Malus sieboldii, commonly known as Siebold’s crabapple, is a small tree or large shrub native to Japan, Korea, and China. It belongs to the family Rosaceae and is widely grown for its ornamental value. Siebold’s crabapple is a popular choice for gardens, parks, and landscaping due to its beautiful flowers, fruits, and foliage.
I. Appearance and Characteristics
Malus sieboldii, commonly called Siebold’s crab, Siebold’s crabapple or Toringo crabapple, is a species of crabapple in the family Rosaceae. Some botanists have reclassified it as Malus toringo.
Siebold’s crabapple is a deciduous tree or large shrub that can grow up to 10 meters tall but is more commonly 3-5 meters tall. The tree has an upright growth habit and a rounded crown. The bark of the tree is smooth and greyish-brown when young, becoming rough and dark grey as it ages.
The leaves are simple, alternate, ovate to elliptic, and serrated with a glossy dark green color. In autumn, the leaves turn a stunning golden-yellow, adding to the tree’s ornamental value.
The tree produces flowers in spring, which are a beautiful sight to behold. The flowers are white or pinkish and have a diameter of about 2.5 cm. They are arranged in clusters of 3-5 and appear before the leaves emerge.
The flowers give way to small, round, greenish-yellow fruits that are about 2.5 cm in diameter. The fruits mature in late summer and early autumn and are edible, but not commonly consumed due to their sour taste.
It is sometimes considered to have three varieties:
- Malus sieboldii var. sieboldii (the true Siebold’s crabapple)
- Malus sieboldii var. sargentii, which is sometimes considered to be a separate species Malus sargentii
- Malus sieboldii var. zumi
The cultivar Malus toringo ‘Scarlett’ has received the Royal Horticultural Society’s Award of Garden Merit.
Malus sieboldii – Malus toringo is native to eastern temperate Asia, in China, Japan, and Korea.
II. How to Grow and Care
Sunlight
Toringo crabapple prefers sunlight and grows well in full sun. Sufficient sunlight for about 8 hours a day is recommended. Sunlight will have a great impact on flower colors, while insufficient sunlight will lead to lighter colors. If there is strong light in summer, toringo crabapple needs proper shady conditions to avoid high-temperature injuries. Too much light may cause leaf curling or spots on stems and leaves.
Temperature
Widely distributed in the northern temperate zone, toringo crabapple is generally very adaptable to the distinct seasons, including hot summers and cold winters. It can tolerate temperatures as low as -30 ℃. Toringo crabapple can’t tolerate extremely high temperatures in summer; temperatures above 32 ℃ will affect its growth. The tree is drought-tolerant and doesn’t require much water, hence, avoid over-watering it.
Watering
Toringo crabapple thrives in conditions that mimic its origin, where periodic rainfall and moderate humidity prevail. This species exhibits a preference for consistent moisture but is adaptable to brief dry spells, reflecting a balanced water habit. Watering should occur once every two weeks to maintain this equilibrium. Typically grown outdoors due to its size and ornamental nature, toringo crabapple enters a dormant phase during colder months which reduces its water requirements, aligning with the natural decrease in winter precipitation.
Soil
Toringo crabapple can adapt to various soils. The most suitable soil for growth is slightly acidic or neutral, humus-rich, loose, well-drained, and sandy. The best pH range for the soil is 6-8. During cultivation, the soil can be mixed with garden soil, peat soil, and organic fertilizer in a proportion of 6:3:1.
Fertilizing
To encourage robust growth and vibrant blossoms in toringo crabapple, apply a balanced fertilizer, rich in N-P-K, every 6-8 weeks during the growing season. Utilize half the recommended dosage for container plants, and a full dose for in-ground toringo crabapple, ensuring to water thoroughly post-application. Over-fertilizing can harm toringo crabapple, causing foliage burn and weak growth. In dormancy, withhold fertilization to avoid stimulating growth during rest. Monitoring soil fertility helps tailor fertilization to toringo crabapple’s life cycle for optimal health.
Planting Instructions
It is generally easiest to plant toringo crabapple by buying seedlings rather than sowing seeds. The recommended planting time is before budding in early spring or after leaves fall in early winter. Before planting, thoroughly check whether the roots of the tree are healthy. If rotten roots are found, they need to be quickly cut and disinfected with carbendazim.
When planted in a garden, the pit depth should be about 40 cm and the diameter about 60 cm. If the root is large, the size of the pit needs to be twice as big as the root ball. Before transplanting, apply some rotten organic fertilizer as the base fertilizer. In severe cold zones, pay attention to keeping toringo crabapple warm while transplanting. Add a cover such as wood chips or mulch at the base of the plant to ensure it overwinters safely.
Pruning
Pruning is very important for toringo crabapple and is usually performed between late fall after its leaves drop and early spring before it sprouts. Pruning not only keeps branches scattered and maintains the tree’s shape, but also ensures ventilation and sunlight transmission, which is conducive to its growth. Promptly cut off dense, overlapping, thin, and infected branches, or prune out a suitable and aesthetic shape based on the viewing environment.
When blooming, you can also cut off some branches and cut away withered flowers to promote budding and the blossoming of new branches.
When pruning and cutting longer branches, leave enough new buds for branches to grow better afterward.
Propagation
A deciduous tree valued for its ornamental features, toringo crabapple’s cultivation can be efficiently achieved through grafting. This technique allows for genetic consistency and healthier stock, where a piece of toringo crabapple is joined to a robust root system, fostering strong growth. Expertise is vital, as a specific cut ensures successful adhesion and a swift healing process. For optimal results, a grower should use high-quality rootstocks and maintain sterile conditions to prevent disease transfer.
Transplanting
The perfect time to transplant toringo crabapple is during the ‘S2-S3’ stage, best described as late winter to early spring, marking a dormant phase which encourages healthy regrowth. Choose a sunny to half-shaded spot with well-drained soil for transplanting. Remember, toringo crabapple prefers a slightly acidic pH.
Pests and Diseases
Like all plants, Malus sieboldii is susceptible to various insect pests and diseases. The most common pests that affect the tree are aphids, scales, and spider mites. These pests can be controlled with insecticides or by introducing natural predators such as ladybugs and lacewings.
The most common diseases that affect the tree are fire blight, apple scab, and powdery mildew. Fire blight is a bacterial disease that causes the leaves and branches to turn black and wilt.
Apple scab is a fungal disease that causes brown spots on the leaves and fruit. Powdery mildew is a fungal disease that causes a white, powdery growth on the leaves and fruit. These diseases can be controlled with fungicides, proper sanitation, and good cultural practices.
III. Uses and Benefits
- Ornamental uses
Malus sieboldii is widely grown as an ornamental tree in gardens, parks, and landscaping.
Siebold’s crabapple is also used for bonsai cultivation due to its small size and ornamental value. The tree is a popular choice for bonsai enthusiasts because it responds well to pruning and can be trained into different shapes and styles.
- Other uses
The fruits of Siebold’s crabapple are not commonly consumed due to their sour taste. However, they can be used to make jellies, preserves, and cider. The tree is also used in traditional medicine for its antiseptic and astringent properties.
