Plant of the Week
Pencil Cactus, Milkbush
Latin: Euphorbia tirucalli
As my wife drove me to the hospital, I decided I must not be dying because I
saw neither a flashback of my life’s many regrets nor the infamous bright light
at the end of a dark tunnel.
But, as scary as barely being able to breathe is, an up-close-and-personal
experience with a poisonous plant was very educational. The plant, pencil cactus
(Euphorbia tirucalli), was the culprit in this late-night adventure.
Pencil cactus is not a true cactus but a member of the Euphorbia family from
tropical parts of Africa and India. In nature, it grows as a 30-foot tall,
leafless tree with pencil-size green branches that function in photosynthesis.
Tiny leaves appear at the ends of new branches when new growth occurs, but they
Pencil cactus is grown as a large houseplant that reaches ceiling height when
given a couple years in a good size container. Plants usually have a narrowly
upright form with branch tips that begin to droop as the plants gain size. I’ve
never seen it flower.
Now for the bad news. One of the common names for this Euphorbia is Milkbush,
a well deserved name. Like all members of the Euphorbia family, milkbush
produces the familiar white latex when the stem is cut, but none in my
experience produce the copious amounts of sap that this succulent produces. The
toxic component found in the sap are thought to be diterpene esters.
My problems began when I stopped by the greenhouse to take a bunch of
cuttings from this interesting plant for an upcoming plant sale. I managed to
get sap spread all over my hands and near one eye.
Symptoms of an adverse reaction began within an hour of exposure, starting
with burning of the eye. The problem quickly spread to the other eye, and then
my lips became numb about two hours into the ordeal. About this time, I
experienced the worst case of fidgets ever encountered. Shortness of breath
began after about four hours. With a quick visit to the emergency room and a
shot of antihistamine, recovery was almost instantaneous.
Mine was a classic case of anaphylactic shock, the same kind of problem
people allergic to peanuts, soy products or dairy products experience.
There is no doubt that plant poisonings do occur, but the incidence of
fatality is so low that it is not statistically different than that of being hit
by a meteor. However, a high percentage of the 2.3 million cases of human
exposure reported to the nation’s network of Poison Control Centers in 2000 were
The majority of these were cases of toddlers taking a bite out of a plant and
then a panicked parent making a dash for the nearest hospital. While some
ornamental plants are poisonous, the likelihood of a child ingesting a
sufficiently large dose to have an adverse reaction is remote.
My experience points out the difficulty of developing a completely accurate
and universally accepted list of poisonous plants. Most would never consider
peanuts to be poisonous. And to the majority of people, pencil cactus presents
no serious risk, but I now treat it with a great deal of respect. All plants are
a witches brew of organic compounds.
With small children it is always the best policy to keep plants out of the
way and to teach them at the earliest possible age to put only food in their
By: Gerald Klingaman, retired
Extension News -
February 1, 2002
The University of Arkansas Division of Agriculture does not maintain lists of retail outlets where these plants can be purchased. Please check your local nursery or other retail outlets to ask about the availability of these plants for your growing area.
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