I’m reposting this article that I originally wrote for the BSSF website about the arc of development of Japanese Black pine. Enjoy!
It’s likely that the confusion that sometimes surrounds black pine care is due to the different work needed during different phases of a tree’s life. Different care is also needed for trees that are growing slowly versus trees that are growing vigorously. Carefully examine your tree and try to determine how vigorous it is and what type of work is needed based on it’s age and shape.
Here is an outline of the basic care cycle detailed for Mature, semi-mature and young pines.
- Mature Trees
Starting in November– Thin the prior year growth to two buds at each decandling site and pull old needles from the tree. Some old needles can remain either to keep the tree full for show or to balance weaker branches with stronger ones. Aim to balance the entire tree by removing more needles from the stronger parts to reduce the vigor to match that of the weaker parts. Ignore tiny buds and very weak areas. You can either leave or remove small buds that are along the branches; consider if they are needed for further branch refinement or replacement of a leggy branch.
December through February – repot if needed, do not bare-root more than 50% of the rootball of a mature pine. Mature pines can go 3-5 years between repottings. If you live in a climate where frost or freezing temperatures occur protect repotted trees from colder temperatures until spring.
March-May – As the new candles begin to elongate you can twist off the top half of a few if they are much stronger than the rest of the candles. Hold the candle with one hand and twist off half the needles with the other. This is not decandling, this is another technique for equalizing growth. Fertilize heavily during spring growth to prepare for decandling in summer.
June-July – Decandle from June 1st through mid-July. The timing of decandling depends on heat, fertilizer routine and the health of the tree. Only healthy, vigorous trees should be decandled. In my yard in San Francisco I decandle starting on June 1st which is what I recommend for the eastern half of San Francisco. If you live in the western half decandle in the last week of May. Experiment with your conditions and adapt the date of decandling after assessing whether the needles were the correct length the previous year. If your needles were too short decandle earlier or use more fertilizer, if they are too long decandle later or reduce fertilizer after decandling. Decandle larger pines first and smaller ones later.
After the candles are removed thin old needles to control the relative vigor of the buds. Count the needle pairs left on each branch; leave more needles on lower and weaker branches and fewer needles on strong branches. 8-10 pair on strong areas, 10-12 on middle and 12-14 on weak areas.
- Semi-mature trees
Semi-mature trees are ones where the trunk is not being developed further but where branching is still sparse. The cycle is basically the same as above if the tree is healthy. Adjust decandling times to allow for slightly longer needles to maintain health of the tree. With trees that are weak do not pull old needles or decandle. A weak black pine can take 2 or 3 years to regain normal growth cycle, watch your tree carefully and do minimal work until the tree is healthy.
November – Assess strength – on strong trees prune long branches, thin shoots to two per terminal, select for equal strength, position and angle relative to the other bud. Consider design – if the branches need to be longer do not prune them. On weak trees thin only the strongest areas; leave all needles and buds in weaker areas.
December-February – Repotting is often the single-most important thing that will allow a pine to regain vigor and grow well. Do not bare-root an entire pine. If the tree is weak bare-root one-third or half of the rootball and feed heavily in the following season to get the tree healthy. One year later bare-root the other half or two-thirds of the tree to complete the repotting.
March-May – Fertilize, fertilize, fertilize. Use organic and chemical fertilizer. Do not remove new growth.
June-July – Consider decandling – on a weak tree decandling will be counter-productive. For strong trees follow the instructions above. Decandling of some branches, like the top half of the tree can radically shift the relative health of branches. If lower branches are weak and top branches are vigorous decandle selectively to try to re-balance the tree.
- Trees in development
With trees in development the challenge is to balance vigor between the sacrifice branch and the finished branches. Sacrifice branches are the only way to significantly increase the size and/or taper of the trunk. Consider using a well-placed branch on older and under-developed material to increase girth and taper. It is possible to maintain mature branching while simultaneously increasing trunk girth on black pine. 4-5 years of growth of a sacrifice branch done simultaneously with branch development can greatly increase the quality of many pines.
November – Wire young branches. Leave small buds on the trunk unwired unless they are the size of a chopstick and 4-5 inches in length. Reduce old needles only to maintain finished branches if they are dense. If branching is sparse leave old needles. If any branches were decandled perform the normal bud selection as with a mature tree on those branches.
Reduction of the sacrifice branch can be done at this time – anytime a sacrifice branch is reduced it will greatly increase the vigor of the lower branching. Cut up to 75% of the sacrifice branch off at one time but not all of it. Consider leaving the first side branch on the sacrifice as a new sacrifice.
December-February – 2-4 year old seedling pines can be completely bare-rooted. 1-3 years after the seedling cutting technique is used remove all soil and carefully spread the roots out to form the start of the nebari on the tree. Do not wire the roots or use wire to secure the tree in the pot. Use guy wires from the wire wrapped around the trunk to the container to secure the tree.
For pines growing in colanders (air-pruning the roots) in year 4-5 do not double-pot them as suggested in Bonsai Today #20 article. Slip the trees out of smaller containers and repot without root work into larger ones. This type of change can be done at any time during the year, not just during dormancy. Scrape topsoil that is clogged with organic fertilizer remnants off. Examine the surface roots for undesirable crossing roots and roots that wrap around the trunk, cut them off or gently reposition them. Refill the top with a thin layer of fresh soil. Significant root work on young pines that are growing vigorously will greatly reduce wood production on the trunk the following year, minimize root work to only correct drainage and improve the nebari.
March-May – Fertilize heavily. For trees in development more fertilizer will lead to faster growth and development. Remove female cones by gently twisting them off of the tips of the strong branches.
June-July – Consider the development of your tree. If the finished branches are weak or short do not decandle. Decandle to shorten nodes or selectively weaken branches. For small trees – shohin and kifu size – consider decandling behind the node to cause needle-buds which allow more compact growth. Sacrifice branches can be reduced at this time. Reduce no more than 75% of a large sacrifice. Removal of a strong sacrifice during this time can lead to excessive budding at the cut point which can cause reverse-taper. Plan ahead and reduce in stages.
September-October – Watch the development of the strong apical buds on 2-5 year old pines. On a strongly-growing young tree the terminal bud whorl will be too strong to keep as a part of the final design – there will be a bulge from the numerous buds. If you want to keep this part of the trunk as part of the design reduce the whorl to the central leading bud and one side bud. Use scissors to remove the buds.
- Pines from Seed
I find it quite enjoyable to develop black pine from seed in root air-pruning containers. Shohin trees can be grown from seed in 10 years with good branching, medium size trees will take 10-15 and larger trees will take 20 years or more. Many of my pines have a girth of 3 inches at age 8 with a basal root spread of 6-8 inches. With proper care the results are superior to nearly all nursery-grown material.
- Further Resources
Or, I highly recommend a few hours of reading on Bonsai Tonight which thoroughly covers many black-pine topics. Here are a few links:
Planting Pine Seeds
Seedling Cutting Technique
One Year Old Pine Seedlings
Wiring Three year old black pine
Repotting Young Pines
Repotting Young Pines part 2
Developing Young Pines
Thinning Japanese Black Pine
Pulling Needles on Black Pine
Pine Cutback basics