Procumbens Juniper Basics
From Larry White's Presentation at the April 2015 Meeting
Juniperus procumbens is a low-growing shrubby juniper native to the southern Japan. Its status as a wild plant is disputed; some authorities treat it as endemic on high mountains on Kyūshū and a few other islands off southern Japan, while others consider it native to the coasts of southern Japan (north to Chiba Prefecture) and also the southern and western coasts of Korea. It is closely related to Juniperus chinensis, and is sometimes treated as a variety of it, as J. chinensis var. procumbens.
It is a prostrate plant, which usually grows between 20–30 cm (8-12 inches) tall, although sometimes as high as 50 cm (20 inches); while it does not get very tall it can get quite wide, 2–4 m (6-12 feet) across or more, with long prostrate branches. The branches tend to intertwine and form a dense mat. The leaves are arranged in decussate whorls of three; all the leaves are juvenile form, needle-like, 6–8 mm (<.25 inches ) long and 1-1.5 mm broad, with two white stomatal bands on the inner face. It is dioecious with separate male and female plants. The cones are berry-like, globose, 8–9 mm (.25 inches) in diameter, dark blackish-brown with a pale blue-white waxy bloom, and contain two or three seeds (rarely one); they are mature in about 18 months. The male cones are 3–4 mm long, and shed their pollen in early spring. It is dioecious, producing cones of only one sex on each plant.
Cultivation and Uses
Several cultivars have been selected, the most widely grown being 'Nana', a slow-growing procumbent plant. Others include 'Bonin Isles', a strong-growing mat-forming plant collected on the Bonin Islands, and 'Green Mound', which may just be a renaming of 'Nana'. A variegated plant sold under the name J. procumbens 'Variegata' is actually a cultivar of J. chinensis misnamed.
Styling Procumbens Juniper
When styling nursery or pre-bonsai stock, determine what to keep by understanding what should be removed, or cut off.
- Remove all dead branches (unless foreseen as jin branch)
- Remove all inactive or unhealthy foliage (no vigorous growth tip)
- Remove long and leggy branches
- Remove branches that are too large for their position in the design of the tree (can also be prepped to be jin branch)
- Remove bar branches
- Eliminate crotch growth (either remove the growth, or the branch that forms the “crotch”)
- Remove straight up and straight down growth (unless it’ll be wired in a different direction)
- Prior to wiring, remove all dead needles
- Last, but not least, if it “bugs” you….cut it off!
Clean Up on Existing Bonsai
- Thin out foliage pads when they become too dense
- Thin out or jin competing branches
- Prune back coarse branches to finer ones
- Create shari in branches and trunk
- Regularly inspect for insects and spray as required
- Repot in January. Use extreme car when repotting, removing only the outer inch of old soil and the mat of roots that were on the bottom of the pot. Never “bare root” when transplanting
- Study your tree to ensure it has a pleasant balance and harmony within the design
- Prune coarse branches back to finer, actively growing branches
- Thin out remaining foliage, removing crowded foliage and foliage growing in the wrong direction
- Remove all dead needles, the wire and position branch
- Leave wire on, up to a year. Inspect regularly to ensure wire is not “cutting in” to the branch. Remove any wire that becomes too tight
- After a year, remove all the wire and allow the tree to grow/li>
- As branches grow, they will also bud back. Allow this back budding to grow into branches that will be strong enough to wire
- Prune the original branch end back to the new back budding, thin out foliage as before and wire
- As primary, secondary, and tertiary become set, only the outermost branches will require wire
- As the tree matures, some of the branches that have been styled my need to be thinned out to create room for the remaining branches. Always consider jinning these branches prior to removing them. It’s always best to have wired branches that become jin. This way the dead jin branches will have the same character as the live ones
- Add shari to the trunk a little at a time to a sense of age
- Shari can also be added to the branches to get them to grow in more of a ribbon shape as opposed to a cylindrical shape. This will also help add a sense of age to the tree
- Junipers get scale. There are a couple of different kinds that attack junipers. The most common are dark gray / black. They attach themselves to the branch and look almost like part of the branch. Often ants will distribute scale. The other type of scale looks like a white dot. Both are treated by using a spray oil, such as Ultrafine.
- Junipers look good with lots of jins and shari. Often people will turn dead branches into jins. Instead, larry prefers to wire all the live branches and then decide later which ones to turn into jins. That way the jins will have similar shape to the live branches.