Acer JAPONICUM

Acer JAPONICUM - Japanese maple, Acer japonicum.

Can be grown in bonsai style!

Maple is a genus of deciduous trees and shrubs in the family Sapindaceae, comprising more than 120 species and numerous ornamental forms. Native ranges encompass Europe, Asia, and North America, with the greatest species diversity observed in Eastern Asia. Maples are found in mixed forests, on mountain slopes, in river valleys, and in park landscapes. The second genus of the family - Dipteronia - is distributed only in China.

The plants have a rounded or broad dense crown and large palmate-lobed leaves with radiate venation. In autumn, the leaf blades take on vivid shades of yellow, orange, purple, or reddish-brown color, thanks to which maples are considered among the most ornamental trees of temperate climates. The shoots are usually pale, with various shades of bark on young growth.

The flowers are small, yellow-green, gathered in loose inflorescences and appear in early spring - simultaneously with the leaves or slightly earlier. The fruit is a double samara consisting of two winged seeds that separate upon ripening and are carried by the wind. The root system is predominantly superficial, which facilitates establishment but makes the plant sensitive to soil compaction.

Maple reproduces by seeds and suckers. Most species are light-demanding, tolerate urban climates well, and are characterized by longevity: the average lifespan is 150-200 years, and individual specimens can reach an age of 300-500 years. Thanks to ornamental appeal and resilience, the genus is widely used in landscape gardening worldwide.

Japanese maple is a plant with beautiful, graceful leaves. Leaf color changes throughout the entire growing season - from spring to autumn. If in spring and summer they are bright green, in autumn they turn burgundy, cherry, orange, and yellow. Unfortunately, this species is not characterized by high frost resistance; in northern regions it can only be grown in greenhouses and winter gardens in tubs.

Maple seeds are samaras about 1-1.5 cm (0.4-0.6 in) long, ripening in different seasons. Most species even under optimal conditions have a natural germination rate of 20-50%. Simply remaining in the soil, they may germinate only years later.

Scarification significantly increases germination and swelling of seeds; without breaching the outer coat, germination will be minimal. The outer shell is carefully filed or scratched with a hard tool without damaging the embryo, after which the seeds are soaked for 12-24 hours in warm water with the addition of growth stimulants (SUPERthrive, HB-101, Aminozol, Epin, or Zircon). Subsequent presowing preparation is conventionally divided into 3 scenarios depending on the species.

1. Acer BUERGERIANUM, Acer GINNALA, Acer ELEGANTULUM, Acer MACROPHYLLUM, Acer PALMATUM, Acer PLATANOIDES, Acer SACCHARUM, Acer TATARICUM, Acer TRUNCATUM (and most species absent from the list)

require cold stratification for successful germination. The seeds are placed in a small plastic zip-lock bag, into which slightly moistened peat moss or vermiculite is added beforehand, from which water should not be squeezed out under pressure. Air is removed with a palm motion from the bottom to the zipper, the bag is tightly closed and placed in the refrigerator on the lower shelf. Stratification is carried out for 2-4 months at a temperature of 3-5 °C (37-41 °F). Once every 1-2 weeks the contents are checked. If condensation appears, excess moisture is removed by gentle pressing, after which the bag is flipped. In case the substrate dries out, 1-2 drops of water are added. After germination begins, seeds are taken out of the refrigerator and planted into prepared soil.

2. Acer CAMPESTRE, Acer GLABRUM, Acer GRISEUM, Acer JAPONICUM, Acer PSEUDOSIEBOLDIANUM, Acer SHIRASAWANUM (and complex rare/mountain/Asian species)

due to germination difficulty have an additional stage of warm stratification. After scarification and soaking, the seeds are kept in a warm room at a temperature of 20-30 °C (68-86 °F) for 2-4 months. Next, the seeds are placed in a plastic bag and undergo cold stratification (as described in point 1), sometimes with a repeat of the cycle. One should not be surprised by low germination; realistic expectations are only about 20-30%. After germination begins, seeds are planted into prepared soil.

3. Acer RUBRUM, Acer SACCHARINUM (and hybrids such as Acer × FREEMANII)

do not require stratification and are sown immediately after scarification and soaking.

After any of the preparatory stages, seeds are sown in a light, air-permeable substrate to a depth equal to the size of the seed or with a planting depth of 0.5-1 cm (0.2-0.4 in), moistened from a spray bottle, placed in a greenhouse or covered with film, and germinated in light, but not in direct sun at a temperature of 18-22 °C (64-72 °F). Seedlings need ventilation. Overwatering and drying out of the sowings must be avoided.

Seedlings appear after 2-4 weeks; the maximum germination period may exceed 6-8 weeks, and some seeds may germinate only in the 2nd-3rd year. After the unfurling of the first true leaves, pricking out into individual pots is carried out. Cultivar forms are also propagated by grafting onto hardy rootstocks to preserve ornamental coloration.

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Maple prefers sunny or semi-shady areas where ornamental leaf color is displayed most vividly. The plant tolerates urban conditions well and is resistant to wind and smoke. In the first years after planting, regular soil moistening and mulching of the tree well are recommended to preserve moisture. The best results are achieved on fertile, loose, and moderately moist soils with good drainage.

Watering is carried out regularly during hot and dry periods, approximately 10-15 l (2.6-4 gal) per plant, and after planting - a double amount. In ordinary years watering is performed once a month, during hot periods - once a week. Maple can tolerate short-term soil dryness, but full growth is achieved with stable moisture. The plant has a shallow root system, so loosening is carried out carefully and shallowly. After planting, the tree well area is mulched with a layer of 3-5 cm (1.2-2 in).

In early spring, sanitary and formative pruning is performed: damaged, thickening, and diseased shoots are removed. In variegated forms and cultivars with vivid leaf coloration, green shoots may appear, which are cut out to the base so that they do not suppress the ornamental part of the crown. Fertilizers are applied annually: in spring - complete fertilizers with moderate nitrogen content, in summer - phosphorus-potassium mixtures promoting shoot hardening.

Most maples are winter-hardy and do not require winter protection. In harsh winters, it is recommended to protect young plants by mounding the root collar area with leaf litter or spruce boughs. When one-year shoots suffer frost damage, spring pruning is performed - the crown recovers successfully through new growth. With age, the plant's winter hardiness increases.