Origin
Allium cepa L. var. proliferum (Moench) Regel, also known as the walking onion or tree onion, is a perennial plant species and a variety of Allium cepa, belonging to the Amaryllidaceae family. This plant species is believed to have originated from the central Asian region, spreading to all corners of the world through human activities, particularly during the trade routes of the ancient times.
Common Names
The plant has several common names depending on the region, including tree onion, walking onion, Egyptian onion, topsetting onion, winter onion, and perennial onion. In some regions, the plant is also known as the catawissa onion or the Canadian onion.
Uses
The Allium cepa L. var. proliferum (Moench) Regel plant has a variety of uses. First, it is valued as an ornamental plant due to its unusual appearance and structural adaptability. It is also a food crop, and its bulbs are edible. The plant's leaves, flowers, and bulbs are used as ingredients in cooking for their unique flavor and are also used in traditional medicine as an anti-inflammatory and a remedy for minor ailments. The plant is also used in landscaping as a botanical curiosity, adding character to gardens and landscapes.
General Appearance
Allium cepa L. var. proliferum (Moench) Regel has a unique appearance, characterized by its curved vertical stems that give rise to sets of bulblets at their tips. The bulblets form atop the mature onion stalks and weigh them down, causing them to bend to the ground, where they will plant themselves and then produce their own crop of onions. The plant's bulbs resemble those of shallots or garlic and are small, clustered, and irregularly shaped. The leaves of this plant are upright, with a uniform width and a hollow structure, measuring between 20 and 60 cm. The plant's flowers are borne on stalks, and their color ranges from white to pinkish-purple.
Light Requirements
The Allium cepa L. var. proliferum (Moench) Regel plant requires full sun exposure for proper growth and development. It performs best when exposed to at least six hours of sunlight per day. Therefore, it is essential to plant it in a location where it will receive a consistent amount of direct sunlight throughout the day.
Temperature Requirements
The Allium cepa L. var. proliferum (Moench) Regel plant can tolerate a wide range of temperature conditions. It is capable of growing in temperatures as low as 7°C and as high as 32°C. However, the optimum temperature range for this plant is between 15°C to 27°C, where it can grow at its best.
Soil Requirements
The Allium cepa L. var. proliferum (Moench) Regel plant requires well-drained, fertile soil for optimal growth. The ideal soil pH range for this plant is between 6.0 to 7.0. The soil should be rich in organic matter and nutrients like nitrogen, phosphorus, and potassium. The soil structure should also be loamy, with excellent water retention abilities.
Cultivation Methods
Allium cepa L. var. proliferum, commonly known as tree onion or walking onion, is an easy-to-cultivate perennial plant that requires well-drained soil and a sunny location. They can be grown either from seed or from sets, small bulbs that have been grown for a year.
Plant the sets in spring, placing the pointed end facing up, and cover them with about 1 inch of soil. Space them 6 inches apart in rows that are 12 inches apart. Alternatively, direct sow the seeds in early spring or fall, thinly covering them with soil.
Watering Needs
Water your tree onions evenly throughout the growing season, especially during dry spells or when growing them in containers. The soil should be kept consistently moist but not waterlogged, which can cause root rot. During the winter months, it is recommended to reduce watering and let the soil dry out slightly between waterings.
Fertilization
For optimal growth, apply a balanced fertilizer, like a 10-10-10, at a rate of 1 pound per 100 square feet in early spring. Alternatively, use a slow-release fertilizer in early spring or mulch with well-rotted compost or aged manure. Fertilize again in mid-to-late summer using the same amount of fertilizer.
Pruning
Prune or harvest the leaves when they are about 6 inches long to encourage new growth throughout the season. In late summer or early fall, remove the flowering stalks, which can lead to new bulb growth. After a few years, lift the bulbs in the spring when the foliage dies, separate the clusters, and replant them elsewhere.
Propagation of Allium cepa L. var. proliferum (Moench) Regel
Allium cepa L. var. proliferum (Moench) Regel, commonly known as tree onion or walking onion, can be propagated through various methods.
Bulb Division
The most common method of propagation is by bulb division. It involves separating the bulbs from the mother plant and replanting them. Each bulb should have a growing point or shoot, and a portion of the root system.
Bulb division can be done in spring or fall. After lifting the bulbs, remove any damaged or diseased ones. The bulbs should be gently separated and replanted immediately.
Bulbils
Tree onion plants produce small bulbs called bulbils on the tops of their stalks. These bulbils can be used as a propagation method. Allow the bulbils to mature on the plant until they start to dry out and separate from the stalk.
After harvesting the bulbils, they should be replanted immediately in well-draining soil. Plant them 1-2 inches deep with the pointed end up and the flat base down.
Seed
Allium cepa L. var. proliferum (Moench) Regel can also be propagated by seed. Sow the seeds in early spring or late fall. The seeds should be planted in well-draining soil, 1/4 inch deep and 1-2 inches apart.
Keep the soil moist, but not wet. Germination can take up to three weeks. Once the seedlings grow to 4-6 inches tall, they should be transplanted to their permanent location with a spacing of 6 inches between plants.
Disease Management
Allium cepa L. var. proliferum (Moench) Regel, commonly known as walking onion or Egyptian onion, is a hardy plant that is relatively resistant to diseases. However, some diseases that can affect the plant include:
Basal rot
Basal rot is a fungal disease caused by Fusarium oxysporum that can cause the leaves to yellow and the bulbs to rot. It can be managed by planting disease-free bulbs and avoiding planting in areas where Alliums have been grown recently. Crop rotation can also reduce the incidence of the disease.
Downy mildew
Downy mildew is a fungal disease that can cause the leaves to turn yellow, and a white powdery growth to appear on them. It can be managed by planting resistant varieties of Alliums, and ensuring that there is good air circulation around the plants. Avoid planting in areas that are frequently damp or wet.
Smudge
Smudge is a fungal disease caused by Alternaria porri that can cause dark spots on the leaves. It can be managed by planting disease-resistant varieties, avoiding overhead watering and ensuring good air circulation. Fungicides can also be applied following manufacturer's instructions.
Pest Management
Onion Maggot
The onion maggot is a common pest that can affect the Allium cepa L. var. proliferum. It can cause yellowing and wilting of the leaves. The larvae of the onion maggot feed on the roots, reducing the plant’s ability to absorb nutrients. It can be managed by placing a fine mesh over the plants to prevent the adult flies from laying their eggs near the plants. Crop rotation can also be done to reduce the population of the onion maggots.
Thrips
Thrips are small, slender insects that can cause discoloration of the leaves and flowers of Allium cepa L. var. proliferum. They feed by sucking the sap from the leaves and can be seen walking on them. They can be managed by introducing natural predators like ladybugs or lacewings into the garden. Pesticides can also be used following the manufacturer's instructions.
Armyworms
Armyworms are caterpillars that can cause significant damage to the Allium cepa L. var. proliferum. They can eat the leaves and the flowers, causing significant damage to the plants. It can be managed by introducing natural predators into the garden such as birds, and using pesticides following the manufacturer's instructions.
