Firebush has Burning Needles

13 Jan

Hamelia patens

(Hamelia honors naturalist Henri L. DuHamel du Monceau.  Patens means spreading.)

Rubiaceae (Coffee Family)


Firebush.  Not taken today.  In fruit now.   Although memory fails me in some cases, all or most of today’s non-microscope photos are by John Bradford.

Today John’s and my Kiplinger  activity centered on photo equipment rather than exploration,  making this a good occasion for Firebush.  This colorful, drug-bearing shrub or small tree will ring bells with gardeners beyond those dedicated to native species.


As with most species that slip into mainstream gardening, Firebush over many years has wandered at the hand of humans around and far beyond its broad range from South America to Florida, divvied up into cultivars in far-flung nurseries, and redistributed willy nilly.  Its garden history is as willy as South Africa and as nilly as China.

My first encounter with Firebush was in the Caribbean, not Florida.    This sort of mixed up globe-trotting pattern is obviously standard for any given garden species.   I’m going to leave its cultivation to the innumerable websites concerned with growing stuff.  To summarize the fine points of cultivating Firebush: plant it, go away.


Or let the birds plant it for you, dispersing seeds from the pea-sized berries.    As is true of many species, the fruits mature through a red phase, then black, the two colors often clustered close together.   The plant world is rife with red and black juxtaposed as an attractant color combo for birds.    If you think about it and watch, you find red and black together in seeds, fruits, and flowers.


Let’s go a little more obscure into the secret life of Hamelia.  Firebush belongs to the Coffee Family, and like its kin, the shrub has paired leaves (or leaves whorled in 3’s) with a triangular flap called a stipule on the stem between the leaf bases.   Many plants have stipules, but that triangle between the leaf bases is a Coffee Family specialty.   When the twig is young, those triangular flap stipules clasp the baby stem tip before the leaves grow.


Stipule, triangular flap between two leaf bases.  The bud has grown and the stem is elongating behind the stipule.


This will help.  Picture the boy’s head as the stem bud.  The triangular sides to his hat are stipules.  CLICK

In many Coffees, the stipules hide a palisade of brown micro-teeth called colleters.    The colleter secretions presumably feed protective ants,  and/or protectively varnish the young bud tip under the stipular hat.


This is Wild-Coffee with a stipule removed to  reveal the brown glandular colleters.


Oddly though, in Firebush the colleters are either missing or too inconspicuous for me to find.  Instead, the Firebush stipules have a wet-looking glossy inner surface sealed tightly against tender stem tip.   As the tip elongates, the stipules remain on the side of the lengthening stem awhile, eventually to wither and drop.


Firebush stipule.No colleters apparent.  Instead the inner face (exposed) is wet-looking and sealed tightly around the bud by the two lips you see along the edges.    The (removed) bud was in that glossy groove.  A tight fit.

The protective mechanisms get weirder.  Many unrelated plants develop microscopic needle-shaped crystals called raphides inside their cells.    Did you every carry an armload of prunings to the compost heap, only to suffer a burning sensation on your exposed forearm?   Might be those little needles doing their job.   For decades, I (and many others) assumed the raphides to work merely by pricking the flesh, and then maybe melting into irritating acid.    But no…wrong…here is yet another example of the newly emerging complexities of the green world.

Biologist Kataro Konno and collaborators in 2014  documented the ability of raphide crystals to inject protein-destroying enzymes when they penetrate.  They give the victim a toxic shot, or a thousand of them!  More  precisely, the tiny pricks punch holes in cell membranes, allowing the toxic enzyme associated with the raphides to enter the victim’s cells.    Punji sticks.


Raphides from Firebush.  They look lke pickup sticks.

Flip over a leaf and look at the corners where the side veins join the main vein.    With a magnifying glass you can spot kinky white hair tufts.   Those nests, called domatia, presumably house predatory mites on  duty defending the foliage from leaf-bothering mites.


Firebush domatium, guardhouse for predatory mites

And speaking of mites, Firebush is a key player in research concerned with flower mites catching an inter-blossom lift from pollinating hummingbirds.  (Firebush benefits from many pollinators, including butterflies, especially where hummingbirds are scarce.    In its truly  tropical range Firebush seemingly depends mostly on hummingbirds for “the birds and the bees.”)   Flower mites are parasites able to steal pollen and nectar from the blossoms they invade.    Bad news for Firebush!    In some studies, those microscopic arachno-rascals have reduced the pollen and nectar substantially.     They come, they raid, and then fortified on pilfered booty they reproduce, only then to hop into a hummingbird’s nostrils airborne to the next bush.

the end

Extra notes for inquiring minds…

For  taxonomy within the species,  written by  botanist, Dr. Thomas Elias,  who revised Hamelia back in the 70s and then revisted Hamelia patens as a cultivated complex far more recently.   CLICK

Persons interested in more depth on the hitch-hiking mites, CLICK

Penetrating article on the raphide needle effect:   CLICKITY CLICK


Posted by on January 13, 2017 in Firebush, Uncategorized


5 responses to “Firebush has Burning Needles

  1. Laure Hristov

    January 14, 2017 at 9:26 am

    Thanks for more insight into this complicated plant! Never know for sure which cultivar you are buying Etc. and now I know why I get that burning sensation on my arms sometimes while working in the garden🤔Mystery solved! Your blog and the photography is always so interesting.

  2. theshrubqueen

    January 14, 2017 at 9:30 am

    Enlightening as always, thank you. Last week’s flower arrangement had Firebush in it and I was wondering why my thumb was worse for wear. Reinstating my mother’s cardinal rule of gardening – wear gloves!

    • George Rogers

      January 14, 2017 at 12:09 pm

      For sure…some nights after a day of handling diverse plants my forearms break out painfully, often during dinner…with no 100% clear explanation other then a lot of dermal contact with a lot of plants

      • theshrubqueen

        January 14, 2017 at 1:58 pm

        Undefined contact dermatitis! The odd thing to me was I couldn’t see anything so I poured some hydrogen peroxide over to clean anything and nearly the entire surface of my thumbprint bubbled tiny white bubbles!?

  3. George Rogers

    January 14, 2017 at 3:34 pm

    Right—you handle about a many odd plants as I do…don’t even know where you find some of them


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