By Brian Gershuny

Continued from: ‘Growing Seedlings For Bonsai’.


Still year 1:
It is now fall and the maple seedlings have been in their 6" pots (or 1 gallon pots in some cases) for one growing season.  Up until now, the only goal was to develop the beginnings of a radial root system.  The top growth should look like any other seedling.  You are now preparing for the next growing phase which is developing a trunk.  You want an interesting shape and good taper.  There will be some variability in the amount of growth of the seedlings.  This is probably due to the severe root pruning you did initially.  There is no need to cull now.

Maples at this point should look like sticks that have just lost their leaves.  This is the best time to prune.  What you are looking for are the short internodes near the base of the tree.  You can prune anywhere from 6" down to 3" from the base. Be sure to put cut paste on the wound. You want to force many side branches.  They will thicken the trunk at the base. If there is an interesting branch that you want to develop into a trunk line, keep your cut and inch or two above it to allow for sap withdrawal.

Protect the seedlings for the winter by pushing all the pots together in a place that is sheltered from the wind.  Mulch the pots by pushing bark or leaves up against the outside of the exposed pots.

Year 2:
The second spring initiates the trunk development phase.  If the roots grew well the year before, there should be a lot of new buds on the remaining trunk.  Leave the pots mulched until late April (in NJ) to protect against late freezes and frost.  When you put the pots out into the growing area, space them about 11/2 ft apart, center to center.  Leave aisles so you are able to reach them later.

As you did last year, just let the tree grow.  Water and fertilize as you did last year.  You want long, unrefined growth.  This is to strengthen the roots and grow the lateral branches (which will not be part of the final Bonsai) that thicken the trunk.

In late June, go through your aisles and start looking for a trunk line.  Prune back about 1/4 inch from a node or small branch where you want to change direction of the trunk to add some interest.  Leave all the side branches.  This pruning also gives you a chance to view the health of your trees.  Cull out any trees that sick or are doing poorly.  Look at the roots to be sure there is no disease that might affect your other trees.

Now you need to make some decisions.  If you are going to grow the trees in the ground, which is the fastest way to develop the trunk, you will need to find a suitable site and prepare the soil.  Your other option is to continue to grow your trees in progressively larger pots.  Each has its advantages and disadvantages.  For smaller refined maples I prefer pots.  The cost is more and it is nearly impossible to get a very heavy trunk, but the quality of the tree and magnificent nebari makes up for it.  For the grand, heavy trunked specimen, only field grown will do.  Some of the refinement in the roots are sacrificed, but you can end up with a tree that makes people gasp.

If you are going to grow your maples in the field, you will need a sunny site.  Maples in the ground can take full sun.  Prepare the soil as you would any vegetable garden.  Rototill in organic matter or compost.  Add whatever amendments are needed to make a well drained soil.  Transplant in late August through early September.  Remove the tree from the pot disturbing the roots as little as possible.

Spread the roots out by forcing the root ball out from the center of the bottom.  Try not to knock the soil from the roots.  If there are any roots growing straight down from the center, cut them off. Seedlings that used the collar method should be ready to have the tap root cut off above the collar.

Dig a hole about 8"-12" deep and at least 1 foot wide.  Many growers place 1-11/2 square flat concrete pavers or exterior plywood barriers in the bottom of the hole to force the outward growth of the roots.  It works quite well.  I have used both with impressive results.  If you use a barrier, make sure there is no air under it.  Put 2-3 inches of soil on top of it.  Pile a cone of good soil on top of that or in the bottom of the hole (if not using a barrier).  Work the tree down on the cone to eliminate any air.  Fill in the rest of the soil so the tree is at the same level as it was in the pot.  Water well.

Prune the top to shape the trunk line, again.  Now prune out the weaker side branches and any branches on the inside of curves as to leave no more than 2-3 branches at each node.  Too many branches at one node will cause an ugly lump at that point.  Space the trees at least 3-4 feet apart as they can get quite large in this phase of development.  Do not mulch the trees now.  You want the sun’s warmth to promote root growth and weeds are not a problem at this time of year.  When winter arrives, lay a 2-4 inch thick layer of mulch or mowed leaves around each tree.

Field Grown - Year 3:
This year, just let everything grow.  Prune to form the trunk line 2 or 3 times, the last time just after the leaves fall.  Keep the soil moist, fertilized and free of weeds.  Be careful with weeding tools as the trees have a very shallow root system.  A weed preventer, such as Preen, is useful.  Keep any branches from growing on the inside of curves.  Mulch in the winter.

Year 4:
This is the second year growing in the ground.  Start it the same as last year, just let it grow.  In June, after the leaves are mature, begin pruning the thickest branches to the trunk. By this time you have a good idea of where the front will be.  Mark it with a large nail with a piece if ribbon in the ground. (not in the tree!)  prune off any branches in the front.  Don’t leave any stump. Be sure to use cut paste.  Sap withdrawal is not a problem this time of year.  Leave branches on the outside of curves and the back.  Prune off any branches growing on the inside of curves. Several new branches will sprout around the cut.  These will assist healing.  Thin them to  1 or 2 after a year when the cut has healed over.  Continue maintaining the trunk line.

In late August use a sharp very spade to cut down through the roots in the front of the tree at about a 45 degrees angle toward the center.  Cut about 16 inches from the trunk.  Finish the year by pruning the trunk line and mulch just as in previous years.

Year 5:
This year’s goal is to ready the tree for a training pot.  Like last year, wait for the leaves to mature, around June, and cut off the large branches.  At the same time root prune the left side just as you did in the front last year.  Follow this in one month by root pruning the right side.  In late August root prune the back.  Cut off any branches that will not be part of the final design.

Although you can leave the tree in the ground, pruning just the heaviest branches for a few years more, I do not think that the roots develop well.  If I plan to grow the trunk in the ground more, I give the tree a one year break in a training pot to correct and develop the roots.  In the early fall I will again plant the tree back into the ground.

If the trunks have developed sufficiently, they will go into training pots in spring.  I prefer wooden boxes.  I also like Kadon flats.  I build the wooden boxes during the winter.  The sides are made from 2x4s about 2’ square.  Bottoms are exterior plywood with holes drilled in it or 1" thick slats.  Leave about 1/4 - 1/2 between the slates for drainage and staple screening between them.  Be sure the flats are about 50% wider than any Bonsai pot that you would use for the final tree.  For larger trees, I use 2x6 boards for the sides.  Prepare soil as you did for the seedlings.

Year 6:
In spring, as the buds are just starting to swell, dig the maple from the ground.  Use a gentle spray of water to remove all of the field soil from roots to prevent root rot.  Be especially thorough directly underneath the trunk.  Prune and correct any problems with the roots now.  You will be planting the tree in the training pot just as you would transplant any Bonsai.  Wire the tree into the pot and use chopsticks to eliminate any air.  The training pot will correct and develop shallow roots and will develop refined branches.  It will be in this pot for 2 years.  At this point you only have a trunk.

By June of this year, you can begin selecting and wiring branches.  Avoid branches with long internodes by removing them or prune them back to the first acceptable node.  Wiring the thin branches now produces a good angle to the trunk and avoids branches that arch downward.  The branch will set in only a few weeks so keep a careful eye that the wire does not cut in.

Do not fertilize as heavy as in previous years.  Treat them as you would and other Bonsai.  The goal now is a refined branch system not rapid growth.  You want to avoid long internodes stimulated by heavy fertilizing.  If the roots have recovered well and growth is strong, you can defoliate the tree in June.  Do not defoliate after June or the tree will be too weak going into winter.  Be careful that the top does not get too heavy.  Thin the heaviest branches to keep a refined apex and good taper.

During the winter I put the boxes on the ground in an area sheltered from the wind and mulch up to the first branch.  Maples are very hardy.  In colder areas treat them as you would a hardy Bonsai.  Be sure not to let them dry out.

Year 7:
Continue developing the branches by letting the shoots grow out to 6-10 pairs of leaves and pruning back to 2-3 pairs.  Use sacrifice branches and wire to shape and balance the tree.  Do not over fertilize.  By the end of the year, when the leaves fall, you will have a good idea of what the final tree will look like and what kind of pot you want.

Year 8:
After two years in the training pot, the tree is ready for a Bonsai pot.  Like any maple Bonsai, the best time to transplant is in the spring when the buds begin to swell.  It will be a few more years until the tree is considered a work of art but you are well on your way.  Most trees will fit nicely in a pot 11/2 -2 inches deep.  Although it has been several years work (but not a lot of work) the results are magnificent and incomparable to any nursery tree you could find.

Grown In Pots Only - Year 3:
If your decision is to grow your seedlings in pots only, you will need to make some preparations.  First you will need the pots.  The next size after the 6" pots will be 3 gallon containers.  You want a pot wide enough for the roots to extend outward but still have enough depth to keep the roots from standing in water.  You can also avoid extra time transplanting and better simulate conditions in the ground by going right to a 5 gallon ‘squat’ pot.  If you are focusing on smaller bonsai stick to the 3 gallon pot.  Use  the same type of soil mix that you used with the seedlings adding 1 part more of sand.  Do not use garden soil as it drains poorly.

Transplant the seedlings in late August.  Spread the roots out from the bottom and plant the tree at the same level as it was growing in the 6" pot.  Minimize disturbing the soil around the roots.  Cut off any roots growing strait down from the center.  Cut off any wire collar if you used that method.

Prune the seedling just as if you had planted it in the ground.  Your goals at this point are the same.  You want to force lateral branches and develop an interesting trunk.  Let the lateral branches grow.  After  the leaves fall, do your final pruning.  Push the pots together and mulch around the outside.

Year 4 - pot
Each summer prune out the heaviest lateral branches keeping 2-3 at each node.  Continue forming the trunk line.  Check the roots each August to see if the tree will need to go into a larger pot.  When you need to transplant, spread and prune the roots as you did when you transplanted out of the 6" pots.  This time you will also trim the outer roots a few inches.  Cut back or off any extremely thick roots.  Correct any roots that are crossing or have other defects.  Use pins made out of wire as you would in a finished Bonsai.

Remember, as you develop the trunk, fertilize is important to promote heavy growth.  Try to stick to the ‘squat’ versions of pots to give the roots more lateral room to spread.  Protect the pots in winter with mulch.  Continue this process every year until you begin to get a trunk that is the size and shape that you want.  Keep heavy branches from growing on the inside of curves.

A few years later...
as the trunk approaches the size that you want, choose a front and mark it with a nail in the soil.  Keep branches from growing on that side to minimize scaring.  Be careful not to let the apex get to heavy,  at this point you will notice, if you are using both field growing and pot growing methods, that although your field trees are much thicker, the potted trees are much more refined with close internodes and exceptional nebari.

The tree will still need at least two years in the shallow training pot.  Because the root system has had more pruning over the years it is much finer.  You can transplant it into a box in early fall or spring.  I prefer spring in areas where the winters are more severe (zones 1-6).  The larger nursery pot affords more protection for the roots.  When you plan to transplant remove all the heavy thickening branches.  Some of the fine branches can be left on if you plan to develop them into final branches.  Wire them in the spring and develop then as described earlier in the article.

After two years you can transplant into a bonsai pot or you can develop the nebari even more by transplanting into shallower training pot.  I use a wooden box about 2" deep.  A very good article on this can be found in Bonsai Today #50.  When the tree finally makes it into a bonsai pot it will be a real showpiece.

I realize this is quite a lengthy article covering many years.  It takes many years to produce a truly great Bonsai tree.  There are no instant Bonsai.  The great Bonsai that you see in demonstrations or magazine article can only be made from great Pre-bonsai material.  I hope my experience will help you proudly show off a masterpiece and brag that you started it as a little twig.

Copyright 2000 Brian Gershuny.  All rights reserved.

2/00 B.G.