Senecio flaccidus [Threadleaf Groundsel]

[Andrea B.]

Blum, A.G. (2021) Senecio flaccidus Less. (Asteraceae) [Threadleaf Groundsel] Flowers photographed in ultraviolet, infrared and visible light. https://www.ultravio...leaf-groundsel/

 

La Secuela, Eldorado at Santa Fe, New Mexico, USA

02 July 2020

Wildflower

 

Synonyms:

• Senecio longilobus Benth
  
• Senecio filifolius (L.) Hook.
  
• Senecio douglasii DC.
  
• Senecio monoensis Greene
  

Other Common Names:

• Threadleaf Ragwort
  
• Douglas Senecio
  

.

Comment:

Of the gazillions of Senecios growing in the Western US, Senecio flaccidus was a good one to learn on because it is abundant and easily keyed. The early summer plants dried up (in summer of 2020) into hundreds of white fluff-balls, but new plants bloomed again in the late summer/early fall.

In UV light the flower has a UV-dark disk and UV-bright rays. See more comments in the photo captions below.

 

References:

1. Allred, Kelly W., Jercinovic, Eugene M., Ivey, Robert DeWitt (2021) Flora Neomexicana III: An Illustrated Identification Manual, Second Edition, Part 2, Senecio, Packera Key, page 196. Print on demand at lulu.com.

2. Finley, Willa F., Nieland, Lashara J. (2013) Land of Enchantment Wildflowers. Threadleaf Groundsel, page 69. Texas Tech University Press, Lubbock, Texas.

3 Littlefield, Larry J., Burns, Pearl M. (2015) Wildflowers of the Northern and Central Mountains of New Mexico. Threadleaf Groundsel, page 160. University of New Mexico Press, Albuquerque, New Mexico.

 

4. SEINet Arizona-New Mexico Chapter (acc 16 Feb 2021) Senecio flaccidus Less. This is a southwestern biodiversity organization making use of the Symbiota portal software.

5. Southwest Colorado Wildflowers (acc 16 Feb 2021) Senecio flaccidus. Website published and maintained by Al Schneider and hosted by Rocky Mountain Biological Laboratory

6. Wildflowers of New Mexico (acc 16 Feb 2021) Senecio flaccidus. Website published and maintained by George Oxford Miller.

 

 

PHOTOS

 

Visible Light [f/8 for 1/200" @ ISO-80 in Sunlight with Nikon Z7 + Nikkor Z 24-70/4.0S]

This S. flaccidus growing a few feet from my driveway had no problem growing up through those rocks.

 

 

UV/IR Equipment [Nikon D610-broadband + Nikon 105mm f/4.5 UV-Nikkor]

 

Visible Light [f/16 for 1/13" @ ISO-200 in ambient window light with Baader UVIR-Block Filter]

The Senecio flaccidus heads around here usually have 8 rays.

 

 

Visible Light [f/16 for 1/2.5" @ ISO-200 in ambient window light with Baader UVIR-Block Filter]

The linear leaves look almost succulent.

 

 

Ultraviolet Light [f/16 for 15" @ ISO-100 with SB-14 UV-modified Flash and BaaderU UV-Pass Filter]

Long exposures were made for the UV photos to enable 2 flashes in different positions for better lighting coverage. It was not, however, a good idea to UV photograph a floral subject with UV-dark parts against a black music stand. Lesson learned.

The disk florets and reproductive parts are all UV-dark. A few dark streaks on the rays are the result of minor damage and are not part of the UV-signature. Bits of pollen, dust and spider webbing are all UV-bright.

 

 

Ultraviolet Light [f/16 for 10" @ ISO-100 with SB-14 UV-modified Flash and BaaderU UV-Pass Filter]

The wooly hairs on the involucre and stem are UV-bright.

 

 

Ultraviolet Light [f/16 for 5" @ ISO-100 with SB-14 UV-modified Flash and BaaderU UV-Pass Filter]

UV-dark veining is quite obvious on the abaxial side of the ligules. On the top side of the rays this veining is very faint. Here in this view you can see very small bractlets under the involucre which are almost not noticeable in visible light.

 

 

Infrared Light [f/16 for 1/1.6" @ ISO-200 in ambient window light with B+W 093 IR-Pass Filter]

There are a few Asteraceae which have some IR-dark disk structures, but S. flaccidus is not one of those.

[Andrea B.]

Notes to Self

 

Asteraceae, page 83.

Key F. Ray flowers present; pappus of capillary bristles, at least in part. YES.

Key F.1. Ray corollas yellow, orange, or red. YES.

Key F.1.27. Leaves alternate. YES.

Key F.1.27.30. Phyllaries in 1-2 series, equal in length, often subtended by smaller calyculi. YES, looks like 1 series.

 

Key F.1.27.30.31. Annuals, herbaceous perennials, or low sub-shrubs (woody only at base).

Key F.1.27.30.31. Leaves less than 8 cm wide and not suborbicular or ovate. Go to Senecio.

OR

Key F.1.27.30.31. Shrubs, obviously woody well above the base.

Key F.1.27.30.31.33. Leaves linear and evenly distributed on stem. Go to Senecio.

 

So we are going to Senecio on page 196 where a key for Senecio and Packera is presented.

 

1. Plants shrubs, woody at least at the base, or coarse bushy, shrub-like plants with linear leaves 1-3 mm wide.

I definitely have those kind of leaves, although I'm not sure about the shrub-ness of my plant.

The other choice doesn't seem to lead to anything with linear leaves.

 

1.2. Leaves of leaf lobes linear, 1-3mm wide. YES.

1.2.3. Herbage prominently tomentose. YES, looks wooly to me.

1.2.3.6. Plants 40-120 cm tall or more;

leaves evenly distributed, seldom recurved; variety of soils and habitats.

YES, my leaves not clustered at stem ends and not recurved. Senecio flaccidus.

 

Note that in this Key you can also take a glabrous trip to Senecio flaccidus var. monoensis.

 

Page 202 Senecio flaccidus Lessing [Threadleaf Groundsel]

• shrub or subshrub. (I'd say subshrub if I had to choose.)
  
• taprooted but taproots forming woody crowns.
  
• stems 30-120 cm tall, glabrous or lanate-tomentose. (mine lanate-tomentose)
  
• leaves sessile or obscurely petiolate.
  
• leaf blades linear to filiform, entire, toothed, or pinnatifid, 3-12 cm long. (mine entire)
  
• heads radiate, 1-20 in corymbiform clusters, often comprising larger, showy arrays.
  
• calyculi of 3-5 bractlets conspicuous to half the length of the phyllaries or inconspicuous, sometimes lacking. (mine inconspicuous)
  
• phyllaries 13 or 21+, tips green or black. (for mine the tips are yellowish but the tippy-tips are indeed dark)
  
• ray florets 8 or 13, sometimes 21. (for mine 8)
  
• corollas yellow or sometimes whitish-yellow.
  
• ligules 10-20 cm long. (well, no. That would be one huge Senecio head!)
  ERROR: should be 10-20 mm.
  Flora of N.A.: corolla laminae 10–15(–20) mm.
  
• achenes hairy.
  

Herbage usually tomentose; bractlets subtending the phyllaries minute or absent; involucres cylindric or campanulate => var. flaccidus. YES. Throughout the state. Hills, plains, bajadas, dry mountain slopes, canyons, arroyos, mesas.

 

Herbage tomentose to glabrous; bractlets subtending the phyllaries well-developed, involucres campanulate => var. monoensis. Desert plains and canyons. Hidalgo Co. in New Mexico. NO.

[Andrea B.]

Finished 16 Feb 2021 5:56 PM MST GMT -7