Making the most of maples
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Because maples — the members of the genus Acer — are deciduous trees, with just a
few exceptions among the 150-odd species, many gardeners will instantly write
them off as being boring or dull. All those lifeless bare
branches in the winter. Well, that couldn’t be further from the truth;
maples are trees for all seasons. That doesn’t mean that all maples are
interesting all year, no, but a good selection is sure to provide year-round
interest.
Although maples are found over much of the temperate
northern hemisphere south of 59°N and at higher altitudes in the tropics, most
of the more commonly grown ornamental species, with their descendant varieties
and cultivars, are natives of temperate eastern Asia or North America. With the
exception of the Norway maple (A.
platanoides), which occurs in a huge range of foliage forms, the Eurasian
species tend to be relatively plain trees. The best known of these is
undoubtedly the sycamore maple (A.
pseudoplatanus), which, although encompassing a range of attractive
cultivars is perhaps best known for the myriad of winged seeds it produces in
the autumn. Still, I’m sure we all have childhood memories of playing with
sycamores, so it too has a place in gardens, albeit large gardens only.
Of course, many Growing
Today readers will know A.
pseudoplatanus as a timber tree, the wood of which is primarily used
musical instruments, especially violins, and for kitchen utensils as it doesn’t
affect the taste of food. The most beautifully grained examples are known as
curly or fiddleback and birdseye maple. Acer macrophyllum, A. rubrum and A. saccharinum also provide timber. The
maple most often used for construction, gymnasium floors,
bowling alleys and furniture is hard maple (A.
saccharum), which is very well known to we sweet-toothed non-timber
enthusiasts as the sugar maple, the main source of natural maple syrup. Its
leaf is the national emblem of Canada,
though the species is not exclusive to Canada
and is found over much of northern and eastern North America.
Now then, it’s time get down to specifics. What are the
various features of maples and which trees display the best of which features?
I’ll deal with features first and then detail a few of the more widely
available maples.
Top of the list is foliage. Indeed, if maples had nothing
else to recommend them they’d still be well worth growing for their foliage
alone. Some, especially the cultivars of Japanese maple (A. palmatum) and full moon maple (A. japonicum), have beautifully shaped
and finely divided foliage. Others, such as the Norway maple cultivars,
are known for their striking variegations and vivid colours; and virtually all
are renown for their striking autumn tones, which, at
their best, are among the most intense seen anywhere in nature. Of course,
getting good autumn colours depends greatly on the climate and the shades vary
from year to year even in districts known for their autumn foliage.
General shape and form. Maples are,
in the main, trees around 6–20 m tall depending on the species. However,
they range from shrubs, such as ‘Dissectum Atropurpureum’ and the other small
forms of the Japanese maples through to forest giants like sycamore, red or
scarlet maple (A. rubrum), silver
maple (A. saccharinum) and the sugar
maple, all of which can exceed 40 m in height. Regardless of size though,
maples are usually well-proportioned trees with interesting branch structure. A
few of the shrubby Japanese maples have twisted branches in the style of the
corkscrew hazel (Corylus avellana
‘Contorta’).
Flowers. Yes, flowers, something
you tend not to think about with maples, though they certainly have them. Not
great big things with showy petals, but tassels of tiny ephemeral blooms that
rarely last more than a week or so. Nevertheless, in some cases they are a real
feature. The flowers are also a source of a pale amber
to green but otherwise unremarkable honey. Acer
negundo var. violaceum is a
relatively well-behaved variety of the suckering, often despised box elder that
is well worth growing for its spring flowers, which appear so delicate against
the soft new spring growth.
Maple bark is highly variable and often very attractive,
especially after the leaves have fallen when it is, naturally enough, far
easier to see and appreciate. Some maples, such as the snakebark maple (A. davidii), have smooth bark with
patterns of colours or stripes, others have peeling bark in warm russet tones
like that of the paperbark maple (A.
griseum).
Those sycamores, the maple seeds and the winged membranes to
which they are attached, are technically known as samara. Most samaras resemble
the common sycamore in shape, although they vary greatly in size. In a few
cases they are an attractive feature in their own right, being brightly
coloured or interestingly shaped.
As to which trees display which features. Well, many fit
into more than one category, so rather than group them by characteristics I’ll
deal separately with each of the main species and some of their cultivars.
Acer buergeranum
Trident maple
Native to eastern China
and Japan, this
round-headed tree grows to around 10–12 m tall and gets its common name
from the leaves, which usually have three lobes, though they can have 5. It is
a relatively slow-growing species. Its autumn colour is primarily red with shades
of orange and yellow. Its and ideal shade tree if you stake
it when young and prune off the lower branches to form a canopy.
Acer cappadocicum
Caucasian or coliseum maple
A 20 m found tree found from the Caucasus
to northern India,
this species is best known for its bright golden yellow autumn foliage.
‘Aureum’ has yellow foliage in spring and autumn; the young stems and spring
leaves of ‘Rubrum’ are bright red. The Caucasian maple often produces suckers
around its trunk, though these are rarely troublesome.
Acer caudatifolium
Formosan or Mt. Morrison
maple
Still often sold under its former name of A. morrisonense, this species from China
and Taiwan is a
fast growing tree that can eventually reach 20 m tall. At all times it is
a very colourful tree. The bark is green with white to cream streaks and the
shallowly-lobed pointed foliage, which is red when young, passes through pink
to light green, then reddens in autumn. It is reasonably hardy but does not do
well in inland areas with hot dry winds or where frosts are severe. It prefers
moist, humus-rich soil.
Acer davidii
Snakebark maple
This 15 m tall Chinese species is mainly grown for its
white-striped and flecked green to purple bark. The young leaves, which are
usually 3-lobed on mature trees but often unlobed, are also white-striped. This
effect fades with age and the foliage develops little colour before falling.
‘George Forrest’ is a large-leafed cultivar.
Acer griseum
Paperbark maple
Native to China
and reaching 5–10 m tall, this truly is a year-round maple. In spring it
has striking bright green new growth that darkens in summer, in autumn it often
develops red tones that match the tint of its small samaras, and throughout the
year it has peeling bark in a warm russet brown shade. The papery bark peels
more heavily in winter when it can best be seen.
Acer japonicum
Full-moon maple
Although capable of eventually reaching
12 m tall, this Japanese native is slow-growing and often kept trimmed to
shrubby proportions. The full-moon maple combines foliage and form. it is neat small tree with attractively tiered branches; its
leaves are 7–15 cm wide with 7–11 lobes and can be almost round in some
forms. The autumn colour is a combination of bright red and yellow on a green
background. The fernleaf full-moon maple, ‘Aconitifolium’, has very finely
divided foliage reminiscent of aconite or ranunculus leaves.
The golden full-moon maple, A. japonicum var aureum, has rounded bright lime green spring leaves that become
yellow as they mature then turn golden with red in autumn. It is now more
properly known as A. shirasawanum
‘Aureum’, though it is usually still sold under the A. japonicum name.
Acer macrophyllum
Big-leaf or Oregon maple
Found along the riverbanks of western North
America from Alaska
to southern California, this
fast-growing tree can reach 30 m tall. While it demands space because its
height, large crown and the dense shade it casts, this species is worth growing
for the size of its leaves, which are up to 20 cm long by 35 cm wide,
and for its vibrant orange autumn tones. With leaves like these you’ll never be
short of top quality compost. The flowers are bright yellow and pleasantly
scented.
Acer miyabei
Kuroba itaya
This 8–12 m high
tree native to Japan
is notable for its corky bark, finely hairy blue-green foliage and it bright
golden yellow autumn colour. It is rare in cultivation because of propagation
difficulties.
Acer mono
Painted maple
Rarely seen in New Zealand
gardens, this tree from temperate eastern Asia grows to
around 15 m tall in the wild. It has 5-lobed leaves that are quite
distinctive because the basal lobes are often very small. Because it has little
autumn colour the true species is rarely grown, but if you see the cultivar
‘Hoshiyadori’ buy it immediately. It is a large shrub, around 5–7 m tall,
and has marvellous mottled variegated foliage. While the foliage is prone to
sunburn and tends to revert to green, this is a plant worth persevering with.
Acer negundo
Box elder
Widely naturalised
worldwide this 20 m tree is found in several forms over all of North
America and southwards to Guatemala.
It is a vigorous tree that self-sows freely, a habit that doesn’t endear it to
gardeners. It does not have the typical palmate maple foliage but instead has
pinnate ash-like leaves made up of 3–7 leaflets each up to 10 cm long. The
purple leafed box elder (A. negundo
var. violaceum) has light purple
stems and young foliage and its flower tassels are also purple-tinted, which
makes them stand out more clearly than those of other forms. ‘Flamingo’ has
cream and green variegated foliage that from ‘Variegatum’ in being pink-tinted
when young. ‘Kelly’s Gold’ has yellow spring growth that matures to light
green.
Acer palmatum
Japanese maple
Everyone knows the beautiful Japanese maple with its seemingly
endless range of cultivars in every imaginable leaf shape and colour. Native to
Japan and Korea,
it is an 8–10 m high tree in the wild that has been highly refined and
developed by both Japanese and Western gardeners.
Unfortunately it is a tree that prefers cool humid
conditions. It suffers if exposed to hot dry nor’west winds and the soft
foliage of the fancy cultivars can burn with prolonged exposure to the summer
sun. Root rots can cause a sudden collapse while branch die-back is slower but
also sometimes fatal.
Regardless of these problems the Japanese maple is nearly
everyone’s favourite small tree. The basic species is usually tough and
trouble-free provided the soft spring growth is not damaged by late frosts or
winds. The spring leaf colour varies green to pale gold with the form and the
autumn tones are also variable, covering shades of red, orange, gold and
yellow.
The coloured and cut-leaf cultivars are fussier. Give them
humus-rich well-drained soil in a position where they are protected from the
wind and shaded from the afternoon sun and should eventually succeed.
There are dozens,
possibly hundreds, of cultivars divided into seven main groups with sub-groups.
A lack of space precludes a description of the differences between these groups.
It really doesn’t matter though, because with other than the Dissectum group
(very finely divided toothed leaves) and the Linearilobum group (deeply cut
lobes) and the very dwarf cultivars it would take a real expert to spot the
fine differences between the groups and cultivars.
Nurseries often carry
a large range of cultivars. Be careful of placing too much reliance on the
names they use because they have become confused over the years. It is better
to choose your maples in spring when the foliage has developed and to buy
container-grown specimens so that you can be sure the roots have not been
damaged during transplanting.
Some of the more
common and reliably named cultivars include: ‘Senaki’
or ‘Senkaki’, bright red twigs and red new growth; ‘Bloodgood’, green summer
foliage mottled with red; ‘Aureum’, deep gold autumn leaves; ‘Beni Kagami’,
dark red new growth and bright red autumn foliage; ‘Katsura’, a very dwarf bush
that seldom exceeds 1.5 m high, it has yellow-gold leaves; ‘Hessei’, bronze
and red autumn foliage; ‘Dissectum Atropurpureum’, purple foliage; ‘Dissectum
Variegatum’, green, white and pink foliage; ‘Dissectum Roseomarginatum’,
red-edged leaves; ‘Linearilobum Atropurpureum’, purple-red foliage that becomes
bronze in autumn; ‘Linearilobum Rubrum’ bright red autumn foliage; ‘Butterfly’,
white-edged light green leaves; ‘Shigitatsu Sawa’, shallowly lobed yellow-green
leaves with darker veins; and ‘Ukigomo’, deeply lobed leaves with mottled green
and white variegations.
Acer platanoides
Norway maple
The Norway maple
grows to 30 m tall and is found from northern Europe
to the Caucasus and has become naturalised in North
America. It is a strong-trunked, round-headed tree with 5-lobed
leaves up to 18 cm wide. The summer leaves are deep green and rarely
develop anything more than irregular yellow patches before turning brown and
falling. ‘Columnare’ is a relatively narrow form; ‘Drummondii’ is a beautiful
variegated with light cream leaves sharply edged in cream;‘Goldsworth Purple’, a
purple-leafed form developed by Slocock’s Nursery of England; and ‘Walderseei’
has leaves that are heavily mottled with creamy-white and which turn pale
yellow in autumn.
Acer pseudoplatanus
Sycamore
Largely described
earlier, the sycamore is too large and messy for most gardens but there are
several cultivars suitable for smaller areas. ‘Brilliantissimum’ has foliage
that changes from pink through this yellow to green as it matures in spring and
summer; ‘Purpureum’ has deep green leaves with purple undersides; and ‘Erythrocarpum’
has showy red samaras.
Acer rubrum
Red, scarlet or swamp maple
Native to the eastern United
States, this fast-growing 20 m tall
tree has bright reddish-pink flowers in spring and vivid red samaras in autumn.
The leaves are up to 10 cm wide with 3–5 lobes and colour well in the
autumn, developing intense red and gold tones. This species is occasionally
tapped for its syrup. ‘Columnare’ is a broadly columnar cultivar, not to be
confused with A. platanoides
‘Columnare’. Although I have not seen it flower or fruit under Christchurch
conditions, I’m sure it must. ‘Red Sunset’ has particularly good autumn
foliage.
Acer saccharinum
Silver maple
Often confused with the sugar maple because of their similar
botanical names, the silver maple is quite similar in appearance too. Found
over much of eastern North America, it grows to around
40 m tall and has an open crown. It is fast-growing, tolerates drought and
flood and is sometimes used as quick shade tree in harsh conditions. Its large
leaves have silvery undersides and are red, orange or gold in autumn.
Acer saccharum
Sugar maple
As mentioned earlier
this species, widespread in North America, is both a
timber tree and the source of maple syrup, which makes it the most commercially
important maple. Although you might think, considering its colour on the
Canadian flag, that the autumn foliage would be red, in fact it is quite
variable. And that’s not just from season to season but from tree to tree. Some
do have red autumn leaves; others may be orange, gold or combinations of
colours. Bigtooth maple (A. saccharum ssp.
grandidentum) has deeply lobed,
thick, glossy green leaves with blue-white undersides. Sugar maple is not a
good tree for high traffic areas as its roots suffer in compacted soils.
Acer tataricum
Tatarian maple
This 10 m tall tree is found over much of the temperate
area of the northern hemisphere except Europe. It has
small leathery green leaves that develop white flecks in summer then turn
yellow in autumn. In spring it produces fragrant creamy yellow flowers that are
later followed by red samaras.
The Amur maple (A.
tataricum ssp. ginnala) is found
through Siberia and northern China
to northern Japan,
this shrubby tree 5–8 m tall tree is extremely tolerant of wind and cold.
It used to be classified as a distinct species, A. ginnala, and is often still sold under that name. It is a neat,
compact tree with vivid red autumn foliage. In areas where A. palmatum suffers it makes an effective substitute.
******
Except for a very few rarely grown species, maples are hardy
throughout New Zealand.
In fact, northern areas may be too mild for some, at least as regards seeing
the best autumn colours. Apart from an intolerance of hot dry winds, maples are
generally undemanding trees that adapt well to cultivation. That’s why there
are so many to choose from. Provided you choose wisely, considering the size of
the tree and the features you prefer, maples should give you years of
trouble-free pleasure and an abundance of superb leaf mould.
Copyright Geoff Bryant
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