(Editor's Note: This article was originally published on August 23, 2010. Your questions and comments are welcome, but please be aware that authors of previously published articles may not be able to promptly respond to new questions or comments.)
One of the weirder group plants you can grow are those I call the stick plants. These are actually Euphorbias, though the common name for several of them are Pencil Cacti. They are not cacti at all, however, but succulent spineless plants from various warmer parts of the globe. Though many are from South Africa, it is interesting that many are from diverse areas of the world, from northern Africa, to the Mediterranean, and some from South America, Central American and even the U.S. These plants are a excellent demonstration of convergent evolution, and adaption to environmental conditions with independent development of the "stick" (leafless and spineless) architecture. It should be noted there are some true cacti also with the common name pencil cactus (a few Cylindropuntia and an Echinocereus share this common name as well). I have grown several of these peculiar Euphorbias, though are dozens more I have no experience with. This article will be an introduction to some of the more common "stick plant" Euphorbias.
Cylindropuntia kleiniae (left photo shindagger) and Echinocereus waldeisii (right photo CactusJordi) have the common name of pencil cacti, but these are true cacti
I am not including spiny species, like the Euphorbia baioensis (left) or the myriad leafless, spineless medusoid species like Euphorbia inermis (right), in this article
This is a difficult group of plants to make a lot of generalities about, as they vary quite a bit in their ease of growth, cold hardiness, tolerance of wet soils and need for sunlight. However, the plants I am most familiar with are some of the hardiest and easiest of all the succulents to grow, not to mention some of the easiest of the genus Euphorbia.
All these plants have that well-known toxic sap, typical of all the Euphorbia species. But for some reason, most of these stick Euphorbias seem more apt than other Euphorbias to release their saps with minimal trauma. This makes pruning and moving these plants a greater hazard in some ways than I find with most of the Euphorbias. On the other hand, none of these have spines which are commonly found throughout the Euphorbia world. So if one can avoid the sap, there are few other dangers with these plants. Avoiding the sap is not so easy and it can sit innocuously on ones' skin for hours and later on accidentally get rubbed into the eyes or onto other sensitive mucous membranes, resulting in a lot of intense burning (and potential blindness). Eating sap is also, obviously, recommended against, though it is not as toxic as some toxic plant lists make it out to be (ingestion often results in vomiting and possibly other gastrointestinal upsets, but actual lethal ingestion incidences in either people or animals is quite rare).
Euphorbia leucodendron cut oozing saps (left) Euphorbia tiraculli cut and sap (right)
Even compared to most other species of Euphorbia I have in the yard, these dinky, pencil-diameter plants seem to crank out a lot more sap for their size (Euphorbia pseudocactus hybrid on right oozing relatively little sap for its size)
Euphorbia tirucalli (Pencil Cactus or Pencil Tree) This is the most commonly grown of all the Stick Euphorbias and for good reason. It is probably the easiest Euphorbia to root, and to grow, and to keep alive in hot and cold weather (though of course it has its limits). It is one of the fastest-growing of all the succulents. I had a one foot tall seedling grow into an over 100 pound behemoth in just a few years, though it was still only a shrub at that point. Euphorbia tirucalli is native to much of Africa. The plant basically consists of a stem or trunk and lots of branches that end in stiff, tubular pale green growth about as big around as a pencil- hence the common names. Though most of the year this plant is leafless, growing points are often tipped with a few small, lancelote leaves only really noticeable if one looks closely. Flowers are brief and occur mostly in late spring, but, at least here in southern California, occasionally in early autumn as well. These too are not too noticeable. The plant is grown strictly for its peculiar lack of foliage and ease of growth and maintenance. However, maintenance is really not all that easy once this plant attains some significant size. Without regular pruning, branches quickly outgrow the limb's ability to support them and large shrubs and trees are constantly dropping branches. Unfortunately these branches are very heavy and often damage other plants growing below. If not removed, these branches will often root and create another obnoxious shrub. Pruning these is not a simple task, either. Though the wood is fairly soft and easy to cut, the sap quickly gums up saws and clippers, and sap drips in large quantities all over the place. Avoiding contact with sap of this plant is very difficult, and just brushing up against it will often result in sap on clothing or skin. I have handled the sap of dozens of species of Euphorbia, but for some reason, this species seems to have particularly irritating sap.
Large tree in southern California (left) detail of 'branches' (right photo DaylilySLP)
my own Euphorbia tirucalli 'Sticks of Fire' (left) and after windy weather (right)... blowing over and losing limbs is a common problem with this species
Sticks of Fire form used in landscaping, for good contrast (left); unusually red (stressed) example of this plant for sale at a nursery (right)
flowers (left) and leaves (right) of this plant (Euphorbia tirucali) Sticks of Fire form. Leaves and flowers are usually only briefly visible seasonally.
Euphorbia leucadendron (Cat Tails Euphorbia) This species is becoming more widely available and sometimes can be picked up at garden outlet centers. For a Madagascan native, this plant is amazingly hardy and resilient, nearly equal to ease and durability as is Euphorbia tirucalli. This plant is a bit thicker and much slower to form a tree shape than Euphorbia tirucalli. I have yet to see one actually grow into a tree in Southern California, but seen several photos of fairly large trees growing in Africa and Madagascar. Here in California it usually forms a huge shrubby mass. This is a neater, more upright plant than Euphorbia tirucalli with few branches that grow laterally at all. This one often is leafy (though very tiny leaves at near the growing tips) and it also has some relatively large stoma or pores that give it a somewhat speckled appearance. Like Euphorbia tirucalli, this is an extremely easy Euphorbia to root, and cuttings seem to take no matter how quickly I shove them into the ground (no time needed for a "cure" as is the case with many succulents). I think part of this easy root and lack of rotting behavior when freshly cut ends are stuck into soil is due to the massive quantities of sap this plant pours out when it's cut. The sap quickly seals and protects the cut surface makng subsequent fungal growth less likely.
Euphorbia leucadendron growing in the Los Angeles Arboretum (left); flowering and fruiting (right)
showing some leaf formation, if briefly (left) Flowering Euphorbia leucadendron (right)
Close up of stems and fruiting bodies (left) Cuttings off my own plant (needs to be hacked back regularly)- right
Euphorbia antisyphillitica (Candelilla) This distantly related species is a North American native and though rarely referred to as a Pencil Cactus, is more pencil-like in diameter than either of the other two Euphorbias mentioned so far. This plant is also called the wax plant due to its thick coating of wax (called Candelilla wax, from which candles are often made, as well as waterproofing lotions, lipstick, facial creams, gum and floor polish etc.) Historically it has been used in the treatment of syphilis; hence the name. I find this a very easy plant to grow and it has moderate cold tolerance (at least compared to the above two species), down to the low 20F without any damage. It is a suckering species, not really a branching one, and only grows a few feet tall, forming a thick colony of pale blue-grey flexible pencil-like stems (no leaves on this one). Seasonally it is covered with attractive but tiny pink and white flowers. It is another non-fussy Euphorbia I find particularly difficult to over or under water. However, under conditions of extremely low water (or severe root binding), it tends to get floppy and grow less upright.
Euphorbia antisyphillitica (both photos Xenomorf)
flowers and fruits
My own plant in pot going nuts
Below are other species of 'Stick Euphorbias' that I have seen growing around southern California, and a few others have photographed in Arizona
Euphorbia aphylla (in flower on right) is another leafless species.... aphylla means no leaves. This is a shorter species only growing a few feet tall
flowers and fruits of Euphorbia aphylla
Euphorbia kamponii is another great "stick" Euphorbia from Madagascar, and one I have grown in my garden (but eventually let it rot... not quite as easy as the above species). Left is photo of plant in southern California, and right is large tree in Thailand next to Kampon Tansacha, who the species was named after
Euphorbia mauritanica, a South African native, growing in southern California (left) and flower of this plant (right)
Euphorbia schimperi is an Arabian 'Pencil Cactus' (left) here growing in southern California; flowers of Euphorbia schimperi (right)
Euphorbia onoclada in my yard- still a young plant, but hardy (so far)
Euphorbia gregaria, a South African species, at the Huntington Gardens
not really the classic Pencil Cactus, these dead looking Madagascan plants are Euphorbia platyclada (more like flattened sticks, than pencils) in southern California
two species photographed in Arizona (by Xenomorf): left is Euphorbia dregeana, a South African native and right is Euphorbia lomelii, a native to the Sonoran desert in Baja California.
Another Arizona-grown plant (by Xenomorf), Euphorbia rhombifolia, another South African species. It seems the incredibly hot, dry weather in Arizona agrees with nearly all of the Stick Euphorbias
two greenhouse plants in Huntington Gardens, California: left is Euphorbia arbuscula (Socotra native) and right is Euphorbia cryptospinosa
These two Euphorbias are somewhat caudex-forming and are very short, leafless species, and not really that pencil-like, but I include them here anyway. Left is Euphorbia gariepina and right Euphorbia lignosa
Euphorbia weberbaueri (left) native to Peru Euphorbia spinosa (right photo CactusJordi) from the Mediterranean regions