Green Mound Juniper Bonsai Care Guide
Junipers make perfect bonsai, especially for beginners, and Juniperus procumbens 'Nana' is no exception. This plant only grows to about eight inches tall in its natural setting, and is a close relative of Juniperus chinensis, another common bonsai cultivar. There is some debate as to the conifer shrub's origins. Most experts agree it is endemic to Japan, though some believe it comes from the mountainous island regions and others attribute it to being a native of coastal regions of southern Japan. Still others call it a native of China. It can also be found in Korea.
Green Mound is hardy, low-growing, and displays beautiful, dense, hunter to blue-green foliage that lends itself well to shaping. The bark is brown with a cracked, aged look that adds to its charm as a bonsai.
This evergreen is extremely hardy and can easily be an indoor or outdoor plant, even in winter, although it needs protection from temperatures below the upper 50s. The roots require insulation from frost. This plant prefers filtered sunlight and may need to be moved out of direct afternoon summer sun. During the winter it needs to be allowed a rest period in cool surroundings and should not be exposed to extreme temperatures or drying wind. Failure to nurture dormancy in junipers may result in health problems down the road.
Green Mound prefers to dry out to some extent between watering. Check the soil about an inch below the surface – the soil should be dry up to that point but no further. One way to water this juniper is to submerge it until the water reaches the base of the trunk and then allow it to drain over a rack. Your watering routine will be dependent on the humidity and temperature conditions in your specific locale, so monitor the plant over time to assess the time period it takes for the soil to get dry enough to warrant watering. This species can also benefit from the use of a humidity tray or misting.
Junipers like frequent feedings – every two weeks throughout the growing season, from spring to fall. If using a general chemical fertilizer, administer at half-strength, as a miniature plant does not need as strong as mixture as a full-size one. Alternatively you may use a liquid formula of fish emulsion or seaweed.
Green Mound tends to grow quite fast during the growing season and the tight foliage allows it to be shaped into almost any traditional bonsai form (except broom). Its low-growing pattern makes it exceptionally suitable for cascade styles. Perform major pruning in spring or autumn, removing branches that are growing in an undesirable direction (for example downward from the parent branch). Maintenance pruning may be done throughout the entire growing season. As with most conifers you will want to pinch rather than clip the foliage to prevent browning at the tips. Pinching new shoots in the desired areas will encourage foliage production.
Wiring a Green Mound Juniper can be tricky because the bark is rather stiff. This should be performed in fall or early winter to allow for the plant to become accustomed to the new shape during its dormancy and to minimize cutting in of the wire. Use the smallest possible gauge of wire for the branch's size and do not wrap too tightly. Wire should be left on for approximately six weeks. The bark of a juniper bonsai is well-suited to textural elements such as jin.
Seeds can take years to germinate so cuttings are typically the preferred method of propagation for the Green Mound bonsai. If using softwood cuttings in summer it's best to use a fungicide and provide misting and bottom heat. Hardwood cuttings can be taken in fall and winter without the need for mist or heat.
This bonsai species should be repotted every one to two years until it is about six years old, then you can decrease the frequency to every three to five years. Spring and autumn are preferable for repotting, and this is a good time to remove any wires as well. Prune no more than one third of the root ball and transplant into well-draining soil. Give the plant a thorough watering and then keep in the shade – away from wind – for a few weeks in order to encourage root growth.
Insects/Pests & Diseases:
Green Mound, like all junipers, is vulnerable to spider mites. During an infestation the tips of foliage may turn gray. While spider mites are not usually terribly destructive, they are an unpleasant annoyance and you can use a mild insecticide to eradicate them. Multiple applications may be necessary.
Fungal infections are indicated by discoloration of foliage in a black or lavender/gray color. Keeping the bonsai well-ventilated will help deter this issue. If the bonsai does require treatment, be sure to choose a fungicide that specifies junipers on the label.