Journal archives for March 2018

March 05, 2018

"coreopsis and friends"

So, I just found out that the tribe Coreopsideae has as it's common name "coreopsis and friends".

Posted on March 05, 2018 22:13 by nathantaylor nathantaylor | 6 comments | Leave a comment

March 24, 2018

Texas species of Dandelion, as near as I can tell

According to Flora of North America, there are two species of Dandelion (Taraxacum) in Texas: T. officinale and T. erythrospermum. Apparently, the only way to tell the two apart is by the color of the achenes. Taraxacum officinale has fruits that are "straw-colored to olive, brown, or red to pale or dark gray" while T. erythrospermum has fruits that are "brick red to reddish brown or reddish purple". What follows are some photos of what I believe are representative of both species.

Taraxacum officinale at left, Taraxacum erythrospermum at right.

Fruits in greater detail:
Taraxacum officinale:

Taraxacum erythrospermum:

I have always been dubious of colors as key characteristics and learned early on not to trust them. I have since learned there are some circumstances, but I remain dubious here. At the very least, it seems like there might be some structural characteristics here that would be much more stable that could be relied upon. In the previous photos, T. erythrospermum seems to be smaller on average (this was the largest achene I could find from the specimens I took), be less hairy, and be muricate throughout (the rough horn-like projections). Taraxacum officinale, on the other hand, seems to have minute hairs (contrary to the description) and be muricate only towards the apical end. There is also, of course, a color difference. In the plants themselves, T. officinale has a tendency to have harier peduncles in the environment these were encountered in.

This is admittedly a very small sample size and I will try to follow-up with more info. Ideally, I would grow the two species and see how well they retain their parents' tendencies. Color is usually such an unstable characteristic that I'm still not convinced (as is leaf shape, the other characteristics used). Not only that but there is overlap in the description itself.

Another good, and more striking, comparison photo of the two can be found from Maryland Biodiversity Project and is displayed below:

I tend to think this comparison represents the extreme end of the variability of the two species and identification of other individuals is not usually this easy.

Observations the photos are found in are as follows:
Taraxacum officinale:
Fruiting head. Single achene.
Taraxacum erythrospermum:
Fruiting head. Single achene.

Reliable T. erythrospermum observations:
https://www.inaturalist.org/observations/7811183
https://www.inaturalist.org/observations/7766362
https://www.inaturalist.org/observations/7731039
Reliable T. officinale observations:
https://www.inaturalist.org/observations/9577717
https://www.inaturalist.org/observations/9402362
https://www.inaturalist.org/observations/9292763
https://www.inaturalist.org/observations/9244265
https://www.inaturalist.org/observations/9166812
https://www.inaturalist.org/observations/9064497

Posted on March 24, 2018 01:25 by nathantaylor nathantaylor | 30 comments | Leave a comment