Vaclav Novak Bonsai Pot Klika-Kuratkova. Saulieu 2017
Pinus is a genus of approximately 120 species of monoecious, evergreen, coniferous trees or shrubs, widely distributed throughout the world particularly occurring in mountainous and arid conditions where they are able to thrive.
Pines are a classic bonsai species in Japan and the world over, they are not however, easy trees to care for and style without experience. Pines have their own growth patterns that differ greatly from deciduous and common coniferous species; these growth patterns need to be understood before successful styling and pruning can be carried out.
As can be seen in the accompanying pictures; pines are not only used for bonsai in Japan, they are also very often seen cloud-pruned in Japanese gardens.
Pine foliage is in the form of needles that are most commonly formed in bundles of two’s and five’s. Some pine species have long and/or curved needles that make them difficult to style effectively as bonsai, however Pinus species that display short needles are nearly always suitable.
There are large numbers of pine species suitable for bonsai though for the purposes of this article I will outline the four most frequently used for bonsai;
PINUS MUGO/ MOUNTAIN PINE
The mountain pine originates from the mountain ranges of Central Europe. The species itself is very variable and botanists have sub-divided it into a series of sub-species and varieties.
Pinus mugo is very tough and is able to withstand the harshest of conditions. They have evolved to withstand extremely cold winter temperatures and hot, dry summer conditions. In favourable conditions, they will form dense bushy shrubs or small trees but given a poor situation they form scrubby, semi-prostrate twisted trees.
The main features that distinguish the mountain pine from the more familiar Scots pine (P. sylvestris) are the resinous buds and the shiny-green to purplish bark on young wood. P. mugo produce paired needles, 2-5cm long that are dark-green and slightly twisted. Cones start as violet-coloured flowers that grow in large numbers along new shoots.
PINUS THUNBERGII/ JAPANESE BLACK PINE
P. thunbergii is a native of Japan and is arguably the classic bonsai pine species. The Black Pine is a very vigorous tree commonly grown Japan in parks and ornamental gardens where heights of anything up to 25metres are commonly reached. Black Pines are very tolerant of poor conditions, surviving in nature on barren, stony soils. P. thunbergii has thick, dark grey-green needles up to 7-15cm long, though quite long, the needle-size can be reduced in length with the use of bonsai pruning techniques. Bark is purplish-grey and becomes very craggy and fissured with age.
Japanese Black Pines are relatively thirsty and can be watered fairly heavily compared to Japanese White Pines.
White pines are frequently grafted onto the more vigorous Black pine/ Pinus thunbergii rootstock to improve vigour and growth-rate.
PINUS SYLVESTRIS/ SCOTS PINE
Native to western and northern Europe, the Scots pine is a conical to columnar tree, which frequently loses its lower branches with maturity and takes a natural literati form. Needles are twisted, blue-green or yellow-green 5-7cm long and borne in pairs. Bark becomes flaky, red-brown with age.
Pinus sylvestris has given rise to a number of dwarf cultivars such as P.s. ‘Beuvronensis’ and P.s. ‘Waterii which are both excellent subjects for bonsai.
PINUS PARVIFLORA/ JAPANESE WHITE PINE
A conical or columnar tree, often with a spreading crown native to Japan. 2-6cm long leaves are a deep-green colour with whitish blue inner sides, giving rise to the name, the White Pine. White pines are frequently grafted onto the more vigorous Black pine/ Pinus thunbergii rootstock to improve vigour and growth-rate.
Japanese White Pine are naturally a mountain tree and require a fairly dry substrate. Indeed, this is one pine variety in particular that will suffer from overwatering and/or a water retentive soil.
BONSAI CULTIVATION NOTES
POSITION: Give pines as much sunlight as possible during Spring, Summer and Autumn. Insufficient sunlight will result in extended needle length and dieback of shaded branches. Though very hardy in Winter, Pines should be protected from freezing winds when their roots are frozen.
WATERING: All Pines dislike permanently wet soil though care should be taken to ensure their soil never dries out completely. It is important that a very fast-draining soil-medium is always used. Pines also benefit from regular misting.
It is often recommended that Pines are given minimal water during the Spring to reduce needle-length, as is discussed in an article on pruning pines elsewhere at Bonsai4me.com, my personal feeling is that the withdrawal of water is an unnecessary risk to the health of the tree.
FEEDING: The normal recommendation for feeding pines is to feed with a low-nitrogen fertiliser once in the Spring and then to withdraw all feed until new needles have hardened off in late-Summer. The idea being that by withdrawing fertiliser from the tree while the needles are extending, needle length will be reduced. The tree is then fed a high-nitrogen feed every 2-3 weeks until early-Autumn to encourage vigour and maximum back-budding.
PRUNING: When styling, be wary of reducing a nursery Pine’s top growth by more than 50% in one vegetative period. Reduce the height of the trunk (and foliage) slowly.
The general rule with mature (over 30-40 years) Pines is to keep to ‘only one insult per vegetative period’. After repotting, drastic pruning, wiring or styling you must then wait until 12 months elapses before carrying out any further work. This also means that if a Pine is styled in the Summer, it cannot be repotted the following Spring.
Immature, young pines will take more work than this each year without weakening but it must be remembered that Pines should always been developed slowly.
Trunk chopping and heavy branch pruning; carry out in Autumn when the sap flow in the tree is slower and sap loss will be reduced. Prune back the branch or trunk leaving a short stump. Seal the wound with Vaseline/petroleum jelly, this will seal the wound well, stop sap bleeding and not leave a hardened congealed mess at the wound-site. Allow the stump to dry out over the following year before either jinning it or removing the stump.
Repot in August-September (late Summer/early Autumn), this is a much better window of opportunity than the more traditionally advised timing of late Spring. Autumn repotting takes advantage of the huge increase in root production after the growing season, whereas spring repotting will disrupt growth during the year.
Once established in a good quality soil, repot infrequently every 3-5 years. Never bare-root a Juniper or change more than a third of the soil (or at very most half) in any one repotting.
Use a very free-draining soil-mix. When repotting, pine soils will often be seen to contain a white, thread-like fungus called Micorrhiza, which are very beneficial to the health of the tree.
When repotting, retain a small quantity of the old compost to ensure that Micorrhiza is retained in the new soil mix. For the same reason, do not wash the roots. Remove old, compacted soil by hand.
It is not necessary to prune any of the foliage of the pine after rootpruning to ‘balance’ the tree. The waxy needles of a Pine require relatively little moisture uptake from the roots and there is no need to try and reduce transpiration through the above-ground growth. The more foliage the tree has after root pruning, the more strength it will have to repair and regenerate the rootball. The tree will ‘balance’ the roots and foliage itself.
PROPAGATION: Sow seed of species outside in early Spring, the seed needs to be exposed to frosts to germinate. If the seed is fresh, germination can be rapid.
Cultivars need to be propagated by grafting in late Winter.
PESTS AND DISEASES: Aphids, sawfly larvae, and various needle cast diseases. Some 5-needle pines are susceptible to white pine needle rust.
Yellow needles; in early Autumn, Pines will discard old needles at this time of year and this can lead to a sudden colour change in the oldest needles on each shoot, they will fall away from the branches within a very short time.
General yellow needles across the tree in all Pines is indicative of a lack of air at the roots and frequently occurs when a Pine is planted in an old congealed soil that has collapsed. The solution is to slowly change the soil for a better draining, well-aerated substrate over the coming years.
Sudden needle discoloration and needle drop in Pines during Spring is indicative of Needle Cast, a fungal attack caused by fungi leaving on the branches of the tree. This is a difficult disease to cure and further advice should be sought.
STYLING: Suitable for all forms except broom.