PLANT OF THE WEEK

Dr. T. Ombrello - UCC Biology Department

 

POINSETTIA

 

Common name:          Poinsettia  

 

Scientific name:        Euphorbia pulcherrima

 

Explanation of scientific name:       

Euphorbia     - Euphorbus was the Greek physician of King Juba II (about 50 BC to 19 AD) of Numidia (present day Algeria).  King Juba II named a group of newly discovered plants after his physician.

pulcherrima  - pretty, beautiful, handsome

 

In its natural habitat of Central America, the poinsettia is a stiff, open shrub that can easily reach a height of 10 feet, blooming sporadically between November and March.  Like other members of the Spurge family (Euphorbiaceae), including Crown of Thorns, Castor bean, true Rubber trees and Cassava (from which we get tapioca), the poinsettia contains milky latex that discourages plant-eating animals.

Originally used exclusively as a landscape shrub in subtropical climates, the modern era of poinsettias began with a poinsettia seedling grown by a Mrs. Enteman in Jersey City, New Jersey in 1923.  Called “Oak Leaf”, this plant was better suited to pot culture, and its offspring helped the poinsettia to become a popular symbol of the Christmas season along with coniferous trees, hollies, and mistletoe.

When the Christmas holiday season is over, those of us in possession of a poinsettia plant will inevitably ask ourselves:  “What do I do with it now?”  In most cases, the answer is to keep it until you tire of it, and then throw it away.  It was not too long ago that the poinsettia would defoliate and/or die under household conditions soon after the holidays, and would be disposed of shortly thereafter.  But, not anymore.

The poinsettia has come a long way since Joel Poinsett, the first United States ambassador to Mexico, introduced it into our country in 1825.  Plant breeders have produced a plant that is significantly better suited to the indoors in comparison to the original types.  In most cases one gets tired of looking at the poinsettia long before its beauty fades.  Personally, I get tired of looking at mine when I bring home the Easter lilies.  The poinsettia stays in “bloom” so long because the showy “flowers” are not really flowers at all, but are modified leaves called bracts found just below the small, inconspicuous yellow flowers.  Leaves are more long-lived than flowers, and can persist on the plant for many months.

Some gardeners like the challenge of bringing the poinsettia back into bloom the next year.  Although it is difficult to produce a flower shop quality poinsettia at home, it is not too difficult to at least get it to bloom the next winter if one keeps in mind what some of the plant’s requirements are.

Despite its use at Christmas time, the poinsettia is not cold hardy.  In fact, it is damaged by temperatures below 50oF.  Your plant will last longer if you keep it out of drafts from windows and doors.  Other than that, the plant’s indoor requirements for the rest of the winter and spring are straightforward.  Keep the plant in the sun, let the soil dry just a bit before watering it thoroughly, and give it a regular dose of water soluble fertilizer once a month.  Cut back the colored bracts and flowers by late winter and the plant will branch and send out strong shoots during the spring.

After all danger of frost and even cool weather has passed, move the plant outdoors.  Sinking the pot into the soil up to its brim in a sunny garden works fine.  The plant will love our summer and will grow luxuriously.

At this time, a decision must be made.  Do you want to bring this large specimen back indoors to bloom for next Christmas, or would you prefer smaller plants, closer in size to the plant you started with?  If the original plant is to be kept going, keep pinching it back through the summer.  This will not only prevent it from becoming too tall to handle, but will make it bushy and compact.  Smaller plants can be started easily by rooting 3-inch long cuttings in July.  Each cutting will finish off as a nice 6-inch potted plant if pinched in September.  Bring the plants back indoors before temperatures drop into the 40’s in the fall.

Next comes the part where many people go astray.  But first, a little theory.  Poinsettias are short-day plants.  They set flower buds under conditions where the nights are longer than the days.  At our latitude, this occurs in late September.  If the plant receives natural light and dark cycles through October, it will bloom for Christmas.  But, during this time the plants are indoors because of cold weather, and in most homes they are illuminated well into the night by household lights.  This delays the bloom significantly.  Keep in mind that it is difficult to even give away poinsettias on December 26th.  With their red bracts, however, they probably could be used for Valentine’s Day.

To force blooming indoors in time for Christmas, one has several options.  An easy method would be to put the plant in a little used room with a sunny window and no extraneous light at night.  Let nature do the rest.  Otherwise, find a place where the plant can be kept in absolute darkness for 12 to 14 hours every day starting in the beginning of October.  In a closet or under a box will do.  By early November, the new leaves will be coming out red, and you are on your way to a flowering plant by December.  A still popular myth is that poinsettias should be left in a closet for a month.  This will kill the plant!  It needs long nights, but at the same time sunny short days.

Finally, the idea of the poinsettia as a dangerously poisonous plant is also a myth.  Admittedly, some people may experience an allergic reaction to the milky latex that exudes from any cut surface, but there are numerous common houseplants, including philodendron, dumbcane, and oleander, that are considerably more toxic.