Acer

Common name: Maple

Acer (aceraceae) of which there are many species, originate from North America,Europe and Asia.

Having said that, it is the species originating from China and Japan with their their decorative foliage and bark that are the type/s that tend to be grown in most peoples gardens.

Because of this attribute these are the type that will be discussed here on this website.

Acers are slow growing deciduous trees/shrubs, and most cultivars are fully winter hardy, however late spring frosts can cause severe damage to emerging foliage.

Species such as acer palmatum (Japanese Maple) can grow to a height of around 4.5 metres (15ft) and have a spread of around 2.5 metres (8ft) making them suitable for growing in relatively small gardens.

With regular pruning and care many of the shrub types can make good subjects for growing in containers.

This same attribute also makes them suitable subjects for Bonsai culture.

In the garden they appreciate free-draining and humus-rich soil that is slightly acidic and does not dry out in summer or become waterlogged in winter.

Most cultivars will adapt well to other soil types, but will not tolerate extremes of wet or dry and do not flourish in excessively alkaline soils.

Improve clay soil, by adding gravel/grit to help with winter drainage and organic matter to improve summer moisture retention.

The 'rubrum' species is tolerant of chalk, but does best in lime-free soil.

Asiatic species are lime-tolerant and require protection from cold winds, late frosts and early morning sun.

Variegated cultivars need partial shade to prevent sun scorch.

Red-leaved cultivars need some sun to develop their characteristic rich coloration.

Green-leaved cultivars will tolerate full sun but in hot conditions may scorch.

The most common problem leaf scorch, is when the foliage turns brown late in the season particularly around the margins and veins, then curl and shrivel.

This is caused by water being lost from the leaves faster than the roots can take it up.

It is not necessary to prune back unless the stems are damaged.

Such conditions do not usually kill plants, but those that show the symptoms should be well watered and sheltered even if this means erecting a temporary wind break.

Various factors can cause scorch, e.g. frost, drought, drying winds, hot sun and even salt-laden winds in coastal areas.

Maples are prone to attack by vine weevil, aphid and scale insects.

They are also prone to stem die-back.

Where this happens, prune the dead stems out to healthy wood.

Cultivation notes:

Week 12; Sow seed in a good seed compost and germinate at around 10°C (50°F) or alternatively place in a cold frame.

Expect germination to take around three weeks at 10°C (50°F) and much longer if using a cold frame.

Week 24; Prick out the seedlings into a nursery bed, when large enough to handle, and grow on for couple of years before planting out in permanent positions.

Alternatively; prick out into 70mm (3”) pots of potting compost and grow on in a cold frame.

Around Week 4 the following year and subsequent years, check to ensure the seedlings are not becoming ‘pot bound’

If they are, pot them up into the next sized pot and place back in the cold frame to grow on for another year or until such times as they are ready to go into their final quarters.

Plant out from Week 40 onwards (October-March) in cool, dappled shade sheltered from north and east winds.

A mulch of organic matter should be applied annually circa Week 10> to protect the shallow fibrous root systems from drying out.

Alternatively, a mulch of bark, clay pellets or grit can help to reduce water loss from the compost surface.

During hot weather plants may need watering twice a day to keep the compost moist

Feed with a balanced fertilizer from circa Week 15>

Pot culture

Acers / Japanese maples adapt well to pots if the compost is kept moist, use well drained loamy compost with added organic matter.

Feed with a liquid feed in spring and early summer and repot every two years if necessary.

Prior to planting, place broken clay pots or polystyrene in the base of the pot / container and fill with loam-based compost such as John Innes No. 2.

Plants will require re-potting every three to four years in spring before they start back into growth.

In winter, protect the container and roots from temperatures below -5 ° C (23° F) by covering the pot with bubble wrap or straw and raising it off the ground to aid drainage.

Most Acer species should be pruned in winter when dormant, they will 'bleed' badly if pruned in spring.

Prune to approx 25mm (1”) above a pair of buds, this will help to reduce the chance of ‘die back’, the spur formed will blacken to the buds and no further.

Young trees should be pruned to allow a central leader to form.

Once the leader has formed, keep pruning to a minimum, and just cut off sufficient to keep the desired shape.

To reduce height and / or width follow long branches back to a side branch and prune out at that point.

Prostrate trees should be allowed to spread naturally.

Snake bark maples should be pruned in late summer, pruning cuts heal much more quickly when they are in full growth.

Winter pruning may result in die-back caused by fungal spores to entering the slow healing wound.

Still on pruning: Many specimens purchased from garden centres are often the result of 'grafting' where the tip of a tender variety has been grafted on to a more vigorous root stock.

Although this is good for the general health and appearance of the plant one must remain vigilant that 'sucker' growths do not emanate from the root stock and swamp the growth from the grafted stock.

If this does occur prune the suckers right back to the source of their growth.





Top of the Page