“Chinese Scale Juniper”
|In this article I will try to explain the pruning and maintenance of scale foliaged Junipers such as Juniperus Chinensis ‘Sargentii’ and Juniperus Chinensis x Media ‘Blaauw’. These varieties are very popular for bonsai due to their excellent tight compact growth to create nice tight foliage pads, as well as being quite prolific in back budding once they are pruned correctly. The natural habit of these species grows in a columnar form with dominant ascending branches, so it produces good low sacrificial branches to make the trunk thicken. These sacrificial branches should be thinned out to varying heights on the trunk, because the trunk can get inverse tapered if to many branches emerge from one point.
When pruning this species it is important to cut back to a secondary side shoot, when reducing the growth extension. You should cut along the central section of the shoot with sharp scissors remembering NOT to sever across the green foliage, as this will cause browning.
This species can get very dense around the apex of the tree where it gets maximum sunlight, so for specimen bonsai you should thin out during the summer months around the crown to allow light to enter to the lower branches. You should do this by plucking between the shoots and thinning around their junctions. If this is not done this species will naturally thin itself more heavily, this is called June fall, which is the yellowing and dropping of old inner growth.
In Japan the Scale Juniper grows far faster than in this country, this is mainly due to Japan’s much high humidity, so I have found the biggest problem is transpiration (moisture loss from the foliage due to sunlight) through its foliage. Therefore I have found this species puts on more growth extensions in a shadier area, rather than full sun, so I would especially recommend this positioning if major styling has been done to the tree.
This tree can be wired throughout the year, it will obviously have more suppleness in the branches during active growth, therefore if you need to move large branches do so accordingly.
You should fertilise with a slow release feed such as the rapeseed cakes from full active growth April-May until September. You can apply quite liberally providing the tree is healthy, but be careful with soluble buffer feeds that are high in Potassium, which will cause berries to form making the tree to lose energy. If this does happen you should remove the berries immediately by simply rubbing them off.
This species has a woody root system, so it is very susceptible to root rot. It also hates salts that can come from unwashed grit, so you must always make sure the aggregate you use is for horticultural use or thoroughly washed before using it.
When watering you should monitor the soil to make sure it drains quickly, if not be careful during the winter period by protecting from rain and frost. This tree does like to be regularly watered but not to sit it, so the fine Akadama top dressing should indicate when the tree is coming up to watering.
There are two main pest problems on Scale Juniper: The first is Conifer Mite that is very similar to red spider mite, which has the same symptoms of patchy yellowing and fine cobwebs, this can be cured with most insecticides such as Provado systemic insecticide made by Bio. The second main pest problem is Juniper scale, which can also be treated with a systemic insecticide.
This tree is quite hardy outside in Britain providing the soil is warm and free draining; in an Akadama soil based mix. The only problem with the frost is that it taints the foliage colour grey, so it can take a longer time to put on growth extensions in the spring due to waiting for the old foliage to green-up.