How to grow Japanese red pine bonsai? A detailed guide to the latest cultivation methods

The Japanese red pine, also known as Japanese red pine, gray-fruited red pine, short-leaved red pine, etc., is a tall tree of the genus Pinus in the family Pinaceae, with very high ornamental value. It is suitable for planting on both sides of gate entrances or alone beside paths and on lawns, and is often paired with red maple and laceleaf maple; the glossy leaves and jade-green branches set each other off beautifully. It is also an excellent tree for stump bonsai. Now let us take a look together at the cultivation methods for Japanese red pine bonsai!

Ecological habits of the Japanese red pine

The Japanese red pine is a deep-rooted, light-loving tree species with strong wind resistance. It grows in temperate coastal mountainous areas and plains with annual rainfall of over 800 mm. It is more cold-tolerant than Masson pine and can tolerate poor soil. It can grow on neutral or acidic soils (pH 5 to 6) formed from weathered granite, gneiss and sandstone in mountainous areas. It is not tolerant of saline-alkaline soil, and grows poorly on poorly aerated heavy clay loam.

Cultivated varieties of the Japanese red pine

1. Globe-crowned Japanese red pine: The trunk is short and small, and the branches cluster from the base, extending straight upward to form a spherical crown. The leaves are relatively short and dense, and it is often cultivated as bonsai for ornamental use.

2. Umbrella-shaped Japanese red pine: A clustered large shrub, up to 4 m tall, with most trunks clustering upward from the base to form an umbrella-shaped crown. It is cultivated in Nanjing, Suzhou, Shanghai, Hangzhou and other places in China. It is a beautiful ornamental tree with very vigorous growth.

Propagation methods of the Japanese red pine

1. Sowing: Collect seeds in October. Sun-dry the cones for several days, turning them frequently. When the cone scales split, the seeds come out on their own. After cleaning, store dry and sow in February to March by broadcasting or drilling. After sowing, cover with sifted yellow subsoil or burnt mud ash just to the point where the seeds are no longer visible, then cover with rice straw and keep the soil moist. Seedlings emerge in mid-April; remove the straw promptly. Before and after sowing, special attention must be paid to controlling damping-off and other pests and diseases. The following spring, they can be divided and planted out for afforestation.

2. Grafting: For grafting Japanese red pine, use black pine as the rootstock. Select thick 1-year-old branches as scions and use the side-grafting method from mid-to-late February to early March. After grafting, mound soil up to the top of the scion. In dry weather, spray a little water to prevent the scion from withering. After survival, gradually remove the branches and leaves of the rootstock. By mid-to-late October, all branches and leaves of the rootstock can be cut off, but some may also be retained until the following year to cut. Weeping Japanese red pine can use the high-grafting method, which grows fast and takes shape early, but 5 to 6-year-old rootstocks should be selected.

Cultivation methods of the Japanese red pine

1. Watering: The Japanese red pine likes dryness and dislikes waterlogging. Do not water excessively; water only when the soil is dry, and water thoroughly when you do. Properly controlling water during the growing season can make the branches and trunk thick and short and the needles short and small, enhancing ornamental value. During high summer temperatures, the foliage can be sprayed with water frequently, which benefits growth.

2. Fertilizing: The Japanese red pine tolerates poor soil and can grow normally even when the soil lacks fertilizer, and this also promotes a short trunk, dense branches and short leaves. However, during the growing season, properly applying 1 to 2 times of thin, fully decomposed cake fertilizer water is beneficial for healthy growth and increases resistance to pests and diseases. 

3. Pruning: To maintain its graceful and elegant tree shape, Japanese red pine bonsai needs proper pruning. During the growing season, pruning is mainly by bud pinching. From March to April each year, when the new buds have elongated but have not yet produced needles, about 1/2 of each terminal bud can be pinched off. For bonsai that do not need to grow more branches, all terminal buds can be pinched off. For branches that affect the beauty of the tree shape, prune during the dormant period. 

4. Repotting: Japanese red pine bonsai is generally repotted once every 3 to 5 years, preferably in February to March. When repotting, keep the original root ball intact and take it out, remove 1/2 of the old soil, cut off overly long roots as well as dead and rotten roots, and at the same time prune some unnecessary branches and leaves to maintain balance between the upper and lower parts of the root ball. If the original pot is not large enough, replace it with a slightly larger new pot. The planting method is the same as for initial potting.