January 2009 General Meeting – Japanese Black Pine Overview

Posted by on Jan 8, 2009 in Articles And Stories

To kick off the Bonsai New Year, our own Eric Schrader gave a talk and demonstration on the “granddaddy of bonsai”, Japanese black pine.   Black pine is native to Korea, Japan and China and is widely considered the finest pine for bonsai as well as the “King of bonsai” (whatever that means…) Black pine care can seem complicated to the beginner and does take some time to understand, however once the basic concepts are in place the results that you will see from your black pines are fantastic.

The first thing to consider when looking at a pine that you own, or are considering purchasing, is the health of the tree.  Pines in general are slower to react to many environmental conditions than deciduous trees. They will take 2-3 years to become healthy if they are very sick but given poor conditions will continue to grow for 1-2 years before reacting adversely.   A popular test of the health of a Japanese Black Pine is to bounce the palm of your hand off the needles to see how sharp they are.  This technique in reality will tell you more about the variety than it will about the health of the tree.  Trees that are currently in distress from insect attacks may have very sharp needles since the needles are grown out the previous year.  Landscape variety trees tend to have longer needles, larger buds and sharper needles.  In contrast Mikawa and Arakawa varieties of black pine, both popular for bonsai, have finer growth patterns and softer needles.

To judge the health of the tree look at the following:

  • Length of the needles – sick trees will grow very slowly and may have short needles even without having been candle-cut the previous year.  If there is no sign that the tree was candle cut in the previous year but the needles are short the tree is not healthy.
  • Color and shine of the needles – A healthy tree will have  shiny dark green needles with no twisting, the needles will generally be stiff and strong.  If the needles are uniformly yellow this may indicate a temporary lack of nutrients or insect attack.  If the needles are yellow or brown on the tips or banded yellow this may indicate improper watering in the previous year and thus show that the tree has been stressed.
  • Interior buds – healthy trees will have small buds emerging on the branches closer to the trunk than the tips.  If there is no interior growth and the tree has long branches it is likely unhealthy and long-neglected.
  • Stong top growth – if the tree is exhibiting strong top growth (6-inch to foot-long straight sections or similar) it is likely healthy, but before purchasing consider whether or not the lower branches have enough buds to form good branching.

Generally, the more dense the foliage of a pine bonsai the longer it has been trained and cared for properly.  Given improper care the interior and lower branching will die first and then the tree will start to thin out.

Soil and Repotting

The first step in making a pine bonsai is to get the tree as healthy as possible.  Repot into a loose, well-draining bonsai mix made of 1 part pumice, 1 part akadama and 1 part lava.  All the components should be sifted to remove dust (they must be bone dry), and to make the sizes uniform.  If the sizes are not uniform that larger particles will tend toward the top of the pot effectively separating the components and making the soil conditions not uniform.  Use 1-16″ to 1/4″ size for JBP.   You should never completely bare-root a JBP, or any conifer really.  Instead, remove the tree from the pot, rake out and cut off the mass of roots on the bottom and flatten the bottom of the rootball.  Then set it on a table and comb out the matt of roots on the sides.  Leave the interior of the rootball intact unless this is the first time you have worked on the trees rootball.  If it is the first time bare root 1/4 to 1/2 of the rootball, less for very weak trees, more for healthier ones.  Go all the way to the trunk and replace the soil on the part of the rootball you intend to replace.  Do the other part on subsequent repottings, 1-2 years later.

Fertilization and Watering

Pines like heavy fertilization routines once repotted properly.  Fertilize more conservatively if you purchased the tree during the growing season and are unsure about the soil conditions.  For a 6″ pot add 2 cakes (tablespoon sized) or 2 tablespoons of organic fertilizer starting in March when the candles begin to elongate.  Add another 2 cakes or 2 tblsp or powder every two weeks until June 1st when the tree is decandled (if healthy and in San Francisco, more on that later).  If you run out of room on the surface of the pot remove the oldest cakes first.  Also, periodically use liquid chemical fertilizer such as miracle grow, diluted according to the package directions.  I use it once every week or two depending on when I have time.  For a 14″ pot you would double the number of cakes each time, so add 4 every two weeks.  If a crust of organic material forms on the surface of the soil scrape it off and  add fresh soil to restore air circulation to the roots.

Watering should be done so that the soil is damp but not wet when the tree is watered again.  If the tree stays too wet it will get root rot.  In my yard, I water trees in medium to large pots once a day typically, smaller pots twice a day on sunny days when warm.  Do not use a watering system, while they are convenient, they will not pay attention to when your tree is already too wet, they also promote moss growth and lichens which can damage the bark of a pine.

Sun and Wind

Black pines require full sun.  How many hours is that?….well, it is as many as you can give the tree.  Put your pines in the sunniest spot you have.  The sun is the source of food for the tree (fertilizer is really more like vitamins to a human.)  Black pines will never be healthy and will not respond well to training if they are in too much shade.

Avoid wind whenever possible, while it will not damage a pine as much as it damages tender-leafed plants, wind does nothing to help the tree.  Hot dry wind in warmer climates than San Francisco can kill a JBP.  They are a low land pine, like Monterey pines, and Japan is a humid place in the summer, unlike California.

Seasonal Care Cycle

Starting in November, on a healthy and vigorous tree,  remove all needles that are from previous years.  Remove enough of the new needles to make the tree roughly even throughout (e.g. remove some new needles from the top of the tree, but leave all the new needles on the bottom and interior.  Reduce budding from prior years decandling to 2, leaving either a smaller one on top and a larger one on the bottom or two equally sized buds side by side.  Select stronger interior buds along the branches to keep while removing the weaker ones  to even out strength of all buds.
Repot JBP in late January through the end of February.  Repotting in March or later will remove much of the new root growth and weaken the tree.  At this time remove more needles, reducing the tree (based on health, weaker trees should be left with more needles) to 7-8 pair on the top, 8-9 pair in middle areas, and 9-11 pair in weaker areas (bottom and interior.)

Fertilize heavily from the time candles start to move until June 1st. (see fertilization section above.)

On June 1st decandle trees.  This applies to the climate in San Francisco, CA.  If you live anywhere else, the date must be determined by trial and error….and even if you live in the city, there is variation.  For Bernal Heights I find that June 1st gives me good needle length for smaller to medium size trees.  On larger trees, or for slightly longer needles, decandle a week earlier.  As long as the tree is healthy it does not matter what the candle growth looks like when you cut it off, the important part of the operation is how long between the time the candles are cut and the end of the growing season.  The longer time there is the longer the needles will be.  The hotter and/or more humid it is the longer the needles will be.  Be sure to cut evenly across the base of the candle, do not cut at an angle and do not cut back further than about 1/16″ from the base of the candle.  If you do you will remove the dormant buds at the base that you want to sprout out.  When you decandle, remove all the fertilizer cakes from the surface of the pot and stop fertilizing with liquid for 4-6 weeks.  This will keep the needles shorter, more fertilizer or fertilizer sooner equals longer needles.

Do not decandle interior buds that are weak or just appeared the prior season – not decandling them will make them very strong, and the needles will be longer than the rest of the tree (scissor them to even out length, and more importantly – strength, in November.)
Bud thinning – I do not thin buds during the growing season, it only causes the remaining growth to become more vigorous, remove the excess buds in November when you clean up and wire the tree.
Starting around the first of August begin fertilizing more lightly than in the spring. Use half as many cakes as you did and apply liquid half as often until around the middle of October.

In November start the cycle again.

Basically all this information is based on the teaching of Boon Manakitivipart.