Over the years, I have grown a wide variety of succulent plants, representing many genera and curious growth habits, but I have only grown a few of the so-
This month’s plant of the month, Bursera fagaroides is a fine example of a pachycaul plant; it produces a very thick, short trunk, topped with a few main branches which typically spread horizontally. The trunk and main branches are of a grey-
True to the common name of this species, (“Mexican Frankincense”) it is related to Frankincense tree (Boswellia sacra). True Frankincense is native to Yemen, Oman, and Somalia, and is adapted to conditions of both low rainfall and very high temperatures (which frequently soar to 120 degrees Fahrenheit and more in habitat). While the true Frankincense is difficult to maintain in cultivation, Mexican Frankincense is comparatively easy, tolerating a wide variety of growing conditions. Where it is happy, Mexican Frankincense is a fast grower, with each stem producing multiple branches, each of which may grow 12 inches or more in a season, and the trunk and main branches growing noticeably thicker with each year. One of my favorite traits of this plant is the rich aroma it produces when the plant is disturbed, or its leaves are crushed – it resinous scent is little short of intoxicating. Its dried sap has been employed in incense, and medicinally, to relieve congestion, and to strengthen the immune system (much like true Frankincense).
Mexican Frankincense is easy to grow, provided that you cater to a few of its specific needs. It grows best during the heart of summer when light is particularly intense, and temperatures are high. I have found that unless you have a greenhouse or a very sunny Florida room, it is best to grow this plant outdoors in the full sun from mid May through the summer months, to benefit from increased sunlight and warm temperatures. Even though this species will regularly experience temperatures above 100 degrees in habitat (it is native to the extreme southwestern corner of Arizona and south, well into central and western Mexico), our summer temperatures, averaging between the mid 70’s to the high 90’s appears to be warm enough for it to produce good growth. It is my impression that without this period of warm temperatures and bright light, this species will not thrive – it is not really suited for a year-
Mexican Frankincense will eventually become a large plant; even so, it can be kept compact with extensive annual pruning. I usually prune my plant in early spring, just as my plant is breaking dormancy. I am ruthless with my pruning, cutting back the previous year’s growth to about an inch or two. Not only will this keep the plant compact, but it also encourages branching, producing a less gangly looking plant. True aficionados will object that my plant does not have the typical growth habit of a plant in habitat, but I am trying some bonsai techniques, which I hope will eventually produce a plant with the general appearance of a miniature Baobab tree. Pruning releases copious amounts of milky sap, which emits a heady fragrance. Sometimes the sap will congeal into small globules of resin which may be harvested and added to incense or melted and added to candle wax to produce a distinctively scented candle. You may also try to root a few of the pruned cuttings to propagate additional plants. Many growers insist that this plant is easily grown from cuttings, but this has not been my experience – I have tried to root hardwood cuttings (taken in spring) and softwood cuttings from new summer growth, and neither time did I manage to get any to root. I am trying a different technique, called air layering, which attempts to produce rooted stems while the stems are still attached to the plant: a stem is nicked with a sharp knife or blade, and is treated with a rooting hormone, and is then wrapped with sphagnum or other rooting medium, and is then wrapped in polyethylene plastic to maintain high moisture. I expect that this will result in a good number of rooted cuttings in months to come – time will tell.
When temperatures drop to nearly freezing in fall, I finally bring my plant indoors to a very cool area: any cool, frost free area will do; breezeways, Florida rooms, a chilly alcove or a cool basement or attic (I keep mine in the basement, where temperatures may dip to the low 50’s in winter). The cooler temperatures should induce this plant to drop practically all of its leaves. By maintaining cooler temperatures, and keeping the soil dry throughout the winter months (giving only an occasional light watering to prevent root loss), this plant should remain dormant throughout the winter months. Monitor it throughout the winter – if the dormant buds appear to be too dry, you may need to increase the frequency of watering, but if it is breaking dormancy, and producing new leaves, it may need to be kept drier and a bit cooler to prevent it from growing at this time. If you can provide optimum growing conditions throughout the year, (if you can provide greenhouse conditions in the winter) then it is possible to grow this plant without a winter dormancy: growers in warmer parts of the country report that they can maintain year–round growth in their plants without ill-
Bursera fagaroides is distinctive for its smooth trunk and main stems; its attractive peeling bark gives this plant additional interest. It is one of the easiest and one of the most attractive members of the Bursera genus. In addition to its attractive appearance and distinctively swollen stems and branches, I especially like this plant for its fantastically scented resin. Not only is this a comparatively easy plant to find in the trade (a number of specialist nurseries carry plants of this species), but it is one of the easiest, and most forgiving species of the Frankincense family. This plant may not be for all growers–it can eventually grow to a fairly large size, and requires particularly bright light during the summer months for optimum growth, but with these concerns aside, there are few other plants that combine its distinctive appearance, relative ease of care, and its wonderfully scented sap. If you have never grown a pachycaul plant in the past, this would be an excellent plant to begin with.