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The plant featured in this article is a rather an unusual species to be used for bonsai, Perovskia atriplicifolia or the 'Russian Sage' is a deciduous perennial more commonly seen growing in the garden flower-border.
I should say from the outset of this article that I would not recommend this species for bonsai; it is a fast-growing but relatively short-lived plant that suffers badly from dieback each Winter. However, with this tree I do think it is worth illustrating the short term pleasure that one can have with other similar fast-growing but short-lived and therefore 'unsuitable' species.
Despite its common name, P. atriplicifolia is native to Afghanistan. It is known as a 'sub-shrub'; a perennial shrub that is fully hardy but produces weak woody stems that frequently dieback to the ground during the Winter months (depending on the severity of the cold). As it is the below ground portions of the plant that are hardy, sub-shrubs have a strong tendency to produce many short-lived stems (or suckers) rather than one dominant trunk. Other common sub-shrubs include species such as lavender, thyme, heather and some fuchsias.
Sub-shrubs do have some useful characteristics; with an annual cycle that sees them growing many new stems('trunks') and branches and flowering prolifically all in the space of 4 or 5 months, sub-shrubs are very fast growing and very responsive to pruning during the growing season. They also have a tendency to have strong 'lifelines'. If a branch is removed, its entire sap-line back to (and including) the roots that supported the life growth, die back producing many interesting and natural shari.
Perovskia atriplicifolia itself produces grey-white shoots with deeply cut green-grey leaves and violet-blue flowers in tall panicles up to 12" tall in late Summer and early Autumn. Older wood develops a rough and flaking bark that creates a good impression of age after just a couple of years. One of Perovskia's best attributes is that if pruned or even slightly bruised, the leaves and the stems give off a pungent Lavender odour. As with most sub-shrubs, it is very fast growing.
In summary, sub-shrubs are not great for bonsai; while the base can live for a number of decades, any trunks that do form will rarely last more than 5-10 years and younger growth used for branching is very susceptible to dieback in Winter. Purposely developing such a species in the ground from a young nursery plant would be a very frustrating exercise; however, if the opportunity arises to use a large and interesting trunk dug up from the landscape, it doesn't hurt to try and create something a little unusual.
February 2006: this Perovskia had been growing in my garden for 7 or 8 years but was eventually removed to make room for other trees and shrubs.
Once dug up out of the ground, it seemed a pity to just throw or give away a plant with such a compact rootball and interesting trunks so I grabbed my camera, took a few pictures for posterity and decided to see if anything in the way of bonsai could be developed.
February 2006 continued: this tree was approached in the same way as with designing all bonsai. The trunk or trunkline(s) are paramount. The trunk(s) are at least mentally established before you even consider the branching. It is of no use to prune the raw material back so that it has great branching and a horrible trunk.
Great branching can be grown on a great trunk. A great trunk cannot (or can rarely) be developed without making a mess of great branching.
In my minds eye I could see that by turning the tree a little clockwise, I could produce a single or multi-trunked semi-cascade bonsai as can just be seen in the image above........
.........but not in this final 'potted up' image. For some reason I can only find an image of the back of this tree at this stage and not one of the front.
Prior to potting up the tree, the roots had been completely bare-rooted to remove all ground-soil before being planted into an inorganic soil mix. This is essential.