Chaptalia texana & C. carduacea: Anthesis to Dispersal

by Bob Harms 

The published field and pressed specimen observations of the characteristics of Chaptalia flowering heads fail to reflect the complexity of the bloom cycle for C. texana and C. carduacea. Changes that occur during this period involve:

1. the opening and closing of the head during the course of a day (for C. texana: early spring phase);
   
   Day 6 in the bloom cycle of one C. texana head, from 7:07 am to 7:42 pm on February 19, 2011.
   
   
2. the rising and lowering of the head & peduncle during the course of a day, as well as over the much of the bloom/fruiting period;
   
   Rising/Falling on day 5 in the bloom cycle of one C. carduacea head,
   from 6:57 am to 7:27 pm on March 21, 2011.

3. the direction of the head with regard to the primary light source (heliotropism);
   
   Aligning toward the south from bud to day 15 in the bloom cycle of two C. texana heads (Feb. 24 — March 11, 2011).
   
   
4. the exserting of the style branches of pistillate florets relative to the lengthening of the pappus;
   
   Style branches & pappus of the same head on days 1, 3, 5, 7 of anthesis plus day 8 post anthesis (2 views).

5. the exserting of the anther tube and/or style branches of the perfect florets.
   
   Perfect floret details early spring on the left, late spring to fall on the right.
   
   

In hopes of addressing some of these issues the bloom cycle of mature plants for each species was closely monitored during February, March and April 2011. They were maintained in pots, had been kept adjacent since spring 2010, and were briefly protected from a hard frieze during January & early February in a greenhouse. With few exceptions photographs or sketches were made over the course of each day of the bloom head and peduncle from the onset of anthesis until dispersal. The angle of the head & peduncle was recorded each time a change was noted — i.e., the ‘nodding’ behavior. The direction of the head in relation to the sun was also noted — for evidence of heliotropism. In the course of my study I refined my approach as issues became apparent, so that the earliest observations were somewhat less focussed.