Tonights club night we were fortunate to have an evening dedicated to Maples (Acers) and a brilliant presentation by Mark Kerry providing some very informative tips and methods for getting the most out of your maples. It was then followed by a more detailed look at some of the Club members own maple bonsai with Mark offerings advice on their development.
Position
Can tolerate full sun if healthy but may prefer dappled shade in hot weather. May get leaf scorch in windy/ sunny conditions so ensure they are protected.
Soils
Good drainage mixture but still moisture retentive. The mix I use is pure Akadama or mix Akadama with kiryu 10%. Maples can be susceptible to root rot in poor draining soils or with over watering.
Repotting
Best time for repotting is in the spring as buds starting to swell. Root pruning more drastic if tree healthy. Consider washing root ball if poor soil or developing root plate. Promote fibrous roots and phase out larger structural roots.
Feeding
Best time for feeding is when Maples are actively growing Feb- July / Aug. Ease off feeding towards the end of summer and avoid late feeds as this promotes frost damage on the vulnerable new late growth. Use slow release fertiliser as a method of application.
Water
Water all year. Water well but do not let stand in water.
Winter care
Most Japanese maples are hardy down to -10oC. Trident maples not frost hardy as they have fleshy roots. Take care not to overwater in winter. Use cold green house protection if available. Remove dead leaves when fallen as these harbour pests & diseases. Protect new growth from frosts.
Wiring
Maples can be wired but their soft / smooth bark is easily damaged. Clip & grow method is preferable to wiring.
Pruning
Minor pruning can be done all year except in early spring when sap flow strongest (bleeding). Easier to prune structure when out of leaf. Major pruning best done in growth season when tree has time to seal wound. Seal your cuts with cut paste or putty. Maples can be partially or fully defoliated but only do this if they are healthy.
Annual maintenance
Spring – Repot Feb/March and then start to feed when tree growing unless repotted in spring, wait 6-8 weeks after repotting to start feeding.
Summer / Autumn – Pruning & feeding up until July/ August.
Winter – Stop feeding and water sparingly. Protect from frost if applicable.Â
Pruning for ramification
Why prune? You prune to develop shape, structure, promote back budding, keep smaller, get denser foliage, ramification, smaller leaves, more leaves, renew vigour.
Dominance – Apical or basal dominance need to know which species prefer which. Ie Trident maple are top apical dominance while Kiyohime are basal or side dominance growth so support weak inner growth by reducing stronger side growth as this will improve light levels into the canopy.
Ramification is dense twiggy growth and good taper on all branches that start thick then thinning down to tip with lots of buds along branches forming twigs.
Pruning
Letting new growth grow vigorously can result in in proportionally node length unless thickening branch. Generally cut to first or second pair. Once all branches cut, then thin out the leaves to let light into the canopy. Aim is to remove one of each pair or cut across leaves to reduce leaf area.
Creating a good quality winter silhouette for your tree will mean that at times of the year your tree will not look its best due to pruning but end image to aim for is winter image.Â
Pruning undesirable branches – to follow a style but can have more natural style too but things to look out for
- Suckers
- Branches bending or blocking views
- Limbs that grow too close to the ground
- Weak branches at bottom
- Downward dropping branches
- Dead branches not species for deadwood
- Crossing branches
- Branches returning to centre of tree
- Upward growing branches in centre of tree
- Bar branches
- Branches with unnatural twists and turns
- Parallel growing branches
- Branches extending beyond the tree line or canopy outline
- Branches growing from the same height of the trunk
- Branches that compete with the apex
- Disproportionately thick branches at top
Propagation
- Seeds
- Cuttings – hardwood and semi hardwood cutting material suitable
- Air layers – work well in late spring to start them
- Grafting for named varieties – Acer palmatum main root stock
More advanced techniques
- Improving the nebari – root system
- Root grafting
- Approach grafting
- Thread grafting
- Air layering
- Growing through a tile
- NB: If drilling, drill slowly as drilling creates heat and use clean sharp drill bits and clean up ends with sharp knife or scalpel. Need graft to make good contact and can use cocktail sticks.
Pest and diseases and disorders
- Vine weevil
- Vine weevil larvae
- Scale insects
- Aphids – black fly and green fly
- Mites
- Red spider mites
- Leaf gall
- Chlorosis
- Reversion
- Scorch
- Frost damage
- Use systemic insecticides like Provado and SB invigorator
Maple bonsai styles
- Raft
- Broom
- Group / Forest
- Twin trunk / Triple trunk
- Formal upright / Informal upright
- Clump
- Cascade / Semi cascade
- Root over rock / Exposed root
Maple pot selection
Tend to use muted colours like cream or off white. Strong colours detract from trees especially on larger trees. Use glazed pots, oval or soft rectangular pots as these work well with soft edges and inverted feet.
Maple varieties
Depending on the characteristics you are looking for maples come in all shapes, sizes and colours and offer seasonal variation across all seasons.
- Acer palmatum – Japanese maple – 5 lobed leaves
- Acer buergerianum– Trident maples – 3 lobed leaves
- Acer palmatum ‘Deshojo’ or Seigen – Red maples
- Acer palmatum ‘Arakawa’ – Rough barked maple
- Acer palmatum ‘Shisigashira’
- Acer palmatum ‘Kiyohime’
- Acer palmatum ‘Benichidori’
- Acer rubrum – Red maple
- Acer griseum – Paper bark maple
Books on maple
- Peter Adams – Bonsai with Japanese maples
- Andrea Meriggioli – Bonsai maples
- Gregory and Vertrees – Japanese maple guide
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