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Flowering of Chlorogalum Pomeridianum (Soap Plant)

By Patrick Pizzo, Chapter Member, June 2007

The neighbors thought I was already 'nuts', walking a toy wagon loaded with 2-liter  water bottles around our development and hula-hoeing weeds along a 0.6 mile stretch of  City park-strip! After the last few nights, I think I confirmed this conclusion.

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When I began my California Native Plant (CNP) Project along the Guadalupe Creek (a  0.6-mile stretch near the intersection of Camden and Coleman in San Jose, planted with  128 Quercus agrifolia and 200-plus interspersed native plants and shrubs), I came across  Chlorogalum pomeridianum, the soap plant.  I found several plants growing under very hot  and dry conditions in Capitancillos Meadow and they seemed to thrive.  So, one fall,  permits in hand, I transplanted a few soap plants to the project.  One thrived; and
toward the end of May on an afternoon walk, I noticed a 4-foot tall blossoming  inflorescence.  The flowers are white and very graceful in appearance.  On my morning  walk earlier that day I was sure that the flowers had not been present.

I recalled reading about the soap plant in my CNP reference books and on the Internet.   In the back of my mind was something about the unusual blooming of this plant.  One source said that the soap plant only bloomed on a night of the full moon!  I had to
check things out.

I re-read sources and most remarked that Chlorogalum pomeridianum flowered late in the  afternoon.  So, I took a portable chair, a notebook, a digital camera and a good mystery  book and visited my soap plant.  I set up by the plant and began observing and being
observed.  "Call the nut-patrol!"

Prior to 6:00 p.m., only the tall stalk shown, with panicle inflorescence with closed,  bell-shaped flower capsules and some fruit capsules at the base of each panicle.  [Tony  Corelli I hope I am using the wildflower workbook correctly!]  The wavy leaves at the base of the plant were already dry.  The stalk raises about four feet above the buried  bulb.

Just as the sun began to set above the top of the riparian zone along Guadalupe Creek, flowers began to open.  It was 5:45 p.m. when the first flower bloomed.  Prior to that day, flower openings had occurred as evidenced by fruit capsules present at the base of the panicle array.  Un-bloomed flower capsules were present above existing flowers.  To  my amazement, 35 flowers opened in a span of less than one hour each taking about 20 to 30 seconds to open!

About 15 minutes after the first flowers began to appear, two black solitary bumblebees arrived. Each day they visit many of the Capitancillos plants (especially the wooly bluecurls and salvias), but I was surprised they discovered the soap plant flowers so
soon after opening!  Did they know to visit at that time from prior flower-openings of the plant?  Do the flowers give off an 'attracting' scent?  Was it just chance?   I have no idea.

The bees visited each of the 35 flowers.  During their visit, I noticed the anthers (at the tip) went from orange to yellow.  I think there was some type of 'protective' piece, orange in color, initially covering each anther.  This coating either dropped on its own, or the bees or wind helped expose the pollen.  As the bee-visit progressed, there was less and less 'yellow' to the anthers, the pollen having been transferred to the bees!

About sunset, I observed little to no more change in conditions; and bees were about one-hour gone.  Do moths come in the evening hours? How long do these beautiful white flowers stay open?  What happens to the petals?  I could not find fallen petals at the base of the plant.

To help answer these questions, I returned to the site after dark. At 10:00 p.m., the flowers were still open; but by midnight, they were 'closed.'  Yes, that is right.  They don't drop off: they zip up again!  The pistil has been 'activated' and so begins the process to transition to a fruit.  The petals close about the pistil and begin to twist and curl to make a nice 'wrap' for the fruit capsule. Some fruit at the base of the inflorescence, by my observation, had already fallen to the ground!  Perhaps these were the flowers that did not successfully pollinate.  If this is the case, there was about a 70% or better success rate in the production of fruit.

After about ten days, the flowering process was completed.  You could set your watch by the opening of the first flower: 5:45 p.m.!

What a magnificent process!  It was a gas to see this occurring in such a short time.  From just before 6:00 p.m. to midnight, flower bloom and pollination had been completed! Each evening it was kind of like watching a Venus fly-trap open, but in slow motion!

Yes I took photos.  It was kind of windy though around late afternoon.  Taking close-ups of the process was trying. Nevertheless, I think I captured the essence of the flowering of this wonderful and useful CNP!

Patrick P. Pizzo

P.S. the location is along Capitancillos Drive between Pam and Dorcey.  Blooming began Memorial Day Weekend and continued through June 10th, 2007