Dave Prescott on Junipers
The Juniper family ranges from the scale-like leaves of the Chinese "Shimpaku" (Juniperus Sargentii) to those with needle leaves (Juniperus Rigida). There are many cultivars and those with scale-like foliage may exhibit both the soft adult scales and the spiky juvenile forms on the same tree. The "San José" Juniper generally exhibits the juvenile form. J.Davidii has feathery foliage, which is difficult to train, whilst the "Sabina" Juniper is difficult to compact. J.Pfizera falls in between adult and juvenile foliage but if left to its own devices will tend towards the adult form. "Blaauws" Juniper, with its blue-grey adult foliage is a cultivar. In David's opinion, trees with variegated foliage and those showing both adult and juvenile foliage are best avoided. Trees should display either all adult or all juvenile foliage.
Over-watering, over-wiring, over-feeding or frequent repotting cause junipers to grow juvenile leaves. After any styling (root or branch) the tree may revert to juvenile growth and take some time before the leaves change back to their adult form. Junipers like to be kept on the dry side in a free draining medium and potted less frequently than deciduous trees. He recommended five years between re-potting, pruning and wiring, when using a compost of 30% Akadama 30% Bark 30% Grit. If the tree is kept pot bound it will revert to adult foliage.
If 'fiddled with' trees change to juvenile form. In reply to a question from one of the members, David said that he uses small amounts of light rape seed meal, sprinkled over to soil continuously all the year round, as a fertiliser. He also mixes chopped Sphagnum Moss with the Akadama and Grit, and uses charcoal in the bottom of the pot to keep the compost sweet.
Variegated and feathery types quickly revert to juvenile foliage and need frequent pinching and reduced water to compact them. Junipers kept in full shade will have dark green foliage whilst those kept in full sun will lighten. Spraying with an iron feed (Miracid) and keeping the tree in semi-shade will also darken the leaves. Lime Sulphur, diluted between 30:1 to 80:1 with water, will help to maintain colour and kill pests.
Juniper roots are susceptible to attack by fungal diseases. When digging up Yamadori, or field grown Junipers, wrap the roots in moist Sphagnum Moss before re-planting. This moss has both anti-fungal and anti-bacterial properties.
The following members trees were selected by David, from the many on display, for discussion and demonstration, giving advice on styling and future care.
1 - David C's Chinese Juniper
2 - Jim C's San José juniper "Blue Alps" (needle foliage)
3 - Don J's Expansa Variegata (adult variegated foliage)
4 - Julie B's Juniperus Davidii (feathery foliage)
5 -Mick C's Chinese Juniper (adult foliage)
6 - Roger R's "Shimpaku" (adult foliage)
Now (October) and Spring were good times to remove all the old inner foliage, the ones without green tips, which would die anyway because of lack of light. Aim to end up with a "tuft" at the end of each branchlet. Wire the tips upwards as for a pine. Remove all the long extension growth on "Shimpaku" by cutting off the longer ones and pinching the tips of smaller ones. Spring pruning is best because the tree will be growing strongly, whereas in Autumn it is just ticking over.
Having removed the old inner foliage David then continued styling Tree 6 by removing all the foliage from the lowest downward branch. This reduced the tree's width and eliminated a forked branch. This bare branch was retained and subsequently "Jinned". The tree was already potted in pure Akadama, for free drainage, and David informed the members that junipers could even be grown in pure grit.
Then he started to wire the tree with copper wire, commenting that junipers take a long time to set their branches. He prefers to leave the wire on until it almost cuts into the bark. However, once the branch is set there is no further need to keep the wire on. It is best to cut the wire off the tree, as copper wire work-hardens when applied and becomes too stiff to unwind. David preferred copper wire because aluminium wire is more expensive and less springy. Copper wire can be wound at 45° or more open but aluminium wire needs to have slightly closer coils. Put on as little wire as possible to do the job. When required, one thicker wire is better than two thinner ones. To lower a branch in total it is better to use a guy-wire (fishing line) to pull the branch down instead of conventionally wiring it. If it is necessary to cross a wire then cross the thinner wire over the thicker one underneath the branch, so that it is hidden and less unsightly.
When asked what treatment to give the trunks he replied that Needle types require none and that others could be cleaned with water and a toothbrush. The water will soften the bark and the brush will remove the top layer to expose the red colour beneath. It is only a cosmetic treatment more suitable for a show.
Once the tree had been wired, the downward hanging leaves were cut out with scissors to produce a flat underside to the foliage pads. He commented that it would have been better to scissor trim them regularly throughout the summer. The wired branchlets were fanned out to produce pads with a flat bottom, domed top and upturned tips. After trimming and styling, the tree should be given some protection, especially from frost during the winter.
answer to a question, David said that the best time to repot was mid-April
to May in Manchester, but a fortnight earlier in the South. However, repotting
could be done at any time if the roots were wrapped in Sphagnum moss but
not in December, or when it was cold, unless protection was given.
Junipers require little watering between October and April. Allow the compost to partially dry between watering. "Maxicrop Green" will green up the foliage. Junipers can suffer from Scale Insect and Red Spider Mite (invisible). Insecticides to use are "Picket", "Provado" or "Bugfree". Systemic insecticides are OK for Junipers but NOT for Chinese Elms, which will cause leaf-drop.
Junipers have living veins and if stressed, or attacked or infected, it will protect itself by closing down a branch and internally callus to block further damage to the whole tree. Junipers are difficult to bud back.
asking the members whether there were any further questions, David then
individually commented on the remaining trees on display giving suggestions
for improvement. Trevor thanked David for a most interesting and informative
talk. We had all benefited from his experience. After the meeting David
had the unenviable task of driving back to Manchester.
Meeting. 11th December 2001
The challenge of showing your trees in their winter finery.
Copyright & copy; 2001, Surrey Heath Bonsai Society.