Japanese black pine is native to coastal Japan and South Korea and are common parkland trees in Japan. Because it is tolerant of poor, dry soil, pollution and salt it is sitable for planting in urban sites along streets. The shiny green needles, horizontal growth pattern, and charcoal-gray deeply fissured bark make it an attractive tree for bonsai. The best style for Japanese black pine are informal and formal upright but most styles can be employed except cascade. One of the best cultivars for bonsai is ‘Corticosa’ that has particularly thick, suberose bark.
Position: Plants should be grown outside in full sun with good air circulation. In winter the plants should be protected with temperatures go below 23F by putting them into an unheated area such as a garage.
Water: Provide water consistently so that the roots neither dry out nor are in saturated soil. Protect from prolonged rainfall, especially in winter. Make sure that soil drains well.
Fertilizer: Half strength fertilizer every two weeks; use balanced fertilizer from spring to summer and nitrogen free fertilizer in autumn. Twice a year provide chelated iron.
Repotting: Repot inn spring just before the buds begin to swell or in late summer; for young plants every two to three years, for older ones every three to five years. Look for a white fluffy substance among the roots. If it moves, it is aphids so get rid of it; if it does not move it is a beneficial mycorrhizal fungus so don’t disturb it. Be sure to leave a good root system.
Soil: Mixture of 40% soil, 10% peat, and 50% coarse sand.
Pruning: Shorten the shoots in early spring and eliminate the central buds of each branch in autumn. Needle reduction should be undertaken with the help of an expert.
Wiring: Wire in winter taking care to protect the bark (with raffia, for example). Be patient as wiring may take longer than with other plants.
Propagation: Seeds, layering, cuttings