Thorny olive (Elaeagnus pungens) is a flowering shrub native to Asia. Thorny olive is also commonly called silverthorn. In the United States, thorny olive is planted ornamentally in landscaping in the southeastern region. Thorny olive grows in variable temperate conditions, and it attracts birds.
I. Appearance and Characteristics
Elaeagnus pungens is a species of flowering plant in the family Elaeagnaceae, known by the common names thorny olive, spiny oleaster and silverthorn; also by the family name “oleaster”. It is native to Asia, including China and Japan. It is present in the southeastern United States as an introduced species, a common landscaping and ornamental plant, and sometimes an invasive species.
Elaeagnus pungens is a dense, branching shrub which can reach over 7 meters (23 ft) tall by 4 meters (13 ft) wide. It sprouts prolifically from its stem, spreading out and twining into adjacent vegetation. Parts of the stem are covered in thorns which can be up to 8 centimeters (3.1 in) long. The evergreen, alternately-arranged leaves are up to 10 centimeters (3.9 in) long but under 5 centimeters (2.0 in) wide. The undersides are silvery white with brown flecks.
Tubular flowers are borne in clusters of up to three. The flowers are yellowish or white and are sweet-scented. The fruit is a drupe up to 1.5 centimeters (0.59 in) long which contains one seed. It is reddish with silver scales. Blooming occurs in the autumn and fruit develops during the spring. The plant grows quickly, with shoots growing over one meter per season. The growth has been described as “aggressive”, with shoots extending many meters into neighboring treetops. The seeds are dispersed by birds.
Despite its invasive potential, E. pungens is widely cultivated as a garden plant in temperate regions. It tolerates varied environmental conditions, including heat, cold, wind, coastal conditions, shade, and full sun. It is very drought-tolerant. It can grow in varied soil types, including those found at mine spoils. Numerous cultivars have been developed, especially for variegated foliage effects. Commercially available cultivars include ‘Maculata’, which has gold coloration on the leaves, as well as ‘Fruitlandii’, ‘Hosoba-Fukurin’ and ‘Goldrim’.
II. How to Grow and Care
Sunlight
Thorny olive shrub likes sufficient sunlight, but can also grow in slightly shady environments. It grows best in an open space with over 3 hours of sunlight daily. If light conditions are poor, it won’t grow healthily. Shade it from direct sunlight in hot summers to avoid withering from the blazing sun.
Temperature
plants of the Elaeagnus genus are distributed throughout temperate and subtropical zones. They like warm, moist environments and can tolerate temperatures down to -23 to 2 ℃. Mature thorny olive has strong heat-tolerant and drought-enduring capabilities and only needs watering in dry, hot summers.
Watering
In the first year after planting, thorny olive seedlings need sufficient water. Water infiltrates down in well-drained soil and helps the seedling roots develop downwards. Usually, watering once a week in the spring and summer can keep 30 cm-deep soil moist. Watering can stop in the fall when the seedling moves into dormancy. Mature thorny olive is drought-resistant and only needs watering in dry, hot summers.
Soil
Thorny olive shrub is highly adaptable to soil, and can survive and grow in various soil types. It grows healthily in slightly acidic to alkaline soils, with the most proper pH value being between 6.0-7.5. It can adapt to drought and saline-alkali soil, but cannot tolerate waterlogging. The soil should have good drainage.
Fertilizing
A garden-planted thorny olive shrub doesn’t require much fertilizing. Excessive fertilizing may even make the plant vulnerable to pests and diseases. In the winter, apply a small amount of compost organic manure, or slow-release shrub plant food, as instructed. Nutrients are often scarce in a pot, so apply a thin layer of organic fertilizers once every other month in the spring and PK fertilizer once in the fall to potted thorny olive.
Planting Instructions
When planting in the garden, choose a sufficiently sun-lit, elevated spot. Before planting, clean the soil thoroughly and remove the bigger rocks from the soil. Thorny olive shrub likes soil with good water drainage. If the drainage capacity is poor, it may help to mix fine sand into the soil. The depth of the planting pit should be the same as the height, and twice as wide, as the root ball. The soil surface should be level with the root collar (the juncture of the plant’s trunk and root system). After planting, water sufficiently and cover the soil with 5 to 8 cm-thick organic mulch.
If thorny olive is to be planted in a pot, choose a big pot with good air permeability and drainage holes no less than 25 cm in diameter, so the root system has enough growing space. It may help to lay some bone meal on the bottom of the pot (don’t mix with soil) and mix 1/5 perlite in the soil to increase drainage. After planting, add a 1 cm-thick layer of peat soil on top of the soil surface to help the soil keep moist.
Pruning
Prune for shape in the spring and summer. Winter is the time to prune old, dried branches or trim poorly-growing plants to half of their original height, which helps promote the sprout of robust new branches the next spring. To prevent pests and diseases from invading the branch incisions through rainwater, don’t prune on rainy days. Thorny olive branches are thorny, so wear thick gloves during pruning.
Propagation
Thorny olive shrub can propagate via semi-ripe cuttings, which usually takes place in the summer. Water the plant the night before you select the branches, pick robust new branches the next morning, and cut off 20 cm of them with a pair of sterilized gardening scissors. If there are flower buds on the branches, remove them all. If cottage is not scheduled for that day, the branches can be wrapped in a wet towel and kept in the refrigerator.
On the day of cuttage, trim the length of the branches to 12 to 15 cm. Make sure the incisions are inclined, flat, and smooth, and apply a little rooting powder to them. The leaves and buds on the lower half of the branches should all be removed, and cut each remaining leaf on the upper halves in half. Mix sterilized peat and perlite at 1:1 ratio and place in a pot. Insert the branches 5 to 7 cm deep into the pot and keep them 20 cm apart from each other. Place the pot away from direct light and wind, and put transparent plastic film over the branches. Keep the soil moist, not waterlogged, and transplant after roots sprout.
Transplanting
The ideal season for transplanting thorny olive is during the refreshing transition from late winter to early spring or in the cozy late fall months. Choose a sunny or partially shady location for the best conditions, and remember to be gentle when handling these delicate roots.
III. Uses and Benefits
Thorny olive is a popular evergreen shrub prized for its dense foliage and red berries. It is commonly used as part of a hedge or a focal point in a large garden. It is an essential part of mixed hedge gardens. Plant it with holly or boxwood to add different textures.
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