Green Antelopehorn photo by bharding81 CC BY-NC

St. Louis is a butterfly heaven!  We've got 14 species of Milkweed!  It was too hard to select just one of these strange and beautiful plants for our Plant-Spotter, so we've chosen 4 of them: 2 for this week (which we're calling the "Spring Milkweeds") and 2 more for a future week (which we'll call the "Summer Milkweeds").  Please click on the various names to study and compare their photos (from MissouriPlants.com). 

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Asclepias amplexicaulis (Clasping Milkweed) / Flowering: April-July

Locations: [STFR]

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Asclepias hirtella (Tall Green Milkweed) / Flowering: May-August

Locations: [CUIV, HUGH]

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Asclepias incarnata (Swamp Milkweed) / Flowering: June-August 

Locations: [BABL, CUIV, GRAM, MERA, ONON, SHAW, STFR]

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Asclepias purpurascens (Purple Milkweed) / Flowering: May-July 

Locations: [BABL, CUIV, GRAM, LITL, MERA, ONON, SHAW, STFR]

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Asclepias quadrifolia (Fourleaf Milkweed) / Flowering: May-July 

Locations: [BABL, CUIV, DONR, GLAS, GRAM, LABQ, LITL, MERA, ONON, ROCK, SHAW, VALV, WELD]

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Asclepias stenophylla (Narrowleaf Milkweed) / Flowering: May-July 

Locations: [GRAM, MERA, ONON]

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Asclepias sullivantii (Prairie Milkweed) / Flowering: June-July 

Locations: [SHAW]

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Asclepias syriaca (Common Milkweed) / Flowering: May-August 

Locations: [BABL, CUIV, DONR, HAWN, LITL, MERA, ONON, SHAW, YUNG]

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Asclepias tuberosa (Butterfly Weed) / Flowering: May-September 

Locations: [BABL, CUIV, DONR, GRAM, HAWN, LABQ, LITL, MERA, ONON, SHAW, STFR, VALV, VICT, WASH, YUNG]

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Asclepias verticillata (Whorled Milkweed) / Flowering: May-September 

Locations: [BABL, CUIV, DONR, GRAM, LABQ, LITL, MERA, ONON, SHAW, STFR, VALV, WASH]

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Asclepias viridiflora (Green Comet Milkweed) / Flowering: May-August 

Locations: [BABL, CUIV, GRAM, LITL, MERA, ONON, ROCK, SHAW, VALV]

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Asclepias viridis (Green Antelopehorn Milkweed) / Flowering: May-June 

Locations: [DONR, HAWN, MERA, SHAW, STFR, VALV, VICT, YUNG​]

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Cynanchum laeve (Honeyvine Milkweed) / Flowering: July-September 

Locations: [BABL, CUIV, DONR, GRAM, HAWN, MERA, ONON, ROCK, SHAW, STFR, YUNG]

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Matelia decipiens (Climbing Milkweed) / Flowering: May-June 

Locations: [DONR, GRAM, HAWN, LABQ, LITL, MERA, ONON, POWD, SHAW, STFR, VALV, WASH, YUNG​]

In case you'd like to visit all 14 of them this summer, we've listed some of the locations where they've been spotted.  (If you find them in other natural areas, please let us know so we can update our list.)

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- THE CLIMBING MILKWEED -

Matelia decipiens

Look at the top photo above.  What horrors might these terrified folks be running away from with their arms flailing in the air?  And what is that tiny jewel in their bellybuttons?  Welcome to the strange world of the milkweeds!  This is one of the 2 milkweeds we're supposed to find this week.  But if we want to see these Gumby-like folks in action, we'll need to hurry because their flowering season will soon be over. 

Climbing Milkweed (also known as "Deceptive Spinypod") doesn't have the horn and hood that some other milkweeds have, but it's a true milkweed complete with a gynostegium.  

Besides its weird looks, another good reason to learn about this plant (and maybe even grow it in your garden) is that it's in some existential trouble.  The states on both sides of us, Illinois and Kansas, have designated this plant as "Critically Endangered". 

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St. Louis has one other climbing milkweed, "Honeyvine Milkweed" (Cynanchum laeve), but it won't be in flower for another month or so.  It's interesting that neither of our climbers (Metelea decipiens, Cynanchum laeve) is in the Asclepias genus.  

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- THE GREEN ANTELOPEHORN -

Asclepias viridis

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The name alone makes it worth putting on this week's Plant-Spotter list.  And look at the flowers!  It's hard to believe it's even in the same family as the Climbing Milkweed.  Once again, if we want to see this floral masterpiece with our own eyes, we'll need to hurry because it won't be in bloom much longer.

If you've never met Asclepias viridis, the pleasant fellow in this VIDEO (12:06) will be happy to introduce you.  It's not the shortest video because the presenter (a 4H leader) tends to ramble.  But the ramblings of a knowledgeable person can be worthwhile.

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Isn't the name "Antelopehorn" quite enough?  Why add the word "Green"?  It's to differentiate him from his twin brother in Texas who really is just called "Antelopehorn" (without the "Green").  Here's a handsome (and very informative) silent VIDEO (2:47) starring this brother, Asclepias asperula, with closeup views of him being pollinated.  It's short, but you'll have to pause it often to read the important captions about "pollinia" (sticky yellow pollen sacs).

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You'll notice that we have 3 species of Milkweed whose species epithet begins with the letter "v".  It might take some effort to avoid getting them confused.  Since the Latin "viridis" means "green", we should probably add a 4th species to our "do-not-confuse" list: Asclepias hirtella, the "Tall Green Milkweed".  

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- MILKWEEDS IN GENERAL -

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The Milkweed Family has taken an evolutionary turn that other flowering families haven't.  Some of their flower parts have melded together to create different kinds of structures.  For example, their stamens (a male reproductive part) and stigmas (a female reproductive part) have fused to form a "gynostegium".  In order to keep up with this innovative family, we'll need to learn a few new terms.  In addition to "gynostegium" there are a few others such as "pollinia", "corona", "horn" and "hood".

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The internet offers a wealth of illustrations and explanations that will give us a clear understanding of these new flower structures.  Here are some links that seem quite helpful:

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GYNOSTEGIUM (an illustration)

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CLASPING MILKWEED FLOWER (a labeled photo)

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HOW TO IDENTIFY MILKWEED (a silent video [2:47] by the Florida Native Plant Society)

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CORONA (an illustrated explanation)

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WAYNESWORD (scroll down to Milkweed)

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BUTTERFLY WEED VIDEO (from the "Summer Milkweeds" Plant-Spotter article)

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We're so lucky to have 14 different milkweed species in St. Louis.  We'll continue this exploration in a couple of weeks when the Summer Milkweeds will be in bloom.  But in the meantime, don't forget to look for Metelea and the Green Antelopehorn before it's too late!

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- Michael Laschober