Maples

by Reiner Goebel

Maples – a rhapsody of colours and textures in spring and fall, majestic when in full foliage in summer, and even in winter, they delight us when they reveal their branch structure and twigginess. Not only does each plant offer continuous change, but the species has so many varieties with outstanding and differentiating characteristics, that one could easily build a collection containing nothing else, and yet still offer great variety.

I admit it: I am partial to maples. I have found them to be:

• easily adaptable to life in a pot
• vigorous and fast growing
• responsive to wiring and pruning techniques
• suitable for any style, with the possible exception of bunjin
• making respectable bonsai even with relatively young material
• reasonably hardy, and
• a little fickle when it comes to sun and wind

Most of the maples grown as bonsai are “Japanese maples”, which is a very loose term generally applied to varieties of Acer japonicum and Acer palmatum of which there are some 250. Many of these make excellent material for bonsai culture, and here is a short list:

ACER PALMATUM

• A. palmatum Kashima – dwarf form, rich green leaves, short internodes, hardy
• A. palmatum Kiyohime – small leaves, vigorous grower, gorgeous spring colour
• A. palmatum Kotohime – smallest leaves, twiggy growth habit, somewhat ‘ratty’ looking
• A. palmatum Okushimo – small green leaves on bright red petioles upright growth habit, golden colour in fall (frowned upon by bonsai purists because the leaf segments are curled but don’t listen to them – it’s a gorgeous plant)
• A. palmatum Seigen – bright crimson spring foliage, small leaves, multibranching
• A. palmatum Deshojo, Shindeshojo, Chishio, Chishio improved – bright red spring foliage
• A. palmatum Higasayama – spectacular spring buds, unattractive (in my view) variegated foliage that will “burn” off if exposed to full sun and make room for regular green palmatum leaves on second growth, very short internodes resulting in excellent twigginess

ACER JAPONICUM

• A. japonicum aureum – Golden Full Moon Maple- has yellow leaves that turn orange and red in the fall, very desirable specimen, slow growing, branch structure angular
• A. japonicum Junihitoye – smallest leaved of the japonicums, twiggy growth habit, brilliant orange fall colour

Other Maples

• A. buergerianum – Trident maple – one of the classic bonsai plants, shiny green leaves that reduce well under bonsai culture, noted for excellent surface roots in mature plants, good fall colour of orange and red, twiggy growth habit
• A. ginnala – Amur maple – leaves similar to Trident, not as shiny, excellent fall colour, readily available at local nurseries, h-a-r-d-y even in King City. If you don’t want to fuss a lot with winter sun and wind protection – this is the maple for you! The “ginnala” in the name translates into “Little mule”, and it sure is stubborn when it comes to surviving
• A. circinatum “Little Gem” – small leaves, green with a touch of red, orange and crimson in fall, short internodes

Styling

Although maples can be trained into many different styles, the most common styles are informal upright and broom, the styles normally adopted by their full-size brothers, and they look equally good as single trees or multiple tree groves. Their root system easily adapts to shallow pots and becomes quite fibrous after several years of bonsai culture.

Maples are ever ready to produce new buds on old wood. This tendency is of great help in the design of the tree. It may take some patience while the metamorphosis from bud to twig to branch takes place, but your patience will eventually be rewarded by a better design. The production of these so called adventitious buds is encouraged by pruning.

Pruning

Most maples are vigorous growers and lose their shape very quickly unless kept in check by a regular pruning routine. New shoots should be allowed to develop four or five mature sets of leaves before being cut back to one set. New growth will break from the buds in the axils of the last set of leaves remaining on the branch or twig. The new shoots will have shorter internodes, which is very desirable because it will ultimately result in a twiggier branch structure.

Maples, when pruned in fall or early spring, will bleed profusely from the wounds. This is more unsettling to the viewer than the tree. If you can’t bear the bleeding, wait with your pruning until May or June.

In the Toronto area, there will be two, maybe three, growth spurts that have to be pruned back in a growing season. The decision on how far a particular shoot should be cut back will also depend, of course, on how it fits into the shape desired for the plant. If a shoot develops in a spot where a branch is required, the shoot should be allowed to elongate until it reaches the dimension desired for the branch.

Occasionally, a maple will grow sucker sprouts. These are excessively vigorous shoots with internodes up to three times further apart than on the rest of the tree. Such sprouts should be pruned out as soon as they are recognized, because they only take away energy from regular growth and their coarseness rarely adds to the design.

Leaf Pruning

Leaf trimming or pruning is carried out on maples for three reasons:

1. to reduce leaf size,
2. to increase twigginess, and
3. to improve fall colour

Leaf pruning is carried out on healthy trees when the first crop of leaves has hardened off in late spring, which in Toronto will be some time towards the end of June. It is very important that the tree be vigorously growing at the time this procedure is carried out, because it puts great strain on the plant and may do it serious harm if it is not in the best of shape, horticulturally speaking. To give it the vigour it needs, it should be well fertilized during the preceding period.

The procedure itself consists of cutting off each leaf, leaving the petiole on the branch or twig until it (the petiole) falls off naturally after two to three weeks. The petiole will continue to nourish the tree for a while. The result of the procedure is that the tree will break out again not only at the axils (the point at which the old petioles were attached to the twigs), but also all along the trunk and branches.

The popping of buds all over the tree is quite spectacular, but should be curtailed to avoid unwanted growth. The buds that would result in undesirable branches should be rubbed off – before they open and elongate into branches – in order to avoid pruning scars.

After the leaves have all been cut off (which, incidentally, can be quite a job on a reasonably mature specimen), the tree should be exposed to full sun. The sunshine will encourage the growth of new leaves. Since the tree has lost its organs of evaporation, it should be protected from excessive moisture until the new crop of leaves is ready to fulfil its functions. If the soil is allowed to remain soggy during the defoliated stage there is a chance that the roots may suffer damage.

Although I find maples gorgeous all year round, I like them best in spring. And therein lies another bonus of leaf pruning: you get to experience the joys of spring twice – that in itself would be reason enough to practice this technique, even if it does seem like cheating on Mother Nature. Now – if I could only figure out a way to get two falls out of them!

Before I leave the subject of leaf pruning, I should mention that some varieties of Acer palmatum do not take kindly to this treatment. Maples belonging to a variety of A. palmatum dissectum (the ones with the deeply divided, lacy leaves) are not genetically vigorous enough to withstand the shock of losing all their leaves for no good reason, and may not break out again. Such a result would only be desirable if your favourite maple viewing season is winter: if you do not care for all that watering and fertilizing during the growing season, and if your aim is to produce kindling for the fireplace.

Wiring

Maples respond very well to wiring techniques. However, because of their generally vigorous growth habit, they have to be subjected to frequent close scrutiny to be able to take corrective measures before the wire cuts into the bark, which will be within three to four weeks during the active growing season – May, June, July. Damage caused by wire will be visible for years and should, therefore, be avoided at all costs, at least in those parts of the tree that are not hidden by the hopefully luxuriant foliage. But if you treasure the view of your tree in full frontal nudity, wire welts can be very distracting and it is worth avoiding them even in areas “normally” hidden by leaves.

Old branches are best wired in late winter (February and March) while they are bare. New shoots can be wired as they emerge and once they have elongated sufficiently. I try to wire new shoots somewhat loosely to give them some room to expand while the wood hardens and takes on the desired shape. If you merely wish to change the angle of a branch, the guy wire approach is good: the wire touches the branch in only one spot, which can be protected by a piece ot felt or rubber.

I cannot overemphasize the necessity of keeping a close watch on wired branches. No better way to prove that your maple is actually growing than to wire it in spring and forget about the wire until fall. Or summer! When I wired a maple for the first time and did not take a close look at it for about a month, I was more inclined to believe that the wire had shrunk in the rain than that the tree could have grown that much!

Another problem is that the bark of maples is very easily damaged in the process of applying the wire. Books recommend that you paper-wrap the wire to be used on maples. I had never seen such a papered wiring job until Chase Rosade’s workshop last month, when John B. wrapped his wire in green florist’s tape. It seemed simple enough. Another solution might be to use wire within its plastic coating – although the plastic coating precludes the wire from being annealed.

The plastic might also offend the bonsai purists, especially if it is pink or purple Since the wire is going to be on the tree for a short while only anyway, you can probably arrange it that no one else will see the tree during its period of degradation. Should another bonsai enthusiast drop by unannounced after all, you can always explain the misdemeanour as a horticultural experiment. This explanation gains in credibility if you use wire with at least five different colours of plastic on the same tree. If you photograph your trees in their various stages, don’t use colour film for a maple wired thusly.

Potting

Maples should be potted or repotted in early spring when the buds have swollen and are about to break out. They are not fussy as to soil, and I use my standard mixture of equal parts of humus, sand and haydite, adding an extra bit of humus. The root ball must be tied to the pot to stabilize the tree. Unless tied to the pot, the tree is likely to be uprooted in the first spring storm to come along.

Maples look best in shallow pots, either glazed or unglazed; if glazed, the colours of the glaze should harmonize with the foliage of the tree. Generally, blue, green, brown or cream glazes look good.

Since maples are vigorous growers, even mature trees will require repotting every two years, and young trees should be repotted annually.

Placement

All of the maples mentioned, with the exception of Trident and Amur maples, do not tolerate exposure to full sun without leaf burn. It is therefore recommended to place them in a position where they are protected from the afternoon sun. They are also susceptible to damage from wind, and their positioning should therefore be such that they are protected against excessive air movements.

While Tridents can withstand full sun without leaf burn, they will nevertheless not achieve their natural deep green leaf colouration unless they receive some shade in the afternoon. In all day full sun exposure, the leaves tend to be on the yellow side. In winter, it is prudent to provide Japanese maples with some sort of protection against the elements. All of the maples mentioned should survive in cold frames. I have personally wintered Full Moon, Trident and Kiyohime in window wells without problem. Higasayama survived dug in outside, although that was in a relatively mild winter. I wintered in a garage, they tend to jump the gun during a mild spell in January.

Fertilizing

Maples should be fertilized regularly during the growing season like all other bonsai. Only after potting should there be a three or four week period during which they are not fertilized.

Sources For Plants

Having read this treatise up to here, I bet you are chomping at the bit to find out where you can lay your hands on one of these beauties. Well, it ain’t so easy! Unless you decide to go for Amur maples or one of the relatively nondescript “Japanese maples” (mostly Bloodgood and Atropurpureum), which are in plentiful supply at local nurseries. If you don’t mind 3 or 7 hours worth of the most boring driving in North America and the chance of a hassle at the border, go visit Bill Valavanis’ International Bonsai Arboretum in Rochester. He has the most extensive selection of maples for bonsai (as well as anything else you might need) in reasonable reach of Toronto. Don’t go unannounced, though – phone -1-585-334-2595 for directions (or visit http://www.internationalbonsai.com on the Internet) and to make sure the place will be open when you get there. It’s definitely worth a visit, even if you only look. If you want to bring back plants, you must have an import permit, which Agriculture Canada will issue on application, and a phytosanitary certificate.

Reading Material

I have found the following books contain excellent information on maples as bonsai:

• “Japanese Maples” by J. D. Vertrees – a must for everyone interested in maples. Beautifully illustrated, with detailed descriptions of foliage colouration in spring and tall, growth habit, horticultural requirements, hardiness, etc..
• “The Art of Bonsai” by Peter D. Adams – good illustrations of pruning and wiring techniques, well illustrated throughout
• “The Japanese Art of Miniature Trees and Landscapes” by Yuji Yoshimura and Giovanna M. Halford – most noted for an outstanding short summary of bonsai data for 340 plants commonly grown as bonsai, giving their Japanese, English as well as Latin names.