White Stopper

07 Jan

Eugenia axillaris

(Eugenia honors Prince Eugene of Savoy.  Axillaris no doubt refers to the axillary flowers and fruits. The axil is the place where leaf base meets stem.)

Myrtaceae, Eucalyptus Family

This week’s back-to-school frenetic frenzy prevented John’s and my usual leisurely Friday fieldtrip, but no problem,  my native plants class launched a new semester yesterday, and one of the species we learned is a species of mystery.    Today’s attempt may have more questions than answers.


Today’s photos by John Bradford, some taken in Kiplinger Preserve.

White Stopper is one of several stoppers native to Florida, representing one of the world’s largest plant genera, Eugenia, if  interpreted broadly.

White Stopper is a fine fixture in hammocks and native plant gardens around here, and is lovely with deep green leaves having purple petioles,  and potentially massive displays of white frilly flowers followed by red-then-black birdfood fruits.


Stop and look at those fruits a moment, they vary weirdly.   Most are smooth and “normal,” reasonable looking glossy berries.   CLICK for normal.   Some are lumpy, warty, and mis-shaped.   Compare the ones below with the “normal” photo.


Raisins?   Or under the influence of gall-makers?

That could be a matter of age or of growth conditions, but the deviations can be extreme.   Some of the fruits are  off-the-charts, grotesque, and sometimes hard and dry.


See what I mean?  The fruits can be seriously deviant.

Although I’m not sure where age and conditions end and gall-inducing pests start, Eugenias and relatives in general suffer from insect-induced fruit galls.   Anyone who habitually eats the related Surinam-Cherry may spit tiny larvae from between the teeth.

The abnormal WS fruits bothered Miami botanist Walter Buswell back in 1946, who said of today’s stopper: “often with few or many woody galls in place of the fruit.”  It will be interesting to slice open the berries from now on, especially the weird ones, and see if they are merely raisins, or if somebody’s home within.  There’s a poorly told story hiding here.

Another White-Stopper oddity is their fragrance.  Crush the leaves, and the smell isn’t powerful, despite membership in the Eucalyptus Family.  Stand next to one, and your sniff may disappoint.   But stroll on a hot day through a hammock where the species hangs out, and you may whiff a vague “skunky,” or “earthy” aroma, not unpleasant.  Reminds me of the fox cage at the zoo combined with freshly tilled soil.


Purple petioles

Why would a plant smell sort of musky, or earthy?  The perfume industry is grateful for plant musks.   Much easier to obtain than civets, and we want cruelty-free cosmetics!  What’s  musk anyhow?   There’s no single definition, sort of like pornography, it is vaguely defined but you know it when you smell it.   So alluring.   Put it in the perfume and stand back!  To over-simplify in the interest of you continuing to read,  plant musks are blends of volatile (easily evaporated) large organic molecules.  OK that is enough chemistry.

Cuban chemist Jorge Pino and collaborators in 2003 identified 42, count ‘em, named volatile molecules released from the leaves of Eugenia axillaris.   Repeat, 42.   Holy stinkpot!  And even more adrift after release when they meet the sun, air, and each other. Among the 42 are compounds used as fixative in perfume, as fragrance in marijuana, as medicines,  as giving beer its hoppy essence.  Some are described as smelling “musty” and “earthy.”  That smelly arsenal exists to counter infections, infestations, and miscellaneous pestilence.

The reason some people smell the shrubs and others fail is probably in part a matter of when the foliage unleashes its  chemical warfare.   True enough when warm, but there may be more to it than heat.   In this connection, the leaves have tiny translucent dots underneath, reasonably guessed to be hotspots where the P.U. sequesters.


Posted by on January 7, 2017 in Uncategorized, White Stopper


11 responses to “White Stopper

  1. Suellen Granberry-Hager

    January 7, 2017 at 1:28 am

    Just learned a whole lot about White Stopper that I missed in the Native Plants class! The flowers are absolutely gorgeous. I will be on the lookout for them.

    • George Rogers

      January 7, 2017 at 10:40 am

      Well Suellen, come visit Native Plants class ro cover those gaps! Hope 2017 is so far so good for you.

  2. theshrubqueen

    January 7, 2017 at 11:41 am

    Thank you, George, I am still working on sorting out the Stoppers! This is a great information for ID.

    • George Rogers

      January 7, 2017 at 9:55 pm

      Easy to do locally for the wild and commonly cultivated:
      White-pointy tips (W is a pointy letter)
      Spanish-round tips leaves smooth on top (S is a rounded letter)
      Simpson-round tips and with little tiny bumps all over the tops of the leaves, snazzy bark

      • theshrubqueen

        January 8, 2017 at 8:01 am

        Yay, that is great, thanks.

  3. Laure Hristov

    January 7, 2017 at 11:35 pm

    One of my least favorite plant dmells😩

    • George Rogers

      January 11, 2017 at 9:28 pm

      Well, I know how aesthetically pleasing your garden is…far more refined than low down polecat odor

  4. Annie Hite

    January 8, 2017 at 11:49 am

    Do you think the plant releases various odors in response to insect attacks or diseases? It seems to have quite an arsenal.

    • George Rogers

      January 11, 2017 at 9:28 pm

      That infection and attack can cause defense responses is well established, with a ton to learn for future plant physiologists and genetecists. Some of the stopper release may be attack response, and some may be promoted by certain growth conditions. Would be fun to experiment.

  5. Kristen Dell'Osa

    January 11, 2017 at 9:12 pm

    How many volatile molecules do plants usually have? Also, why would they have so many of them but we are unable to smell a strong smell all the time? Are you saying they are capable of controlling when the volatile molecules are released? That would be interesting to figure out what triggered the Stoppers to do so.

    • George Rogers

      January 11, 2017 at 9:26 pm

      Hi Kristen, Throughout the plant world, a huge number of volatile molecules. Any given plant, hard to say, but my guess is that white stopper is an extreme case. Some molecules are in low concentrations so we don’t smell them, and some probably don’t register much on your sense of smell. Thet fungal, bacterial, and buggy attack can trigger production of defense chemicals is clear, although an area where much more will be known in another decade. A term for this ball of wax is Systemic Acquired Resistance.


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