Potentilla: Exposed Root by David Johnson See a large image of this tree Potentilla fruticosa is commonly known as potentilla or shrubby cinquefoil. It is not a tree but a shrub with exfoliating brown bark, bands of deadwood, dusty green foliage and yellow flowers (wild variety) from June to October. I collected this small shrub in September 1998. It was sandwiched between two pieces of rock that I was able to pry open so that I could remove the tree. What caught my attention was the thick trunk emerging from the rock. Often you see potentilla that are quite small with little trunk diameter. On opening up this rock sandwich, developed roots could be seen. At home, I potted the tree in a small training box and then waited for it to reemerge after winter. It took some time before the tree came out of dormancy and at first I thought it might be dead. During the summer of 1999 I let the tree recuperate and then in October I pruned and wired it. I had in mind a semi-cascade tree with the large lower right branch as the falling branch. However, there was an important flaw to this design concept. I had not really considered the exposed root style because I had read that this particular style was not as favoured as it had been in the past. I do not recall seeing any exposed root forms that I liked. Those I had seen seemed to be a mess of squiggly roots with a tree on top. They did not look consistent nor artistically appealing. But my biggest problem was being a slave to convention which narrowed my design options. In the spring of 2000, I tried to pot the tree in a cascade container but because of the long roots, I settled for a deep cascade pot with the hope that roots would develop higher up the tree. In the spring of 2001, I continued to follow my semi-cascade plan with determination. The tree had failed to get new roots higher up the tree while in the deep container so I repotted the tree in a shallow container. This time I wrapped the roots in sphagnum moss after applying rooting hormone still with the hope to develop roots higher up the tree so that I could get it into the "perfect" semi-cascade pot I had. In order to get the tree into this shallow pot, I had to prune the roots as much as I dared. The tree continued to put out lots of foliage just as it did the year before (2000). The flowers on potentilla appear later in the summer on the ends of that year's new growth. A decision has to be made that will influence the appearance of the tree: either incorporate long foliage extensions in your design or trim them off and loose the flowers. I have not come up with an answer to this paradox. Jerry Vlcek suggested that minimal fertilizing will get both tight growth and flowers but I have yet to try this, maybe next year. For my small shohin tree, I have chosen to cut back new growth. In the spring of 2002, again without many new roots higher up the tree, I finally did what the tree was trying to tell me to do all along. I chose to use the exposed root style that Mother Nature had spent all that time developing. Many bonsai professionals have long advocated listening to your trees. As before, I cut as many roots as I dared and then repotted the tree in a small blue Japanese container. The result was very small foliage throughout the tree. During the summer, another set of leaves emerged that were larger. These were pruned out to keep the foliage size small and consistent throughout the tree. Less fertilizer would have also helped. The large amount of exposed roots appeared to be a bit heavy in comparison to the delicate foliage above. So I began to remove bits of exfoliating bark from the exposed roots creating less mass and more air spaces. In this regard more work has to be done to reduce the exposed root mass. Next spring I may remove or reduce a root or two. Another task to do is to reduce the diameter of the falling first branch which is too thick compared to the main trunk. One interesting characteristic of potentilla is that the tree seems to grow with a combination of live veins twined together. This can make it easier to reduce a too heavy area by removing one or two of these veins. Care has to be taken by examining which vein is feeding which branches and removing those that can cause the least amount of damage. Another characteristic of potentilla related to its twisted vein growth is the poor healing over of large pruning cuts. A small cut on a growing vein will probably callus over but a large cut of an entire vein or large branch will probably die back without any callusing. I have found that when removing an entire vein or large branch, it is better to carefully rip it off creating a more natural dead wood area. But you have to be careful about this so that you don't rip off the living parts of the tree that you want to keep. Regarding the care and maintenance of potentilla, the Toronto Bonsai Society printed such an information sheet for the Bonsai Clubs International convention in Toronto 1997. It recommends repotting the tree in the spring in a well draining soil enriched with dolomite limestone. Potentilla need to have a moist root environment. This can be achieved by watering more frequently, planting the tree in a deeper pot or adding more organic material to the soil mixture. I have often come home after a hot or windy day to find the foliage drooping but after some misting and then some water they perk up. Potentilla are grown in full sun and are very winter hardy. The TBS sheet recommends fertilizing every two weeks with 20-20-20 and then a lower nitrogen amount (the first number) for an established tree in maintenance mode. The small leaves, flowers, collectability, winter hardiness, relatively quick development into a respectable bonsai, movement in the trunk, branches and deadwood, make potentilla a good candidate for your bonsai bench. ********************* For further reading, John Biel wrote an article on "Training Potentilla Bonsai" in International Bonsai 1997, number 2.