Juniperus chinensis ‘Shimpaku’
Shimpaku Junipers, also known as Sargent's Juniper or Juniperus chinensis ‘sargentii’ are native to Japan, the Sahalin peninsula and Kurile Islands is one of the most beloved of bonsai enthusiasts. This slow growing species makes an elegant addition to anyone’s bonsai collection and is quite hardy making it a great choice for a beginner that desires an exclusively outdoor bonsai for their collection.
When young, the Shimpaku has needle-like foliage that is soft to the touch. As the tree matures the foliage takes on its characteristic scale-like appearance. This bonsai is a slow-growing conifer, and boasts a naturally irregular shape with beautiful dark blue green to green foliage that is present year round with bark that is a pale brown color which develops ridges, furrows and an attractive peeling as the tree matures. It is nice to see the bark to peel in thin strip. The Shimpaku Juniper is excellent for bonsai with its trunk and branches ability to wire and bend easily.
It is highly important to understand that this is exclusively an outdoor bonsai. Bringing it indoors for any reason other than to temporarily show it off for very short intervals will ensure its death. As a year round outdoor bonsai, regardless of its hardiness in its full form, protection must be provided for this tree and especially the roots during the winter. Depending on where you live, how cold it's going to get and what kind of snow cover you receive you might be able to leave it outside in a sheltered spot - maybe with a covering of leaves. In colder areas you will need to bury the roots and add some protective covering or even bring it into an unheated garage. In the summer, it will tolerate all but the driest and hottest areas
Grows best outdoors in full sun to semi-shade as Shimpaku Junipers love soaking up tons of sunshine.
Water as needed to maintain a lightly moist soil. This bonsai will like to dry out a little between watering, but take care not to let the soil dry out completely. Though it will tolerate drought, this condition should not be allowed for an extended period. Spray the foliage during the growing season to provide additional humidity. Though its water requirements are significantly less in winter, it is best to ensure that even during the winter you make sure that you provide water—
Lightly and infrequently, and just enough to avoid letting it dry out completely.
Fertilize just before and during growing season until autumn once a month with a slow acting organic fertilizer. Avoid fertilizing your Juniper in the hottest part of the growing season. If your tree is stressed, you can feed a half strength balance 20-20-20 fertilizer every other week.
Pruning / Training:
Pruning is typically done in spring and summer and it is important to remember that needles cut by scissors will turn brown and that hard pruning will stress your bonsai considerably. That being said, when new growth reaches about one inch in length you will want to pinch it back by half using your thumb and fingers by giving a slight tug. Repeat as necessary until mid-September; excessive pinching should be avoided as removal of more than 40% of the total foliage results in the production of immature, needle-like foliage that will need time to revert back to scale foliage. Removing all foliage on a branch risks the death of that branch. Wiring is best done in autumn or early winter because the branches will become used to the new shape while the Juniper is dormant over the winter. Watch the wire carefully for signs that the wire is cutting into the bark during the growing season. If this happens, be sure to remove the wire. While the tree is dormant you don't need to worry about the wire getting too tight and cutting into the bark. Wire can usually remain for up to a year, though you should check every three months for signs of damage.
Insects / Pests:
Spider mites and Bag worms are the most common pest of the Juniper. These are easily controlled with horticultural or Neem oil. Maintaining good airflow around open foliage prevents the majority of insect problems. Shimpaku are largely disease free other than rare die backs that can occur from blight during a particularly wet season.
Propagation for Junipers is achieved with heel or mallet cuttings. Heel cuttings are made from side shoots produced on stems two or more years old. To make the cuttings, pull the side shoots from the main stem. Pull directly away from the tip end of the main stem. This usually leaves a heel of older, main-stem tissue attached to the basal end of the side shoot. The heel cutting also can be cut from the main stem with a knife. Mallet cuttings, similar to heel cuttings, include a complete cross-section of the older, main stem at the base of the side shoot. Use a knife or a pair of small pruning shears to make this cut. Use the tip of a sharp knife to make a 1- to 2-inch vertical cut down each side of the base of the cutting. Stripping off the lower side branches of the cutting during its preparation also can be considered slight wounding. For more severe wounding on difficult-to-root types or larger-diameter cuttings, make several vertical cuts. Or remove a thin slice of bark down one or both sides of the base of the cutting. Expose the cambium (the layers of cells between the bark and the wood), but avoid cutting deeply into the wood. Place in a moist rooting medium that has good drainage and provide plenty of warmth and light.
Repotting a Juniper is best done in mid spring after two to three years of being in the same pot (up to 10 years old), and every 3-5 years for older trees. Shimpaku Juniper is tolerant of a wide variety of Potting soil but prefers a freely draining soil of moderate depth. Shallow containers should be avoided except for temporary display. You can prune the roots when you repot, but don't take more than 1/3 to 1/4 of the roots.
As an additional reminder to the caregiver of a Juniper, it is imperative to remember that this bonsai will not tolerate indoor conditions. Just as a Christmas tree dries out and drops its needles indoors, a Juniper cannot survive in the conditions that are present in an indoor environment. Keeping it healthy and alive requires that you showcase its beauty outside. Other than that, this bonsai is easy to care for and should give you years of delight.