How Many Japanese Maples Are There?

When you go to the gardening store, you see so many different kinds of Japanese maples and might be wondering how many there are exactly.

By species, there are two Japanese maples: Acer palmatum and Acer amoenum.  By classification of cultivars, there are seventeen Japanese maples.  By the number of cultivars, there are around 1000 Japanese maples in the world.  

Japanese maple: species

Maple trees in the world

Maple (genus: Acer) is one of the most diverse and widespread kinds of trees in the Northern hemisphere.  There are 124-156 maple species in the world, 80% of which are native to Asia.  Japanese maples are among those maples and there are 30 Acer (maple) growing naturally in Japan.

Number of Japanese maple species

What is “Japanese maple”?

When you hear the word “Japanese maple”, you probably think of a tree with pointed, deeply-lobed, serrated leaves like in the picture below.

In fact, this deeply-lobed maple tree is called “Momiji” in Japanese and is one of the two kinds of maples native to Japan.  The other one is called “Kaede“.  Most Kaede maples have leaves like sugar maples; slightly lobed with shallow incisions.

So, maple trees native to Japan can be divided into 2 groups: Momiji maple and Kaede maple.  Momiji maples are those which have pointed, deeply lobed, serrated leaves, which usually indicate “Japanse maples”.

Momiji maple (Japanese maple)

(Source)

Among 30 Acer (maple) species growing naturally in Japan, there are only 2 Japanese maple species: Acer palmatum and Acer amoenum.  The latter Acer amoenum is further classified into two sub-varieties, Acer amoenum Carrière var. amoenum and Acer amoenum Carrière var. matsumurae∗.

1. Acer palmatum
2. Acer amoenum
    – Acer amoenum Carrière var. amoenum
    – Acer amoenum Carrière var. matsumurae

∗According to genetic research, Acer amoenum Carrière var. amoenum and Acer amoenum Carrière var. matsumurae are genetically indistinguishable from each other in domesticated cultivars, whereas the genetic difference between Acer palmatum and Acer amoenum is significant.  (Source: 神崎 真哉, 井上 紘一, 宇都宮 直樹, 矢野 正善, SSRマーカーを用いたモミジの品種同定と遺伝的類縁関係の解析, 園芸学研究, 2013, 12 巻, 1 号, p. 1-7)

Because of their beautiful leaf colors and interesting leaf shapes, these Momiji maples have been cultivated for hundreds of years in Japan to have more desirable traits.  In fact, all of the traditional Japanese maple cultivars are derived either from these two maple species: Acer palmatum and Acer amoenum.

Kaede maple

As to 27 Kaede maples, not much has been done to develop cultivars compared to Momiji maples (=Japanese maples).  There are about a dozen cultivars with spots or of different shapes from the originals, but they are not actively grown in and outside of Japan by gardeners.

Japanese maple: cultivars classification

Groups of Japanese maple cultivars

According to The Maple Society, Japanese maple cultivars can be classified into the following 17 groups.  This classification is organized by the color and shape of leaf, the color of the branches as well as the texture of the bark.

Group Name	Description	Example
1: Amoenum	Ordinary Japanese maple with no distinctive characteristics that assign them to other groups	Ohsakazuki
2: Atropurpureum	Upright growing with red foliage	Bloodgood Yasemin
3: Aureum	Yellow/orange spring foliage eventually turns yellow/lime green in summer	Katsura Summergold Jordan
4: Convexum	Leaf with convex lobes	Trompenburg Pévé Starfish
5: Corallinum	Bright pink spring color	Deshojo Ruben
6: Crispum	Relatively small five-lobed curly leaves	Shishigashira Krazy Krinkle
7: Dissectum	Deeply divided leaves till the base of the leaf, doubly serrated lobes, mostly weeping	Seiryu Garnet Dissectum
8: Linearilobum	Extremely narrow lobes divided to the leaf base	Koto-no-ito
9: Matsumurae	7- to 9-lobed leaves divided to the leaf base, but not as strongly doubly serrate and without the weeping mushroom habit of the Dissectum Group	Soma-no-kawa
10: Marginatum	Leaf margins distinctly different in color from the rest of the leaf (eg. white vs. green)	Kagiri-nishiki Butterfly
11: Palmatum	No particular characteristic other than 5 lobed (occasionally 7) leaves, divided to no more than two-thirds of the leaf	Diane
12: Pinebark	Rough pine-like bark	Nishiki-gawa
13: Red wood	Bright red or orange winter branches	Sango-kaku
14: Reticulatum	Leaf veins distinctly different in color (green/red) from rest of the leaf	Aka-shigitatsu-sawa Nathan
15: Sessilifolium	5-lobed leaves without a petiole and lobes reduced at the base to a petiole-like attachment	Beni-hagoromo Hazenoiro
16: Variegatum	All other variegated Japanese maples not in the Marginatum Group (#10)	Uki-gumo
17: Witches Broom	Reduced central lobe, restricted growth	Carlis Corner Broom

(Source: The Maple Society)

1: Amoenum

2: Atropurpureum

3: Aureum

5: Corallinum

6: Crispum

7: Dissectum

8: Linearilobum

10: Marginatum

13: Red wood

Leaf shape/color and branch pattern of Japanese maples

The following is a comprehensive list of patterns that the current Japanese maple cultivars have; leaf shape patterns, leaf color patterns and branch/vein patterns.

Leaf shape patterns

Japanese maple has 10 leaf shape patterns as follows.

1. Middle lobe reduced and usually shorter than the surrounding lobes
2. Leaf sessile and lobes reduced at the base to the central nerve
3. Lobes convex and usually seven or more lobes
4. Leaf margin wavy or curly, no more than 5 lobes
5. Leaf divided to the base, weeping
6. Leaf divided to half the leaf blade or less
7. Leaf divided to two-thirds
8. Lobes strongly double toothed
9. Lobes only lightly toothed or almost entire
10. Lobes wider and clearly toothed

Leaf color patterns

Japanese maple has 6 leaf color patterns as follows.  Color variations are green, red, orange, yellow and pink.  Sometimes two different colors come together, particularly as leaf margin.

1. Green in summer
2. Red or reddish-green in summer
3. Orange to yellow-green in spring and early summer
4. Pink or pinkish-red in spring and early summer
5. Leaf margin in a contrasting color
6. Variegated leaves not just the margins

Branch/vein patterns

There are 4 branch/vein patterns as follows, which are characteristics of a small number of cultivars.

1. Branches with a pine-like rough structure
2. Winter branches red, orange or yellow
3. Branches green or brown
4. Veins in a contrasting color

(Source: The Maple Society)

Japanese maples: number of cultivars

Number of cultivars: historical change

Japanese maples have been actively cultivated in Japan for a few centuries and in the world since the 19th century.  There are several Japanese books/catalogs dating back to 1710 that showcase Japanese maple cultivars.  According to these books, the following is the number of Japanese maple cultivars at that time.

Date	No. of Japanese maple cultivars∗
1710	36
1882	202
1891	173
1930	219
1967	127

∗ This number includes both Momiji maples and Kaede maples.

The number of Japanese maple cultivars in Japan decreased significantly from 219 to 127 after WW II.  In fact, many of them literally disappeared because, sadly, Japanese maples are used as firewood and their nurseries were mandated for growing food during the war.

Numbers of cultivars: today

Today, Japanese maples are cultivated more enthusiastically outside of Japan due partly to their adaptiveness to different climates.  The exact number of cultivars is unknown because people are producing different kinds of interesting Japanese maples and naming them as new ones that do not necessarily meet the definition to be called a cultivar.

What is a “cultivar”?

According to the International Code of Nomenclature for Cultivated Plants,  a cultivar is defined as an assemblage of plants that (i) has been selected for a particular character or combination of characters, and (ii) remains distinct, uniform, and stable in these characters when propagated by appropriate means.

Some cultivars originate naturally as mutations in plants.  Many old Japanese maple cultivars originated this way and are true to type, meaning propagation by seeds usually produces seedlings with (almost) the same characteristics as the parent tree.

Other more recent cultivars are an artificial hybrid of two different cultivars.  This type of cultivar is usually not true to type.  To have distinct characteristics as a cultivar, it must be propagated through cuttings and grafting.  Propagation by seed usually produces something different than the parent plant.

Numbers of estimated current cultivars

With all being said, there are about 1000 Japanese maple cultivars around the world today, according to the Royal Horticultural Society (“RHS”) database∗.  I suspect some of these do not have distinct, uniform, and stable characters that distinguish them from each other.

∗ There are 1093 results for Acer palmatum and 6 results for Acer amoenum when searched in RHS “Find a plant” page.  Excluding the same cultivar with different names, there are 1003 Japanese maples left on the list. 

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Reference

Gao, J., Liao, PC., Huang, BH. et al. Historical biogeography of Acer L. (Sapindaceae): genetic evidence for Out-of-Asia hypothesis with multiple dispersals to North America and Europe. Sci Rep 10, 21178 (2020)