Collecting Japanese Maples

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.

Acer shirasawanum - Copyright 2019 MK Lascelle

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.

A selection of Japanese maple leaf forms. From top left clockwise; 'Green Cascade', 'Sawa-chidori', 'Emperor 1', 'Butterfly', 'Peaches and Cream', 'Shishigashira', 'Emmett's Pumpkin' and 'Enkan' in the centre. - Copyright 2019 MK Lascelle

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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.

A weeping red Japanese maple overgrown by green rootstock. Copyright 2019 MK Lascelle

Weeping Forms

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.

Acer japonicum ‘Green Cascade’ - Copyright 2016 MK Lascelle
Acer japonicum ‘Green Cascade’ - Copyright 2016 MK Lascelle

Acer palmatum dissectum 'Pink Lace'  Copyright 2016 MK Lascelle
Acer palmatum dissectum 'Pink Lace' Copyright 2016 MK Lascelle

A Blast of Spring Colour