Origin
Malus ×arnoldiana (Rehd.) Rehd. is a hybrid apple cultivar that was developed in the early 20th century by the renowned American horticulturist, Luther Burbank. The plant is a cross between Malus baccata and Malus floribunda, both of which are native to central and eastern Asia.
Common Names
The plant is commonly known as Arnold crabapple or Arnold's apple, named after the famous American plant explorer, E. H. Arnold, who collected the original seedlings from the wild in northern Japan and brought them to America for breeding purposes.
Uses
The Arnold crabapple is highly valued for its ornamental qualities and is often planted in gardens, parks, and along streetscapes. The plant is known for its profuse and showy blossoms in spring, which are usually pink or white, and its glossy foliage that turns to a deep bronze or red in autumn. The small, red or yellow fruit that appear in autumn are relished by birds and can also be used for making jelly or cider, although they are quite tart and seedy.
In addition to its aesthetic appeal, the Arnold crabapple is also valued for its hardiness and disease resistance. The plant is particularly resistant to apple scab, a common fungal disease that affects many apple cultivars, making it a popular choice for growers looking for low-maintenance, disease-resistant trees.
General Appearance
The Arnold crabapple is a small deciduous tree that typically grows to a height of 15 to 25 feet and a spread of 10 to 20 feet. The plant has a round or spreading crown with a smooth, gray-brown bark that becomes more rough and textured as the tree ages. The alternate, ovate foliage is dark green and glossy with serrated edges, and turns to an intense reddish or bronze color in the fall. The flowers are produced in clusters and consist of five petals that are pink or white in color and have a pleasant fragrance. The fruit is a small, round pome, about 1 inch in diameter, that is usually bright red or yellow, although some varieties can be green or russet. The fruit is tart and mealy, and ripens in late summer or early fall.
Light Requirements
The Malus ×arnoldiana plant requires full sunlight exposure to grow healthily. You need to provide it with at least 6 hours of direct sunlight each day. This plant cannot thrive in the shade or low light conditions, so ensure you plant it in an open space that receives maximum sunlight.
Temperature Requirements
The suitable temperature range for the Malus ×arnoldiana plant is between 60 to 70°F (15 to 21°C). Temperatures below 50°F (10°C) can significantly damage the plant. The plant remains dormant during winter, and temperatures below 32°F (0°C) do not affect it. During the spring and summer, the plant needs warmth but can still thrive in hot temperatures of up to 90°F (32°C).
Soil Requirements
The Malus ×arnoldiana plant thrives in well-draining soil that is rich in organic matter. The soil for this plant should have a pH level ranging from 6.0 to 7.0. Loamy and sandy soils are appropriate for this plant. You should avoid planting the Malus ×arnoldiana in areas with compacted, waterlogged, or heavy clay soils. The plant requires adequate soil moisture for healthy growth, so ensure you water it consistently.
Cultivation methods for Malus ×arnoldiana
Malus ×arnoldiana (Rehd.) Rehd., commonly known as Arnold crabapple, needs full sun exposure for the best growth conditions. This plant can tolerate a wide range of soil types, but well-drained soils with a slightly acidic pH are ideal. The plant should be placed on elevated sites to prevent waterlogging. The best time for planting is during the fall or winter, and the recommended spacing is about 15-20 feet apart.
Watering needs
Malus ×arnoldiana requires regular watering, particularly during its early years, to promote proper root establishment. It is best to water the tree slowly and deeply, at least once or twice a week, especially during hot and dry weather conditions. The plant should not be watered excessively, as it can lead to waterlogging and disease development.
Fertilization
Fertilization can help boost the growth and yield of Malus ×arnoldiana. The plant should be fertilized once every year, in late winter or early spring, using a complete slow-release fertilizer. The recommended amount is about one to two pounds of fertilizer per inch of trunk diameter. Nitrogen-rich fertilizers should be avoided, as these can cause excessive vegetative growth and reduced fruit production.
Pruning
Pruning plays a vital role in maintaining the health and appearance of Malus ×arnoldiana. Regular pruning helps to remove damaged or diseased branches, promote proper growth and shape, and increase fruit production. The best time to prune the plant is during late winter or early spring, while it is still dormant. The main goal of pruning is to remove any crossing or rubbing branches, maintain a balanced shape, and remove any suckers that may develop.
Propagation of Malus ×arnoldiana
Malus ×arnoldiana (Rehd.) Rehd., commonly known as Arnold crabapple, is a deciduous tree native to North America. It is a popular ornamental tree due to its beautiful pink flowers and edible fruit. The tree can be propagated using several methods.
Seeds
One of the easiest and most common ways to propagate Malus ×arnoldiana is through seeds. The seeds of the tree should be collected in the fall, cleaned, and then stratified in the refrigerator for three to four months. After stratification, the seeds should be sown in pots and kept in a cold frame until they germinate. Once the seedlings have grown, they can be transplanted outside.
Cuttings
Another way to propagate Malus ×arnoldiana is through cuttings. Hardwood cuttings should be taken from the parent tree during the winter months. The cuttings should be about 6-8 inches long and stripped of their leaves. They should be dipped in rooting hormone and planted in a pot filled with a well-draining soil mix. The pot should then be placed in a warm and bright location and kept moist. The cuttings should root in two to three weeks and can be transplanted outside once they have grown.
Grafting
Grafting is a more advanced method of propagation and is often done by experienced gardeners. Malus ×arnoldiana can be grafted onto a rootstock of a related apple tree. The scion should be taken from the parent tree during the winter months, while the rootstock should be chosen based on its hardiness and disease resistance. The scion and rootstock should be carefully grafted together, and then the tree should be grown in a greenhouse until it is established.
Air Layering
Air layering is a propagation method that involves rooting a branch of the parent tree while it is still attached to the tree. This method should be done during the spring or early summer months. A branch should be chosen, and a small section of the bark should be removed. The exposed wood should then be treated with rooting hormone and wrapped in damp sphagnum moss. The moss should then be wrapped in plastic wrap, and the process repeated until the entire branch is covered. The branch should be left for several months until roots have formed. At this point, the branch can be cut off from the parent tree and transplanted elsewhere.
Disease Management
The plant Malus ×arnoldiana (Rehd.) Rehd. is susceptible to various diseases, including:
- Apple Scab: This fungal disease causes brownish-black spots on the leaves and fruits, leading to premature defoliation and reduced fruit quality.
- Cedar Apple Rust: Another fungal disease that manifests as yellow-orange spots on the leaves and fruits, leading to premature defoliation and reduced fruit yield.
- Fruit Rots: This disease is caused by several fungal pathogens and leads to the decay of fruits during storage.
The following disease management strategies can be adopted:
- Planting disease-resistant cultivars
- Practicing proper sanitation, including removing and destroying infected plant materials
- Applying fungicides according to the manufacturer's guidelines
- Avoiding overhead irrigation to reduce leaf wetness and the spread of fungal spores
Pest Management
Several pests can attack Malus ×arnoldiana (Rehd.) Rehd., including:
- Codling Moth: This worm-like insect damages fruits by tunneling inside them.
- Apple Maggots: These small, white maggots feed on apple fruits, causing them to rot.
- Aphids: These small, soft-bodied insects feed on the sap of the plant, leading to stunted growth and reduced fruit yield.
The following pest management strategies can be adopted:
- Practicing proper sanitation, including removing and destroying infested fruits and plant materials
- Using sticky traps and barriers to prevent adult insects from laying eggs on the fruits
- Applying insecticides according to the manufacturer's guidelines
- Encouraging predators and parasites of the pests, including ladybirds and lacewings
