Acer crataegifolium is a small maple tree native to Japan. Acer crataegifolium is in the snake bark group of maples and hence has white striations in the bark (inconspicuous). The deep green leaves are oval with 3-5 slight shallow lobes. Fall colors are filled with yellows and oranges. This lovely maple will grow to about 24′ but often less.
I. Appearance and Characteristics
Acer crataegifolium (Hawthorn maple, hawthorn-leaf maple or uri maple; Japanese: ウリカエデ urikaede, “melon maple”), is a species of maple in the snakebark maple group, native to mountains forests of central and southern Japan, on Honshū (Fukushima southward), Kyūshū, and Shikoku.
It is a deciduous small tree or shrub that grows to a height of 5–10 m, with a trunk up to 30 cm diameter. The bark is green to greenish-brown, with narrow vertical white or pale grey stripes; the young shoots are slender, green to purplish-red and the buds purplish-red. The leaves are 5–8 cm (rarely to 15 cm) long and 4–7 cm broad, dark green to bluish green and often tinged reddish above, paler green below, ovate-triangular, and may be either unlobed or three-lobed; the petiole is red, 2–3 cm long. The flowers are small, pale yellow, produced on arched to drooping racemes 3–5 cm long. The fruit is a paired samara 1–2 cm long, pink or red maturing brown, with nutlets not more than 4 mm wide.
There are two varieties:
- Acer crataegifolium var. crataegifolium. Leaves up to 7 cm long.
- Acer crataegifolium var. macrophyllum Hara. Leaves up to 15 cm long.
- The Japanese name urikaede refers to the bark pattern resembling the skin of a melon, as also in the similar bark of Acer rufinerve (urihadakaede). The scientific name derives from the supposed resemblance of its leaves to those of hawthorns (Crataegus), though this is somewhat fanciful, only making sense if certain species of hawthorn are considered.
II. How to Grow and Care
Sunlight
The hawthorn maple has a certain requirement for sunlight and prefers a partially shaded area. In cases of exposure to direct sunlight in the summer, the leaves of most varieties will wither, so shading is required. As the plants get older and their root system grows, this condition will be less of a problem. A few varieties will tolerate exposure to direct sunlight, such as ‘Beni Maiko’ and ‘De Shojo’. Some weeping varieties can also tolerate exposure to direct sunlight, such as ‘Ao Shidare’.
Sunlight conditions will directly affect the ornamental appearance of hawthorn maple leaves. In the spring, sufficient sunlight will make the maple leaves more vivid, while in cases of insufficient sunlight or partial shading the leaf color may fade. During the fall, sunlight can also affect the leaf color. For potted plants, full exposure to sunlight is recommended during the spring and the fall, with partial shading in the summer.
Temperature
The hawthorn maple has good cold resistance and is able to tolerate low temperatures. The hawthorn maple is native to the margins of forests in China, Japan, and North Korea, so these trees generally prefer a humid environment. Most hawthorn maple plants have shallow root systems, so they should be watered frequently during the summer. For some varieties, a sprayed mist should be provided during the summer to increase the humidity of the air around them.
Watering
Originating from the temperate regions, hawthorn maple has adapted to a moderate moisture regime, thriving in well-drained soils with consistent moisture. It displays a preference for evenly moist conditions but can endure short dry spells. Watering is optimal once every 1-2 weeks, aligning with its tolerance for slight variations in water availability. Typically cultivated outdoors due to its size and growth habit, hawthorn maple benefits significantly from mulching which helps retain soil moisture and mimics the leaf litter of its natural woodland settings.
Soil
The hawthorn maple does not have many specific requirements for soil. It is a forest native, so it prefers well-drained soil that is rich in humus and slightly acidic. Its main root will extend deep into the soil, but its tiny fibrous roots will be concentrated near the soil surface, so accumulated water in the soil tends to cause root rot.
Fertilizing
Potted seedlings should be given slow-release fertilizer only. For seedlings grown in gardens, fertilizer should be applied three times a year: once in the early spring, once in early summer for the growth period, and once in the fall.
Planting Instructions
The best time for planting or transplanting a hawthorn maple is following defoliation in the fall. At this time, the leaves will have fallen off so there is little transpiration and water loss can be avoided. In addition, the root system will still be growing at this time, preparing for regrowth the following spring. Transplanting should be avoided on the coldest days because cold wind can kill some of the shoots and branches. During the winter, in areas that cannot be sheltered from the wind, it is recommended to cover the branches.
Pruning
Pruning is mainly used to enhance internal ventilation, improve shoot formation, promote growth, and for shaping. The common approach to pruning is to remove any old or weak branches, remove any branches that disrupt the shape of the tree, and remove any branches that cross other branches. Pruning is used to control the plant according to the required height and shape. Generally, this follows the “Y-type” pruning method.
It is possible to prune a hawthorn maple throughout the year, but the coldest winter months should be avoided to prevent damage to the plant. Major pruning to shape a maple can be performed following defoliation in the fall, or prior to leaf growth in the spring. It is recommended to prune in the fall because withered and full buds can be easily distinguished.
According to the shaping plan, you can prune any withered buds and keep the full ones, thus making your tree healthier. For pruning in the summer, diseased, weak, or dead branches can be removed, mainly to enhance the tree’s ventilation.
If grown as a potted plant, the roots can easily occupy the entire flowerpot due to the limited space. This can make a hawthorn maple prone to aging if an old flowerpot is not changed. It is recommended that old roots are pruned during the dormancy period, that is, cut off any old, coarse, diseased, and weak roots.
Propagation
Common propagation methods include grafting, taking cuttings, and sowing seeds.
Grafting is the most common propagation method. Seedlings of Acer palmatum or Acer oliverianum are usually selected for the rootstock. Grafted seedlings have strong roots and grow rapidly, but poor affinity is occasionally present in some cases. Seedlings with Acer oliverianum as the rootstock are less hardy.
Cuttings take longer to grow and are mostly used in the production of bonsai.
Sowing seeds is a common way to cultivate new varieties. The hybrid offspring of two different maples are sown and valuable individuals are then selected from the seedlings. The traits of the parents may not be maintained in the selected offspring.
