Few plants are so sought after as rare Japanese maples and yet as far as collecting is concerned we westerners are what I would politely term as relative newbies. By way of example, during the Edo period in Japan (1603-1868) there were already over 250 varieties of Acer palmatum that had been selected and cultivated. Currently there are in excess of 1,000 cultivars available and hardly a day goes by at the nursery when I am not asked for one of these rarities. So I thought I would dedicate an entire article to the intricacies of this species, while also including two more that are often mistaken for it , both of which are known by the common name Fullmoon maple – those being Acer shirasawanum and A. japonicum.
More than Just a Name
I often get complaints about the complexity or difficult pronunciation of the Japanese cultivars but I think a quick translation will give you an appreciation of their beauty. While some of these such as ‘Koto-no-ito’ (harp strings), ‘Sango kaku’ (coral tower), ‘Osakazuki’ (leaf like a Saki cup), ‘Ukigomo’ (floating clouds) and ‘Seiryu’ (blue-green dragon) serve as straight descriptors, other cultivar names are melodic like a haiku poem. A few good examples of these would be ‘Asahi zuru’ (the dawn swan), ‘Shojo shidare’ (cascading red-faced monkey), ‘Hoshi kuzu’ (star-studded sky), ‘Beni komachi’ (beautiful red-haired little girl) and my favourite ‘Oridono nishiki’ (richly coloured fabric of the master). Semantics aside, there are other good reasons to pay close attention to the proper species and cultivar name as they provide clues to both foliage colour and form. By way of example, the term dissectum usually refers to weeping forms while ‘Aureum’ denotes gold foliage.
Care of Japanese Maples
Although they are not difficult to maintain, Japanese Maples have specific growing requirements. The first and most important of these is well-drained soil, as wet conditions will almost always result in their demise during our often soggy winters. Their preference is for a lightly acidic pH (which is not a problem here on the coast) with some organic matter. Planting depth is also critical, as even a few inches of buried stem will quickly rot the bark; so always plant at the top of the root flare, no deeper. While they tolerate quite a range of exposures from open shade to full sun, some varieties will scorch in hot exposed sites while red-leaved forms will fade to a bronze-green when planted in shade. Fertilize once in spring, usually April, using a balanced or slow release (10-10-10 or 14-14-14) formulation. For pruning you need to use a light hand, so choose a smaller cultivar rather than one that will require constant clipping to keep it in check. Remove dead wood in late February when it is easy to see and do any light structural pruning at the same time. For maximum growth reduction, prune immediately after the sap stops running and the leaves have opened to their full size, often in May. Almost all Japanese maples are grafted, so you are going to have to remove any vigorous green suckers that appear from below the graft or they will quickly overwhelm the top portion. One last note on pruning is to sterilize your tools (secateurs, loppers, saws) between trees using rubbing alcohol, Lysol or 10% bleach in water to prevent the spread of Verticillium wilt; which is one of the few fungal problems that we have to contend with. I consider most Japanese maples hardy to USDA zone 5, although some varieties will thrive in slightly colder regions when given the right microclimate.
Some people are under the impression that these cultivars stay small, but what they lack in height they more than make up for in width – so don’t plant them too close to the sidewalk or driveway where they will need to be hacked bluntly on one side as this ruins the natural form; an option in constrained planting areas is to use the slower growing ‘Red Filigree Lace’ with its very finely cut foliage. At the other end of the spectrum is Acer japonicum ‘Green Cascade’, a monstrous specimen with large green leaves that shift to a vibrant orange in fall; as this one can grow 6-8’ tall by 10-12’ wide at maturity it is best used on large banks. Your standard red-leaved cultivars for the home garden include ‘Garnet’, ‘Red Dragon’, ‘Inaba Shidare’, ‘Ever Red’ and ‘Tamuke yama’, while the less popular green forms such as ‘Waterfall’ and ‘Viridis’ actually have spectacular fall foliage. For a little colour variation try the ever-changing ‘Orangeola’ (orange, red and green) or ‘Pink Lace’ which emerges with subtle rose margins.
A Blast of Spring Colour
Japanese Maples can often rival the best spring flowering shrubs or trees with their vibrant leaf flush. Probably the most highly sought after cultivars are ‘Katsura’ (left) and ‘Orange Dream’ with their brilliant yellowish-orange new growth – both are also modestly sized, maturing at around 12-15’ tall. Acer shirasawanum ‘Aureum’ or Golden Fullmoon Maple makes a similarly impressive spring display of bright chartreuse, although this cultivar will scorch when planted in hot, exposed sites. The reticulated foliage of the Ghost Series (‘Sister Ghost’, ‘Purple Ghost’), ‘Peaches and Cream’ and ‘Aka Shigitatsu sawa’ (also known as ‘Samurai’) all have a myriad of spring colours with contrasting veining; with the latter cultivar often appearing bronze at times. Last on our list of spring spectaculars is ‘Shin deshojo’ with its eye-popping crimson-pink flush that never fails to turn heads.
‘Purple Ghost’, Acer shirasawanum ‘Aureum’, ‘Shigitatsu sawa - aka ‘Samurai’, ‘Sister Ghost, ‘Shin deshojo’, ’Peaches and Cream’ - Copyright 2016 MK Lascelle
Fiery Fall Foliage
There is one ‘king’ of fall foliage among Japanese maples and that is ‘Osakazuki’ (right), which shifts from a relatively mundane deep green to fire engine red so quickly in autumn that if often looks like an entirely different tree. As an aside, it also has bright red samaras (seeds) in late summer that are a feature in their own right. The Acer japonicum genus also really comes into play here with the green leaved ‘Aconitifolium’ (Fern-Leaf Maple) and ‘Vitifolium’ (somewhat resembles grape foliage) shifting to shades of brilliant scarlet, often starting on the margins. ‘Emmett’s Pumpkin’ is another worthy cultivar as it flushes a pale orange in spring and turns an intense red to burnt orange in the fall. I’d like to give another nod to the green-leaved weeping Japanese maples like ‘Waterfall’ or ‘Viridis’, because when given enough sun (shade will subdue your autumn foliage) they turn a consistent bright yellow, dazzling orange or even a brilliant carmine, depending on the season.
‘Emmett’s Pumpkin’, ‘Waterfall’ - Copyright 2016 MK Lascelle
With the exception of very large cultivars, most Japanese maples adapt well to container culture. There are, however, a few prerequisites which include using a container no larger than twice the size of the root ball with adequate drain holes and pot feet to keep it off the ground. Also you will need to blend a compost-based container soil 50/50 with aged pine bark as your soil medium and use fertilizer sparingly, with a slow-release 14-14-14 applied at half rate in April being your best bet. The choices are many and include Lion’s Head Maple (‘Shishigashira’) with its dense green foliage, the stunning ‘Shirazz’ with its variegated leaves of cherry red, pink and white or the diminutive ‘Earthfire’ with its strawberry red foliage. The Linearilobum Group are also good candidates here with their fine thread-like leaf lobes; a few burgundy forms include ‘Red Pygmy’, ‘Villa Taranto’ and ‘Red Spider’. Last but not least are two witches broom mutations, ‘Kandy Kitchen’ and ‘Shaina’, both of which require little pruning to maintain their form.
‘Shirazz’, ‘Shishigashira’, ‘Earthfire’, ‘Red Pygmy’ - Copyright 2016 MK Lascelle
Japanese maples have fibrous root systems, which means that they are not prone to damaging hard surfaces such as sidewalks and driveways, making them ideal for smaller urban gardens. ‘Bloodgood’ (left) with its consistent burgundy-red foliage has long been the standard and matures at around 25’ tall. A dwarf version of this is also available, with ‘Fireglow’ reaching 12’ at maturity. ‘Emperor 1’, ‘Atropurpureum’ (somewhat variable in foliage) and ‘Trompenburg’ are also standard red uprights, with the latter having glossy purplish leaves at spring flush. The Coral Bark maple (‘Sango kaku’ or ‘Senkaki’) brightens up the winter garden with its brilliant coloured stems that intensify with the cold weather. For smaller green-leaved forms you may want to consider ‘Koto-no-ito’ (thread-like leaf lobes) or ‘Seiryu’ (upright laceleaf form), which mature at 10’ and 15’ respectively.
Well this brings us to the end of our tour of Japanese maples which was by no means extensive, as that would have taken much more time. I just wanted to give you a taste of what’s available out there, keeping in mind that your best selection will always be in spring or early fall. Please remember that it is impossible for any garden centre to stock all of these, so if you see a rare maple you like I suggest that you buy it ‘sight on seen’ because those who wait are often disappointed.