The Aster Family (part 4)

20150616-20150616-_dsc0028

 

Tragopogon (goatsbeard) species (I think)

 

 

Each floret of a composite family plant produces a single fruit (which contains a single seed) called a cypsela. In many texts and on-line sources, the term achene is used. The difference between the two is technical (it depends on the position of the ovary), and for years both were used rather loosely. While trying to make sense of this I tripped over an article in the Brazilian Journal of Botany, the poorly translated abstract for which reads

The worry about the indiscriminate use of the terms cypsela and achene for the fruits of Asteraceae has been frequently detached by specialists in this family. The present work was developed aiming to verify the existence of arguments to justify the adoption of a term against the other. After historical and anatomical analysis, we concluded that there is technical basis to consider cypsela and achene as different types of fruits. For Asteraceae, the correct is to call cypsela; achenes are only derived from superior ovaries, as in Plumbaginaceae.

At any rate, picture a single small seed with a tuft of hairs, like dandelions have.

20140923-dsc_0115

 

Erechtites hieracifolius (pilewort)

 

 

That’s pretty much it, unless there are barbs instead of hairs:

20141006-dsc_0088

 

Bidens bipinnata (Spanish needles); note the capitulum (flower head) with yellow ray and disk florets at top, another flower head showing the phyllaries in the middle, and the barbed cypsela at the lower right

 

 

next: lower classifications

Flower of the Day: Carolina Elephant’s Foot

Elephantopus carolinianus; Asteraceae (aster family)

20140821-DSC_0201

If you’ve been following my blog you’re probably wondering why this plant is placed in the aster family.  Doesn’t look anything like an aster, does it?  Look closely at the inflorescence; what you’re seeing is four individual disk flowers, each with a 5-lobed corolla.  No ray flowers.  Pretty neat!

I first encountered Carolina elephant’s foot when we moved to our current house.  It was growing as a lawn weed (the foliage is pretty distinctive); I let a small patch of it bloom in order to identify it.

It’s all over the place along the C&O canal, blooming from July to September, but it’s endangered in Pennsylvania and New Jersey (the northernmost part of its range). It can be found south through Florida and as far west as Texas.

20141021-_DSC0007

Here’s what it looks like in mid-October, gone to seed.

A Few Statistics, Illustrated

Depending on when you look it up, and the current state of research, and the seeming whim of taxonomists, the Asteraceae is the largest plant family on Earth, with 23,000 species (more or less).  Only the orchid family is as large, or larger, maybe.  Species in the Asteraceae can be found in almost every habitat, on every continent except Antarctica.

20140518-DSC_0092 Erigeron philadelphicus (common fleabane)

 

 

 

 

In the Potomac Gorge area, I’ve found more plants in the Asteraceae than any other family, by far: seventy species. That’s out of a total of 351, or just shy of 1 in 5.  This includes the asters themselves, the beggar-ticks, bonesets, coneflowers, coreopsis, dandelions, elephant’s foot, everlasting, the various fleabanes, the multitudes of goldenrods, leafcup, hawkweeds, horseweeds, ironweed, fireweed, rattlesnake weed and ragweed and ragwort, pussytoes, snakeroots and sneezeweed, sunflowers and thistles, and wingstem. And some aliens I didn’t bother to name.

20140828-DSC_0072

The second largest family, at 21 species (13 native, 8 alien), was the Fabaceae (pea family).

Lespedeza virginica (slender bush-clover)

 

 

 

 

 

20140613-DSC_0096

In third place was the Lamiaceae (mint family) at 16 (11 native, 5 alien).

Scutellaria elliptica (hairy skullcap)

 

 

 

 

 

lyre-leaved rock-cress

Brassicaeae (mustard family) checked in at 15 (7 and 8).

 Arabis lyrata (lyre-leaved rock cress)

 

 

 

rue anemone duo

 

Ranunculaceae (buttercup family) had 14 (10 and 4).

Thalictrum thalictroides (rue-anemone)

 

 

swamp dewberry

 

The Rosaceae (rose family) had 12 (9 and 3).

Rubus hispidus (swamp dewberry)

 

 

sweet cicely closeup 2

 

And the Apiaceae had 10 (6 and 4).

Osmorhiza claytonii (sweet cicely)

 

 

 

20140729-DSC_0143

And though the Orchidaceae is so large worldwide, in this area I found only two. More on that tomorrow.

Tipularia discolor (cranefly orchid)

 

 

 

Here’s a nice tutorial on the Asteraceae.

Flower of the Day: Short’s Aster

Symphyotrichum shortii; Asteraceae (aster family)

20140929-DSC_0003

Some things to consider when trying to identify asters:

  • size of flower head
  • number of ray flowers
  • number of disk flowers
  • color of flowers (not as important as you may think)
  • shape and size of leaf, including the leaf base and leaf tip
  • leaf margin
  • arrangement of leaves on the stem and whether they’re more or less consistently sized
  • shape, size, color, and number of rows of phyllaries (bracts)
  • presence of glands
  • smoothness (or not) and color of stems

…you get the idea.  Actually this is a pretty general list, but with almost 90 species of Symphyotrichum found in the US (about two dozen in this area), you really have to pay attention to details.

All of which is to say, I’m not always sure I’ve correctly id’d all the asters I’ve been posting about.  But they sure are pretty.

20140929-DSC_0018

Flower of the Day: Frost Aster

aka hairy aster, awl aster; Symphyotrichum pilosum; Asteraceae (aster family)

20140929-DSC_0221-2

So far this year I’ve found 19 different species of aster (Symphyotrichum or Eurybia). I haven’t managed to identify them all, but they are clearly different from each other. This one, though, I’m pretty sure of.

20140929-DSC_0214

Note the characteristically hairy stem in the photo to the right.

Frost aster is another native found in eastern North America (from Texas through Quebec). It grows up to three feet tall in full sun and moist to dry conditions.  I found this specimen growing out of the cracks along one of my favorite rocky bluffs upstream of Carderock.

20140929-DSC_0228