The Secret Life of Poinsettias

poinsettia hedge in Culver City

poinsettias on Camarillo Springs Road

“The Secret Life of Plants” was a popular book published in 1973 which made seemingly outrageous claims that plants respond to stimuli in human ways.

Plants would grow better when soft music, as opposed to loud, was played in their vicinity and they positively flourished when gardeners spoke to them in tender loving tones.  Plants were hooked up to polygraphs and responded to the thoughts and threats of researchers in seemingly appropriate, if paranormal, ways.   Plants, supposedly, could also feel pain and communicate with one another. Although most of the reports in this book were debunked as pseudoscience, there has been evidence, of late, that plants do have the capacity to inform each other of what is going on around them in a caring spirit.  For example, bean plants that grow up in close proximity to one another begin to form chemicals that attract aphid predators such as ladybugs when one of their number is exposed to a pack of aphid pests.
Bacteria Responsible for Compact Growth of Poinsettias
I thought about the secret life of plants when looking into the history of commercial poinsettia production.  It was fascinating to learn that the multi-branched growth habit we take for granted in these plants is the result of a phytoplasma infection.  A phytoplasma is kind of bacteria, lacking cell walls, that is normally pathogenic.  It is a phytoplasma that causes witches’ broom in certain woody plants, a condition characterized by tight clusters of stems and leaves, often taking on the appearance of a bird’s nest, and which is typically fatal, as in the case of citrus, to the tree.  It should be noted that when witches’ broom is not caused by a phytoplasma, as in the case of oak and peach trees, conifers and roses, where the disease agent is a fungus, an insect, a spider mite, or even a virus, the condition is usually not life threatening and you need only remove the distorted growth as a control measure.
Bacteria Determine Hormonal Balance in Poinsettias
The effect of a phytoplasma in any plant is to upset the hormonal balance.  This results in branching or compact growth on plants whose natural growth habit is more vertical.  In their habitat of Mexico and Guatemala, poinsettias are weedy plants exhibiting rank vertical growth to a height of thirteen feet.  It took the Ecke family to discover the secret to turning this gangly weed into the most popular potted plant in the world, with 100 million sold world wide between Thanksgiving and Christmas each year. The Eckes had employed the phtyoplasma branching agent without even knowing it, as will be explained below.
The story of the poinsettia has a cinematic, rags to riches, quality and, ironically enough, had its origins in Hollywood.  In 1900, Albert Ecke, destined to become the patriarch of the poinsettia industry, was on his way from Germany to Fiji, where he had plans to open a health spa.  Stopping along the way in Los Angeles, he took such a liking to the area that he decided to settle in Eagle Rock, where he became a dairy farmer and planted an orchard.  Ecke noticed the popularity of the poinsettia plant — its bright scarlet bracts, to be precise — and started selling it on street corners.  He would soon plant five acres of poinsettias in Hollywood and began shipping the colorful stems cross country during the Christmas season, creating an association between the plant and the winter holiday.
Secret to Dwarfing Elongated Plants 
But Ecke was dissatisfied with the poinsettia’s elongated growth and decided to experiment with modifying it.  He had learned how to dwarf the growth habit of plants from a neighboring gardener back in Germany and applied this technique to developing new poinsettia cultivars.  The procedure involved grafting brightly colored poinsettia shoots from elongated plants onto multi-branched poinsettia grown from seed.  The elongated shoots would soon start to branch under the influence of the branched seedlings.  It wasn’t until the 1990’s that a botanist from the USDA  would divine the secret of turning elongated poinsettias into compact plants, namely the presence of a phytoplasma bacteria in the sap of branching plants which would migrate from the sap of the seedling rootstock into the sap of the grafted scion shoot, encouraging it to branch.  This phytoplasm organism would continued to live in cuttings cloned from the grafted plants, explaining Ecke’s ability to mass produce multi-branching and compact poinsettia cultivars.  Conclusive proof of the bacteria’s influence on branching was demonstrated by application of antibiotics to branched poinsettia plants.  Soon after the antibiotics were circulating in the compact, multi-branched plants, branching ceased and all you got was elongated growth.
I was prompted to investigate poinsettias after receiving an email from Al Basiulis, who gardens in San Pedro.  Basiulis was wondering about a stand of poinsettias that were eight feet tall when he first moved into his San Pedro home twenty-five years ago.  Some of the plants had died and he wanted to know if there was a way to keep the others from meeting a similar fate.  I learned that the plants were not receiving as much sun as they once had due to growth of a nearby lemon tree and that his soil was a heavy clay.  Insufficient light and imperfect soil drainage make it difficult to grow poinsettias.  Basiulis is to be congratulated that he succeeded in keeping his plants growing all this time.
How to Grow Poinsettias from Cuttings and from Seeds
Tip of the Week:  There are two times of the year when you can propagate your poinsettia from cuttings. When the little yellow flowers in the center of your poinsettia bracts — those brightly colored leaf like appendages — begin to fade in February or March, you can propagate your plant by detaching six to eight inch stem cuttings.  You would want to do this pruning in any case once your poinsettia goes dormant.  After dipping the cuttings in root hormone, insert the bottom third of the cuttings in a fast draining sterile soil medium consisting of half sand and half perlite or half sand and half vermiculite.  Alternatively, you can wait until weather warms in spring or even summer when shoots start to sprout from the base of your plant that you received the previous winter.   Detach these small three to four inch shoots and give them the same treatment described above for the longer shoots.
You can also propagate poinsettias from seed.  To produce the fruits or pods in which poinsettia seeds are found, take a cotton swab and dab it on the pollen that forms on the tiny yellow flowers before they fade.  Brush the pollen onto other flowers or onto the same flower from which the pollen came since each poinsettia flower contains both male and female parts and the flowers do self-pollinate. After the seed pods form and the plant begins to enter dormancy as its bracts fade, remove the green pods and place them in a paper bag.  When pods turn brown and dry, remove the seeds and place them in a sandwich bag filled with a 50:50 mix of moist sand and peat moss and put them in the refrigerator for three months.  You can then plant the seeds one inch deep in a fast draining soil mix and you should see them sprout within three weeks.

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