Along with Pines and Japanese Maples, Junipers are one of the three most frequently used genera for bonsai. Juniperus is a genus of 50+ species of evergreen, coniferous shrubs from dry forests and hillsides throughout the world.

Junipers have foliage of two types, needle-like juvenile foliage and scale-like adult foliage, species that exhibit predominantly one or the other are used for bonsai cultivation. The range of colour of the foliage ranges from steely-blue-greens to light greens occasionally with silver or gold hues.

Most of the classic Juniper bonsai in Japan have been collected as yamadori from the mountains and can reach ages of 200 years or more. Many display large amounts of natural and artificially created deadwood called jins and sharis which are bleached brilliant white with lime-sulphur.

Species and varieties suitable for bonsai

The classic Juniper for bonsai is often referred to as the Chinese Juniper. This is a naturally occurring hybrid species called Juniperus x media which is a cross between J.chinensis and J.sabina. (Confusingly Juniperus x media is also referred to in some textbooks as Juniperus pfitzeriana). The foliage can have a mixture of adult and juvenile foliage and as this combination can disrupt the design of a bonsai so varieties of J.media that display only one form of foliage tend to be used. Juniperus x media 'Blaauw' (named by a Dutch nursery 'Blaauw & co') is a strong growing conifer which carries bluish grey-green scale-like adult foliage. As with other J. x media, if needle-like juvenile foliage appears it can be pinched out until adult foliage appears.

Another very popular species for bonsai is Juniperus rigida, the 'Needle Juniper'. As the name suggests J. Rigida has sharply pointed needle foliage as has Juniperus communis a plant found growing wild in many parts of Europe, though it should be noted that collected J.communis is notoriously difficult to keep alive for more than 2 or 3 years after collection.

Juniperus squamata (needle foliage), J.sargentii (scale foliage), J.chinensis, J.Sabina, J.horizontalis procumbens, J.communis hornbrookii are also popularly used as can dozens of other species and varieties. What should be avoided however are the golden and variegated leaved varieties that are not best seen as bonsai.

Needle foliage of Juniperus rigida and Scale foliage of J. sargentii

Bonsai cultivation notes

Position Full sun though Junipers with predominately scale-like foliage benefit from a little shade from the midday sun. During winter protect during frosts below -10°C but coniferous trees should not be over wintered in dark outbuildings unless temperatures are consistently below -10°C, at this point there is no requirement for light.

Never try to grow Junipers indoors, though they may seem to tolerate indoor cultivation at first, poor humidity, lack of light and dormancy will eventually kill them. Do not trust a vendor, seller, book or website that claims Junipers can be grown successfully indoors! Dead Junipers can continue to display normal foliage colour for weeks or even months after they have effectively died.

Watering Ensure Junipers are not over watered as they suffer root rot easily, foliage should be misted frequently to help keep pores free of dust enabling them to breathe. In the case of trees that have been recently repotted or have root problems, misting is essential as conifers are able to absorb enough water through their leaf surface to maintain health until the roots are able to support the tree themselves. Misting also avoids excess transpiration and water loss on hot summer days.

Feeding Feed fortnightly; high nitrogen fertiliser from start of growth in Spring until mid-summer, balanced feed until late summer followed by low nitrogen until winter. Occasionally replacement feeds with an acidic fertiliser such as Miracid are highly recommended.

Repotting Every two years until around ten years of age then as necessary. A free-draining soil mix should be used. Repot in mid-spring as new growth appears though many Juniperus chinensis varieties can be repotted as late as July. Ensure that all grit or stone used in a soil mix is cleaned as alkaline deposits will adversely affect the tree. For Junipers suffering root rot; cut out all rooted roots and plant into pure sphagnum moss for a year. Sphagnum moss resists bacteria and decay and is very water absorbent. The moss will promote vigorous rootgrowth (at the expense of top-growth) in Junipers whilst its anti-bacterial properties halt the onset of further rotting of roots.

Pruning Junipers need continual pinching out to keep their foliage compact throughout the growing season. Do not use scissors, as this will cause the cut ends to brown. As with all conifers, branches should always be left with enough foliage to support them or they will die off. Try not to start pinching back until a month after visible growth first appears in late spring. Then foliage should be thinned out to reduce the volume of old inner growth that yellows and drops in June. Foliage pads should be pinched strongly around dominant growth areas. Pluck out juvenile growth to encourage scale-like adult growth. Wiring can be carried out at any time though the growing season is preferable. Trees wired during winter will require frost protection at temperatures below -5°C.

Propagation Root ripewood cuttings in Autumn, air-layering.

Pests and diseases Relatively disease free though scale can be a problem. Poor draining water retentive composts regularly cause root rot

Styling All forms except broom in all sizes.