Thimbleweed with its spiky seedhead is a not-to-be-missed work of art that takes stage throughout June in our St. Louis woods.  

 

Thimbleweed (Anemone virginiana) is a native perennial in the Ranunculaceae.  But there are other plants from other families that also have spiky centers.  Since it's so easy to get them confused and since some of them are real troublemakers, we've put them all together in a list below.  (Click on any of the names to view useful photos from MissouriPlants.com.)

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• Anemone virginiana (Tall Thimbleweed - from the Ranunculaceae) native

• Carduus nutans (Musk Thistle - from the Asteraceae) - a Missouri Noxious Weed 

• Cirsium altissimum (Tall Thistle - from the Asteraceae) native

• Cirsium discolor (Field Thistle - from the Asteraceae) native

• Cirsium vulgare (Bull Thistle - from the Asteraceae) noxious weed in 9 states, but the National Flower of Scotland!

• Dipsacus fullonum (Fuller's Teasel - from the Caprifoliaceae) - a Missouri Noxious Weed 

 

There are certainly other plants that we could have put on the list.  Some of the Echinacea coneflowers, for instance, seem rather spiky.  And the European Echinops sphaerocephalus is a real looker.  But hopefully we've listed the most awesome of our St. Louis spiky plants.

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Doesn't Miss Thimbleweed look dainty and innocent as she spins around in her white gown?  Huh!  Don't forget who she is.  She's in the Ranunculaceae.  Anybody related to her Uncle Ranuncle even by a single pollen grain is sure to be bad news.  Take a bite out of her and you might end up with a mouth full of blisters.  Even the deer leave her alone.  She's hard on other plants too.  She uses her acrid protoanemonin oil as an allelopathic potion to inhibit the germination and growth of all those around her.

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LEAF IDENTIFICATION:

Each leaf is compound with 3 leaflets. (See the trifoliate leaves for yourself at MissouriPlants.com.)  The plant has both basal leaves and cauline (stem) leaves.  Each basal leaf has a long petiole (sometimes over a foot long!).  The cauline leaves arise from 1 or 2 whorls along the stem.​  Don't you find that "whorls" (3 or more leaves per node) are easier to see than "opposite" leaf arrangements (2 leaves per node), which in turn are easier to see than "alternate" leaf arrangements (1 leaf per stem node)?

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FLOWERS:

As we mentioned when we discussed other beautiful miscreants like the Rue-Anemones, Thimbleweed's ancestors made their debut during a time when flowers were still trying to figure out how to be flowers.  Modern plants have learned to consolidate their sexual parts and not be such exhibitionists.  But instead of having one sleek and efficient multi-carpellate ovary, Thimbleweed takes up the whole neighborhood with ovary upon ovary stacked on top of one another.  Like the dinosaurs before us, we're tempted to shout "Get yourself together, Thimbleweed!"  But after more than a hundred million years we can probably safely say that shaming doesn't work.

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

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STANDARDIZED FLOWER COMPARISON FORM: (please click for GLOSSARY)

INFLORESCENCE: The inflorescence is usually a solitary flower on a long stalk that grows from an upper leaf axil.

CALYX: There are 5 white, petal-like sepals.

COROLLA: As with other anemones, there are no petals.  Instead there are colored, petal-like sepals.

ANDROECIUM: The androecium is a whorl of 50 to over 70 greenish stamens with yellowish anthers.

GYNOECIUM: The gynoecium consists of a receptacle fitted with many green unfused (apocarpous) ovaries that form a prickly head with slightly curved tips.  These ovaries are positioned superior to the other parts.  

FRUIT: The ovaries mature into achenes as the central receptacle elongates.  Eventually during the winter or following spring, the seedhead will disintegrate and the greyish cottony mass (formed from the styles) will then tumble away in the wind, dispersing its seeds.

 

- Michael Laschober

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