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Black pines often used as bonsai and our club have had a
number of presentations about their care. The method of
training and caring for black pines also applies for most
other pines, so future articles on say white pine (aka five
needle pine) will rely on this article for the basics and
then discuss the differences.
If you discover an error in what we've written please let
us know.
Table of Contents
Initially we will address how to identify black pines,
how to fertilize and how to shorten new candles to produce
compact growth. In the future we will add more info such as
how to choose which new buds to keep and which to remove,
how to fertilize, etc.
Identifying Black Pines
Black pines have two needles in a sheath as
shown in figure 1.When grown as a landscape plant the
needles may be 4 inches long. On a bonsai we usually want
them to be 1 inch or less. New needles are bright green and
somewhat springy to the touch. During the summer the needles
will become harder and very sharp -- pressing your hand
against the needles can be painful.
Other pines with two needles per sheath include:
- Cork Bark Black Pines -- this variation has
very thick bark that looks like "wings" running up and
down the trunk. These pines are much weaker than regular
black pines and must be handled differently.
- Red Pines - needles are the same color as
black pines but are only 1/3-1/2 the thickness of a black
pine needle. The needles are also softer and more
flexible.
- Mugho or Swiss Mountain Pines - needles are the same color as
black pines but aren't as sharp or as long.
- Monterey Pines - needles are the same color as
black pines but are soft and springy all year round.
- Scotch Pines - needles are blue-green needles
and often have flaking orange bark.
For information about other kinds of Pines, see Sandy
Planting's June 2001 presentation
here.
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Figure 1 -- Black Pine
Needles
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When to Repot
Pines should be repotted during late April or
early May because you will create shorter needle growth.
How do you know that your pine needs to be repotted this
year? Younger trees grow faster than older trees so you may
need to repot every year or two initially, but only ever
three to five years after the tree is mature. Here's a
couple of easy ways to tell if it's time.
- Is the plant pushing itself up out of the pot?
- Are roots coming out the bottom drain holes?
- Is it difficult to push a chopstick into the top of
the soil?
Black pines use the conifer mix described in the
Soil Basics
page. We also recommend adding 1/2-1 tablespoon of Super Phosphate and
1-2 tablespoons bone meal to the soil when repotting. These spur root
growth.
Fertilizing Black Pines
Fertilizing is a topic of great discussion
among bonsai people. There are those who say fertilizer
cakes best, or Osmocote, fish emulsion, Miracid, etc. Each
has its advantages. The easiest for a beginner to use is
Osmocote 19-6-12 -- timed release fertilizer pellets. You
may also occasionally use Miracid at half strength.
We recommend fertilizing beginning in late-February or
early-March. After candles are removed (see next section)
additional fertilizer should be added.
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Pot Size
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How Much Osmocote
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Small (e.g. 4" diameter)
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2-3 teaspoons
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Medium (e.g. 12"diameter)
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2-4 tablespoons
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Large (> 12" diameter)
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4-8 tablespoons
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The Osmocote package says that it is good for about 6
months, but in reality it doesn't last more than a couple of
months when used on bonsai because we water so frequently.
So, you'll need to need to replenish it every couple of
months.
How to Produce Compact
Growth
Our goal is to keep the distance between
branches small and in scale to the tree and to shorten the
needles so the tree looks more in scale. There are two
methods to do this. The traditional three step technique of
shortening the candles is described in an earlier article on
our website. A new
technique being taught by Kathy Shaner yields the same
results but can be done in one step. We recommend using this
instead of the three step technique and will describe it
now.
New Technique
Because the candle becomes the new branch and we want the
length of branches to be short and compact, we need to make
the candles short. Initially the candles will be longer than
we want. But, if we remove the first candle and force a new
set to grow this new set will be shorter. In addition,
rather than just one single candle (branch) we will have
multiple buds from which to choose -- allowing us to produce
more branches and going in the direction we want.
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Cutting the candle will force new buds to form
at the base of the old candle.
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Pine trees grow more strongly at the top of the
tree, so those candles will always be longer than the
candles at the bottom of the tree. Candles on the tips of
the branches receive more sun than candles nearer to the
trunk so they will also grow more strongly. Our goal is to
have candles (and thus branches) that are nearly the same
length, and the following technique helps us achieve that.
When To Cut
The time to cut back is as soon as the candle is open and
needles on the candle are open and spread. In the
Palo Alto area this is typically in late-May or early-June.
See the figure below.
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Initial Growth
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Needles Grow Straight Up
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Fully Open
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Once the needles are open, you will have about 3 weeks to
complete your pruning. We will cut all the candles back at
the same time but the length of the stub being left will
vary according to the size of the candle and according to
its location on the tree.
Stubs that are different lengths die back at different
rates. Longer stubs will take longer to die back, and so
when new buds form at the base of the candle, they will
start growing (aka "pushing") several days later than on
shorter stubs. As a result, the new candles will be more
nearly the same size.
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On top branches, or candles that are on the ends
of the branch and receiving full sun, the stub
should be 1 to 1.5 times as long as the diameter of
the candle being cut.
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Candles located on branches in the middle of
the tree would be cut so that the stubs are
about the same as the diameter of the candle.
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On bottom branches, or candles that are
"inside" the tree (partially shaded) the stub
should be 1/2 as long as the diameter of the
candle being cut. (as on the right)
Of course candles that are already very small
(e.g. hidden inside the tree) shouldn't be cut
at all.
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Important Note
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Your scissors should be extra sharp for a
clean cut. Also, make sure that you make your
cuts perpendicular -- cutting a candle on
a slant means the dormant buds at the base will
get an uneven start.
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Choosing Buds for Future Branches
Two weeks after you've cut candles you should see new buds growing at the base of the candle.
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There may be several new buds, but because you want to develop 2 horizontal branches you'll remove all unneeded buds.
Which buds should you remove?
Because you want two branches that
are "opposite" each other, you might choose to keep the buds shown to
the right. But its a bit more complicated than that. |
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You will want the branches to be of equal strength.
So, the first step is to remove the strongest or largest buds. |
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Now you'll want to look at what's left.
If you have buds that are opposite each other and on a horizontal line,
you'll want to use those. You may need to twist the branch a bit with
wire to make this work -- however putting wire on now is often tricky.
Because you don't want to damage the new buds wait a few months.
Now, if there are buds on the "bottom" you'll remove those.
And, finally remove any "extra" buds. |
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Removing Old Growth
Generally sometime in October you will want to remove last year's needles so you get new buds that can grow into new
branches. Last year's needles will begin to turn yellow and won't look very good. Now's the time to clean up your tree.
The goal of pulling needles (also known as needle thinning)
is to cause latent buds which are located at the base of the needle to
develop. Not every sheeth contains a latent bud, but a few do. By
carefully removing the needle you make it more likely that the bud will
develop. It also opens the tree up so more sunlight gets inside --
which causes the buds to develop.
Because Cork Bark
black pines are more delicate and it is easier to damage the bud, so we
recommend cutting the needles off just above the sheath. Needles on white pines
should also be cut. You can do this for all pines, but most people
just pull the needles on black pines, red pines, etc. because it is
faster. To minimize damage it is important to pull one needle at a
time! This is easier if you use tweezers.
How Many To Pull?
Because pines grow more vigorously at the top of the plant,
and on the ends of the branches, we balance the growth by leaving
different numbers of needles on different parts of the tree. Here's a
good rule of thumb -- for very healthy trees.
- 10-12 needle pairs on the bottom of the tree
- 7-8 needle pairs in the middle of the tree
- 5-6 needle pairs at the top of the tree
For branches that are closer to the trunk (and so get less sunlight) leave an additional 2-3 pairs of needles.
In January take a
look at your plant again. You may want to remove a couple more pairs of
needles on branches that look like they are growing more rapidly than
the others.
-- end
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Black Pine
Basics
