We're lucky to have this is a strange plant with its fragrant, rough leaves and its oddball flowers in St. Louis.  And speaking of oddball, if you don't know the plant you might want to let Uncle Steve introduce it to you in this pleasant and short (1:51) VIDEO.  Unfortunately  he doesn't quite know what it is either, but there's something engaging about his demeanor.  Even that weird bent paperclip adds to the authenticity of it all. 

 

Many people might be tricked into thinking that this plant is from the Apiaceae (Carrot Family) because it seems to have umbels of flowers.  But technically those aren't umbels and those aren't even simple flowers.  Parthenium is in the Asteraceae, the Sunflower Family.  So each tiny "cauliflower" (to use Uncle Steve's lingo) is actually a flowerhead or composite flower or capitulum or pseudanthium (no shortage of terms to use!) filled with many tiny florets. 

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The tiny white fuzzy-looking flowerhead looks like no other St. Louis flower.  In the center of the flowerhead is a button of male disk florets - up to 35 of them.  But instead of being encircled by a perimeter of many ray florets, there are only 5 of them - all female.  These female florets don't have the long straplike ligules that we're used to seeing.  Instead they look more like tiny white ears.  (Apparently the ears haven't been washed very well because inside we can see the dark speck of its 2-branched style.)  Those 5 ears are quite famous.  In fact the whole genus is named after those lone female florets.  ("Parthenium" comes from the Greek word for "virgin".)

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To add one more curiosity, the scent of a Wild Quinine flower is described as being "pleasantly medicinal".  Now what could that mean?  By the way, the plant actually was used medicinally during WWI as a source of quinine to treat malaria. (The more famous source of quinine is the bark of the Cinchona tree, which is in the Coffee Family.)

 

But not everyone in the Parthenium genus is such a hero.  Parthenium hysterophorus (a.k.a. "Famine Weed") has become one of the worst invasives in India, Australia and parts of Africa.  It causes milk disease in livestock and respiratory problems in humans.  Glyphosate is not effective in controlling it.

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For those of us trying to better learn our different flower types, Parthenium integrifolium can help:

 

STANDARDIZED FLOWER COMPARISON FORM: (please click for GLOSSARY)

INFLORESCENCE: A single, large "pseudanthium" (false flower) from the Asteraceae can by itself be considered an inflorescence.  It's a very refined, condensed inflorescence in which the architecture has shrunk to lilliputian tininess.  But it's still there for the littlest creatures to enjoy.  As mentioned earlier, this flowerhead is composed of a center button of 15-35 male disk florets, with 5 female florets evenly spaced around the perimeter like little ears.

The pseudanthiums themselves can be arranged into an "inflorescence of inflorescences" (a "compound inflorescence" or "synflorescence").  They form dense flat-topped clusters (corymbs) with each cluster on its own stalk.

INVOLUCRE: The involucre that holds the whole flowerhead together from below is covered with 2 rows of phyllaries (floral bracts).  There are 5 phyllaries in each row.  The 5 phyllaries in the inner row are broader in shape.  The 5 phyllaries in the outer row are oblong in shape and have appressed hairs.

CALYX: The sepals of the 5 female florets have been modified into several short awns.

COROLLA:  Each tiny disk floret has a white 5-lobed corolla.

ANDROECIUM: The male disk florets have 5 stamens with distinct filaments but with dark anthers held tightly together.

GYNOECIUM: Each of the 5 female ray florets has an inferior-positioned ovary composed of 2 united carpels with a bifurcated style and dark stigmas.

FRUIT:  The ovaries mature into brown, rounded clusters of cypselae (achene-like fruits).

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For more information on the Wild Quinine please click on MissouriPlants.com to view their information-rich photos (including a great close-up of a single flowerhead).  To read a fine description, please click on IllinoisWildflowers.info.

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- Michael Laschober