Saturday, June 28, 2008

A Multitude of Milkweeds

For some reason, I'm enamored with milkweeds. It probably started with their cachet as food for the caterpillars of monarch butterflies. All schoolkids learn about monarchs, I think, and most learn to love them. I know I did.

Then I discovered that milkweeds host an entire community of milkweed-specific insects, adapted to eat their poisonous tissues. Because these insects feed on milkweeds, they taste terrible and may even be poisonous in their own right. This means that few animals want to eat them. Not surprisingly, the milkweed eaters boldly advertise their untasty status with bright colors.

The final building block in my love affair with milkweeds was discovering how many of them have extremely fragrant flowers. I'm talking the kind of fragrance you drink in from several feet away, wondering, "What's that lovely smell?" Add in cool seed pods, pretty blooms in many species, and what's not to love?

So it's been fun to discover that we have several species of milkweeds on our property.

The first milkweed species we found was green antelopehorn, Asclepias viridis. Its flowers are neither showy nor fragrant, but the plants possess a certain quiet appeal nonetheless. They increase in overgrazed pastures. We have a lot of them.

Next I realized that we had a plant or two of common milkweed, Asclepias syriaca. Ironically, I've discovered that this species is the least common of the milkweeds that occur on our 10 acres. One of the taller, upright milkweeds, common milkweed has large, pretty pink pom-poms of fragrant flowers. Personally I think it would be a lot more popular with a less "common" common name.

I identified both of these 2 species shortly after we moved in. The third species was visible last year, but I didn't look at it closely enough to realize that it was different from the common milkweed. It's growing on the west banks of the draw in a small, loose colony of about 20 individual plants. (At least I think they're individuals. I haven't uprooted any to see if they are connected by underground rhizomes.) Another upright, pink, fragrant bloomer, it's known as showy milkweed, Asclepias speciosa. Its blooms are composed of fewer flowers than those of common milkweed, and they look "spikier". The leaves also tend to be held a little more upright than those of common milkweed.

About 20 feet away from the showy milkweed colony, back up on flatter land, I noticed a group of upright milkweeds this spring that didn't bloom as soon as the nearby showy milkweed or the further away common milkweed. Sure enough, when they did bloom they were a 4th species called smooth or Sullivan's milkweed, Asclepias sullivantii. Again they are pink and fragrant, but their odor is different, reminding me of cloves. Note that their flowers are not as "spiky" as the showy milkweed's, and their stem is smooth.

Backing up a bit, a month or so ago as the green antelopehorn was starting to bloom, I noticed a few scattered, smaller individual stems of what looked like milkweed, but it wasn't blooming. I marked several of them with orange flags and I've been monitoring them to see what they are. About 2 weeks ago, they started to bloom with odd little clumps of greenish-white flowers. Shown here to the right, the flower is on the lower left, the buds are on the right. I'd never noticed any milkweeds like these before but, in looking them up, I've learned that they are called green milkweed, Asclepias viridiflora. Chalk up another species that "magically appeared" after burning.

Finally, when I was out trying to get a decent photograph of the green milkweed, I noticed a singleton plant with much finer leaves and slightly different flowers. The flowers were still greenish-white, but they weren't as pendulous as those of the green milkweed. The overall effect of the plant was daintier, if taller. This turned out to be narrow-leaved milkweed, Asclepias stenophylla. As closeups of its flowers show, it's probably the least showy of them all (although the green milkweed is a close second), but I'm still glad to find it on our prairie.

I'm still waiting for the prom queen of the milkweeds, the orange-flowered butterfly milkweed or Asclepias tuberosa, to show up, but so far I haven't seen any sign of it. No luck finding swamp milkweed, Asclepias incarnata, or the endangered Mead's milkweed, Asclepias meadii, either. (Not that I think there's the slightest chance of finding the latter on this property, but one can always dream!!!) There are a few other species that are possibilities, but meanwhile I'm enjoying my embarrassment of milkweed riches with the 6 species I have found.


Steve said...

Gaia gardener,

I am pleased to find another milkweed fan. I am a KU graduate student doing community ecology research on Mead's and other milkweeds, including work on insect herbivores. A note on Mead's: you will not find it on your property because it is only found on virgin prairies from Shawnee County eastwards.

Gaia gardener said...

I knew that the chances of my finding Mead's milkweed on this property were nil, but I didn't realize that we weren't even within its range. That's good to know.

Later last summer, I found 2 more milkweed species on the property. Pictures and a little info were posted in an entry at that time ( I'd be curious to know if I identified the plains milkweed correctly.

Good luck with your research!

Steve said...

I think your IDs or A. incarnata and A. pumila are correct. I don't think we have pumila in NE Kansas but all the online photos I checked out point to that species and not verticillata. My main field site, a native prairie owned by KU has 10 Asclepias species. Question for you: Have you ever seen this insect:

R. lineaticollis normally feeds on common Asclepias species like syriaca and viridis but I have also found it attacking meadii frequently. It can kill the above ground stems with ease so it is of great interest to me.

Gaia gardener said...

I have noticed a "sudden death" syndrome in isolated individuals of my A. viridis, especially in our back 5 acres, but I haven't made any effort to chase down the source since they are so common back there. While I haven't noticed any beetles that look like R. lineaticollis, I will start inspecting my milkweeds more closely and let you know if I see any. Can you tell me a little more about its mechanism of action? Would it still be on plants that were turning yellow and beginning to obviously decline? Is it normally found on the top or bottom surface of the leaves? Is it only found on Asclepias? Are there other known causes for a "sudden death" syndrome in A. viridis?

I hadn't walked my back acreage for several weeks until this morning. One interesting thing I noticed that is possibly of value here was that my thriving colony of showy milkweed from last year does not appear to have surfaced at all this year. It bloomed well last year (although it did not appear to set any pods/seed) and I did not notice any signs of decline or disease before it went dormant late last summer/last fall. We have neither mowed nor burned the area this year (which may be part of the problem). I was rather lamely hoping that it was just having a less productive year. Now you've got me concerned.