There are over 160 species in the genus Acer. However for bonsai purposes only 4 sections and their sub divisions are generally used for bonsai.
The majority of the maples (acers) that we are familiar with come originally from Japan, China and Korea, with the exception of Acer campestre (field maple), the origins of which come from Europe. The leaves of all varieties are deciduous and diacetate.
The leaves in most species are palmate, veined and lobed, with 3 to 9 (rarely to 13) veins each leading to a lobe, one of which is central or apical. The leaves resemble a hand with, in most cases, five pointed lobes – ‘Palma’ being the Latin for ‘palm of hand’.
The bark of younger trees is normally green or reddish-green and turns light grey or greyish-brown as it ages. The new shoots in spring can be yellow, orange or even bright red, and their red autumn foliage is very attractive.
They are extremely popular as bonsai and imported in vast numbers from Japan.
CULTIVARS - frequently used as bonsai
- Acer buergerianum (Trident maple)
- Acer palmatum ‘Shin-deshojo’
- Acer palmatum ‘Kiyohime’
- Acer palmatum ‘Seigen’
- Acer campestre (Field maple)
- Acer pseudoplatanus (sycamore)
GROWING AND CARE
- Maples prefer a sunny, airy position, but need some shade on very hot days. They are frost hardy, but should be protected from heavy frost and intense long-term freezing.
- Water maples regularly throughout the growing season. When they have dropped their leaves, this can be reduced to a bare minimum as they are not photosynthesising.
- Repot every one or two years, using a well-drained soil mixture. Prune the roots thoroughly – the pot will fill with roots quite quickly.
- Wire only when in leaf as twigs with less sap in them during winter are very prone to snapping.
- Shoots and twigs can be trimmed all year round.
- Regularly cut new growth back to one or two pairs of leaves on each twig. Prune strong branches only in autumn to prevent bleeding. Apply cut paste to the wounds as maples are prone to fungal infections.
- Similarly feeding should be fortnightly throughout the growing season.
- Maples are subject to aphid infestation, both greenfly and blackfly, so treat regularly with an insecticide.
- Poor autumn colour or purple-leaved varieties turning green may suggest a lack of light, such as being in a very shady spot
- Japanese maples can be very prone to leaf scorch in windy or excessively sunny positions, particularly those with fine-cut leaves. Young leaves can also be caught by frost so protect with horticultural fleece when cold nights are forecast.
SEASONAL CARE
- They need winter protection if you are not to lose fine twiggery.
- An unheated polytunnel is ideal, the trees go into the polytunnel in late November / December and are taken out in mid to late March or April.
- In the polytunnel the trees may freeze solid, but being protected from the winter wind and snow, risk of damage is low.
- Remember to water trees completely before putting them into winter protection and occasionally during the winter: damage can be done to a very dry tree.
PESTS AND DISEASES
- The leaves are used as a food plant for the larvae of a number of Lepidoptera caterpillars, like the green-striped maple-worm. They feed on the leaves so much that they cause temporary defoliation of host maple.
- Aphids are also very common sap-feeders on maples.
- Infestations of the long-horned beetle have resulted in the destruction of thousands of maples. Maples are affected by a number of fungal diseases.
- Several are susceptible to Verticillium wilt caused by Verticillium species, which can cause significant mortality.
- Sooty bark disease, caused by Cryptostroma species, can kill trees that are under stress due to drought.
- Death of maples can be caused by root rot and root decay.
- Maple leaves in late summer and autumn are commonly disfigured by "tar spot" and mildew, though these diseases do not usually have an adverse effect on the trees' long-term health.
- Choose your maple with care - avoid specimens with ugly pruning scars and groups of branches emerging from the same point. It looks unnatural and ugly and takes a lot of time and work to correct.
USEFUL TIPS FOR TRAINING AND CARING FOR MAPLE BONSAI
- Repot before new buds open; if a tree is repotted in cold weather do not let it freeze
- Wrap branch with raffia for heavy wire
- Prune major branches in winter
- Leaf prune healthy trees only during the month of June.
- Aluminium wire is best to use with maple as the branches are so brittle.
- Maples look well in shallow pots and especially in glazed pots.
- To develop good ramification, pinch out the centre of new growth after one set of leaves has opened.
- The objective to be achieved with maples is the finest terminal ramification possible. In order to achieve this, it is essential that pinching be done correctly. It is said that a maple bonsai starts with pinching and ends with pinching.
- Pinching maples must be done continually, every day on the growing benches. Maples are plants of rapid budding in spring and control of that growth is very important in order to avoid long internodes.
- Maples usually do not bud uniformly, but instead, some parts will do so before others, so that budding progress should be carefully noted with every watering.
- The secret of pinching is to balance the budding of the various parts of the tree. Shortly before they open, the tree itself will tell us which buds are the ones to pinch back first. These strong buds will be found on the upper parts of the tree and at the tips of the branches.
- The secret of pinching is to balance the budding of the various parts of the tree. Shortly before they open, the tree itself will tell us which buds are the ones to pinch back first. These strong buds will be found on the upper parts of the tree and at the tips of the branches.
- Many may be growing in places where they can be used to thicken parts of the trunk or to form a new branch, but others are undesirable
- Frequently many buds appear, all in a circle, in the intersections between trunk and branches on the high part of the tree. If they are left to grow, the apex would soon be as thick as the tree's base. Frequently many buds appear, all in a circle, in the intersections between trunk and branches on the high part of the tree. If they are left to grow, the apex would soon be as thick as the tree's base.