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Tree of the Month - February 2005: Shimpaku Juniper
Juniperus sargentii, Shimpaku, Sargent Juniper, Chinese Juniper.
This plant used to be considered a subspecies as Juniperus chinensis var. sargentii and may still be described as this in some old books. Shimpaku has softer foliage than most other junipers, having the compressed scale foliage of the mature specimen even as a young plant. Adult leaves are diamond shaped and arranged in four ranks overlapping flat on the twigs like fish scales. It is considerably softer than the Chinese juniper, creating a more feathery appearance with the rounded scales instead of the immature foliage on the Chinese juniper. The bark is brown and shreds off in thin strips. Male and female cones are carried on separate plants. The female cones are fleshy, violet brown and berrylike, about a 0.5 in (1.3 cm) in diameter. Care is similar to other juniper bonsai but some points are always in order for a care reminder.
Shimpaku is climate tolerant from zones 3 to 9. This covers most of North America so it is one of the juniper bonsai first imagined by the general public. They need to go dormant for some period during the winter and it is better to leave them outside most of the year except for brief periods of indoor display.
Shimpaku grow best in full sun to partial-shade. More than a half day of shade will cause the growth to be leggy and thin. The plant can have a rather full ramification in the branch structure so this thin leggy growth will stand out poorly next to a healthy specimen. If grown in partial shade, morning sun is preferred to afternoon sun.
Junipers will tolerate and benefit from drying out slightly between waterings. I usually handle this by using a slightly coarser mix or not having as much organic material in the mix as for the other plants in my collection. Sieving out fine soil particles is particularly important for plants that like to dry out a little. Junipers will tolerate high humidity and misting in hot weather may help maintain health. Remember, misting is never a subsitute for watering.
Any balanced liquid fertilizer will work. Feed at half to 1/4 the normal strength once or twice monthly when new growth begins in Spring. Continue feeding on a monthly basis until the beginning of October. Alternatively, organic fertilizer balls can also be used. Junipers prefer an alkaline soil so small amounts of agricultural lime can be added to this as a supplement.
Repotting : Repotting is best done in early Spring after two years of being in the same pot for yung plants less than 6 years old. Older plants can go 4 to 6 years between repotting. If the spring window for repotting is missed then early fall is the next best time. As with any bonsai, age is relevant to the time spent in that general size pot. When radically changing pot size or shape, repot as if it were a young plant for at least one repotting cycle. Remove the plant (and fibrous rootball) from the container. Trim the rootball with a sharp pair of old scissors, removing approximately 1/4-1/2 inch of matted rootball from sides and bottom. At this point you can rake out the rest of the rootball gently if you wish. Replant into new or same pot using a well drained soil mix. Place newly planted plant in a shaded area for approximately 3-4 weeks and water regularly. After one month start feeding with liquid food. Pruning is typically done in spring and summer. When new growth reaches about one inch in length pinch back by using thumb and fingers and plucking gently. Repeat as necessary until mid-September. This improve the foliage pads greatly. ~ ZAC