Acer PALMATUM

Acer PALMATUM - Japanese maple, Acer palmatum, Smooth Japanese maple, Palmate maple.

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. Natural ranges encompass Europe, Asia, and North America, with the greatest species diversity observed in East 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 radial venation. In autumn, leaf blades take on bright shades of yellow, orange, purple, or reddish-brown, making maples considered among the most ornamental trees of temperate climates. Shoots are usually light-colored, with varying bark shades on young growth.

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 samara seeds that separate upon ripening and are dispersed by the wind. The root system is predominantly superficial, which facilitates rooting but makes the plant sensitive to soil compaction.

Maple propagates by seeds and basal shoots. Most species are light-loving, tolerate urban conditions well, and are characterized by longevity: average lifespan is 150-200 years, with individual specimens reaching ages of 300-500 years. Due to their ornamental appeal and hardiness, the genus is widely used in landscape gardening worldwide.

Japanese maple is an ornamental deciduous shrub or small tree 3-6 m (10-20 ft) in height, distinguished by an elegant crown and finely cut leaf shape. Leaves are deeply palmately lobed, usually 5-7-lobed, thin and graceful. In summer, they are colored in shades of green, from bright green to dark olive, depending on the cultivar. In autumn, they acquire bright, rich tones - red, orange, crimson, and golden, creating a striking seasonal "flame". Shoots are slender, reddish or green, particularly noticeable in winter.

Flowering occurs in spring and is quite ornamental upon close inspection. Flowers are small, reddish, gathered in raceme inflorescences, often standing out as a contrasting accent against unfolding leaves. After flowering, two-winged samara fruits form, maturing by summer and frequently retaining a reddish tint.

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 seed germination and swelling; without disrupting the upper layer, germination will be minimal. The outer coat is carefully filed or scratched with a hard tool without damaging the seed, after which they are soaked for 12-24 hours in warm water with the addition of stimulants (SUPERthrive, HB-101, Aminozol, Epin, or Zircon). Subsequent pre-sowing preparation is conditionally 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 not in the list)

require cold stratification for successful germination. Seeds are placed in a small plastic zip-lock bag, inside of which lightly moistened peat moss or vermiculite is added beforehand, from which water should not be released when squeezed. 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 bottom 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 turned over. In case the substrate dries out, 1-2 drops of water are added. Once germination begins, seeds are removed from the refrigerator and planted in prepared soil.

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

due to germination difficulty have an additional stage of warm stratification. After scarification and soaking, seeds are left 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 repeated cycle. One should not be surprised by low germination; realistic expectations are only about 20-30%. After germination begins, seeds are planted in 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 seed size or buried 0.5-1 cm (0.2-0.4 in), moistened from a spray bottle, placed in a mini-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 require ventilation. It is necessary to avoid waterlogging and drying out of the crops.

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

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Maple prefers sunny or semi-shady locations where the ornamental leaf color manifests 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 root zone are recommended to retain moisture. The best results are achieved in 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, with double the amount after planting. In normal years, watering is done once a month; in hot periods - once a week. Maple can tolerate short-term soil dryness, but full growth is achieved with stable moisture. The plant has a superficial root system, so loosening is done carefully and shallowly. After planting, the root collar area is mulched with a layer of 3-5 cm (1.2-2 in).

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

Most maples are winter-hardy and do not require winter shelter. In severe winters, young plants should be protected by mounding the root collar area with leaf litter or spruce boughs. If one-year shoots freeze, spring pruning is carried out - the crown recovers successfully through new growth. With age, the winter hardiness of the plant increases.