Cryptomeria are of the Cupressacea family and are a monotypic genus where male and female strobili are borne on the same tree. The male strobili are orange to reddish and show in March and they form solitary round cones that mature within the first year. The common name is Japanese Cedar and they can be seen widely across Japan as impressive specimens of tree. Being a single species genus Cryptomeria japonica is the name which was previously known as Cryptomeria fortunei.
There are a few cultivars though worth merit and these include:-
- Araucarioides (Viminalis)
- Bandi-sugi – Small slow growing form and ideal for bonsai
- Compressa – Dwarf bush form, very slow growth, compact form
- Cristata – Fasciated form of growth, very unusual in form with cockscomb growths
- Elegans – Tall and bushy habit and vibrant bronze autumn colour
- Elegans Aurea – Slower growing and less bronze in autumn
- Elegans Compacta – Dense, slow growth with juvenile foliage
- Elegans Nana – Smaller and slower growing form, softer foliage
- Globosa – Small dense dome shaped bush
- Globoas Nana (Lobbii Nana) – Even smaller form but very dense foliage
- Jindai-Sugi – Dwarf dense bush form with flat top, bright green new foliage
- Knaptonensis (Nana Albospica) – Conical medium to large tree form
- Lycopodiodes (Viminalis)
- Midare-sugi – Small bush like Elegans
- Monstrosa – Medium size and cluster forming foliage
- Nana – Dwarf slow growing form, creamy new shoot tips
- Pygmaea – Irregular habit, slow growth rate, cluster growth
- Pyramidata – Concial bush or small tree
- Rasen-sugi- Vigorous and tightly curled leaves
- Sekkan-sugi- Small tree, pale creamy yellow young foliage
- Selaginoides (Viminalis)
- Spiralis- Large tree form
- Spiraliter Falcata – Pendant tips of shoots, large tree
- Vilmoriniana – Dwarf form, bush shape, crowded branchlets, dense
- Viminalis- Large irregular bush with whorls
- Yatsubusa – Great form for bonsai, small dwarf form
(Source: The Hillier Manual of Trees and Shrubs 2002)
This is a stunning tree when grown as the Japanese Cedar and has an awesome autumn colour as it turns a reddish brown bronze so do not be alarmed if this occurs to your bonsai, it is natural and some turn brighter bronze or red than others. They tend to have a natural conical form but some are more domed shaped crowns depending on the cultivar. Cryptomeria japonica ‘Yatsubusa’ is a very popular cultivar for bonsai as is Bandi-sugi.
They can be used in a range of bonsai styles including groups, formal and informal uprights, root over rock or clasped to a rock, and twin trunk. Pruning the foliage can be achieved through pinching but some have found this does not leave dead browning tips as opposed to pruning with scissors but if this is done back to the correct growth point it can be more effective than pinching. Feed them heavily during spring through summer as this will aid the growth and development especially with the slower growing cultivars and light feed during the autumn and allow to rest for a few months prior to starting feeding more heavily in spring again.
They are very thirsty trees so you will need a good regular watering regime throughout the year and misting with foliar feed works well. They like good light levels but should be protected from strong sunlight in the summer as they can dry out. They also have the more fleshy type of root so will need winter frost protection. Also protect from full sun post pruning and ensure the foliage is kept misted but not overly wet as this can lead to leaf problems like leaf blight and leaf spot. They can also get mites like red spider mite and scale so check the foliage regularly for any signs of browning or pest infestations to treat early.
When structure pruning (usually during the summer and not during winter) there is an opportunity on Japanese Cedar to create jins as opposed to full branch removal and this can create an effective aged look to the final image of the tree can can always be removed in full later to suit the image. It also prevents some branches over developing in thickness to create knuckles or reverse taper on the trunk as the main growth is between the intersections of branches. When wiring take care as branches can be easily broken and this is usually carried out between late spring and summer to allow time to set before the winter and with the use of raffia this can reduce the potential for branch cracks or breakages to occur.