawberry, it turns out, is one of the rare species in the plant kingdom to have separate sexes, a state known to botanists as dioecy (Greek: di- two, oikia- house).  Most plants are hermaphroditic- the flowers on an individual plant possess both male and female sexual apparatus, and most of these are capable of self-pollinating.  Perhaps these odds were the reasoning behind Frézier's oversight- he just assumed that the plants he took back with them were able to self-pollinate in order to produce fruit.  (See this wiki for a brief primer on the dizzying world of plant sexuality: "It's complicated" doesn't quite begin to cover it.)

The plants that Frézier had overlooked in Peru- those that infrequently bore small, irregular fruits, or worse yet, none at all- were not evolutionary duds, they were simply the males of the species whose chief reproductive duty is to produce pollen, not to bear fruit.  The solution was suggested by leading strawberry expert Antoine Nicholas Duchesne in 1766: to find a suitable pollen donor among strawberry species available in Europe so that the female flowers could be pollinated and thus bear fruit.  This solution was accidentally implemented by gardeners who planted other species of strawberry amongst the Chilean strawberry, allowing bees to cross-pollinate all the species.  The winning candidate for consistently pollinating the Chilean strawberry was the Virginian strawberry, brought to Europe from the meadows of what are now the eastern United States some 100 years before the Chilean strawberry's landing.

Eventually, these mid-18th century crosses of North and South American strawberries in European gardens yielded the grand prize: modern cultivated strawberry, or Fragaria x ananassa (the "x" denotes the hybrid nature of the species), available in markets across the globe.  Voilà!  French spies, mistaken identities, and an ultimate, highly profitable and delicious redemption.

Fragaria x ananassa: modern cultivated strawberry

*Fun fact*: the success in the pairing of the Chilean and Virginian strawberries may in part be attributed to both species being octoploid.  That means that instead of having two copies of each of their chromosomes like we do (a state called diploidy), these strawberry species have eight.  This also makes them good for home DNA extraction since they have a lot of DNA.

I should also note that G.M. Darrow's book The Strawberry: History, Breeding and Physiology, was an indispensable resource for this post- it is available in full through the USDA website, here.


  1. It's also an epic transcontinental love story: Chilean and Virginian strawberries find true love in Europe!

  2. You would have thought the French would have taken l'amour into consideration!

  3. Julius de Berry- some stories just beg to be told. Who knew strawberries were so interesting? Or that french gardeners would wait 50 years for good fruit?