Last Updated on November 14, 2022 by Plant Mom Care
Mandarin orange tree (Citrus reticulata) produces very sweet fruit and is indigenous to the Philippines and Southeast Asia. They are more cold-tolerant than other citrus varieties.
The dark green leaves are ovate or lanceolate and have thorns in their axils. The small five-petaled flowers are white and form clusters. The fruit is much smaller than typical oranges and starts as green, then turns orange when ripe.
The tree is self-fertile and produces seedless fruit if not pollinated. Commercial growers often cover the trees with special netting to stop insects from pollinating the flowers, although some seedless varieties do not require netting.
Standard mandarin trees grow to around 25 feet high when mature while semi-dwarfs grow around 8-10 feet. The tree starts flowering in spring forms fruit in summer, and is ready for harvest in late autumn or early winter. They are not deciduous although growth slows down in winter.
The best time for planting trees is from April to August. Don’t plant when temperatures rise above 100°F. Plant them in a sunlit area in well-drained soil. Semi-dwarf trees can also be kept in large containers. These trees require some care and attention as they need pruning and fertilizing every year and must be closely observed for pests or diseases.
Mandarin Orange Tree Light Requirements
These trees can grow under full or partial sun, needing 8 – 12 hours of sunlight every day to flourish. Young foliage can suffer from sunburn on very hot days although the damage is slight – this can be avoided by covering the trees with a shade cloth.
Dwarf trees grown indoors should be placed near a south/west-facing window. Supplemental growth lights will help the trees produce fruit better, particularly if the light is insufficient.
Mandarin Orange Tree Watering
Water the tree once weekly (early morning). Soil should be moist, but not saturated or water-logged. Avoid wetting the tree trunk to prevent fungal problems. Potted trees need more frequent watering. The soil should be fully saturated and left to dry down before watering it again.
Trees should be watered well when fruits are forming. Once they reach full size, reduce the water to allow them to increase their sugar content.
Mandarin Orange Tree Humidity
They need higher humidity levels of around 50% or more to flourish and produce fruit. Trees living in low humidity will start wilting and brown edges will appear on the leaves. In addition, flower buds will not develop properly or may shrivel or drop off.
Indoor environments usually have low humidity and this can be supplemented by placing a humidifier near the tree or by surrounding the tree with other plants and misting the foliage regularly.
Mandarin Orange Tree Temperature
They prefer temperatures about 40 – 90°F while the temperature should not drop below 55°F. They can tolerate low temperatures around 20°F for a little while or temperatures over 100°F if they get enough water. Temperatures below 55°F will make them dormant and extended lows below 55°F could kill them. Freezing temperatures will damage the fruit. They are cold-hardy in zones 8 – 11.
Mandarin Orange Tree Soil
These trees can tolerate a broad variety of soil types as long as they have good drainage. Adding vermiculite or perlite will help water drainage. They thrive in pH levels of 5.5 – 6.2.
Mandarin Orange Tree Repotting
These trees must be repotted in spring before they start actively growing. Potted trees need repotting around every 3 or 4 years if overall growth slows down or if the roots begin growing out from the drain holes. Repotting helps renew nutrients for good foliar growth and fruit production.
Use a pot about 25% larger than the existing one with good drainage capacity. Place broken pot pieces or stones inside the pot to aid drainage.
Next, add a layer of suitable potting mix, after taking the plant from the previous container, put it in the new one and cover the roots with more potting soil. Water thoroughly and keep the tree under partial shade for some time to let new roots grow.
Mandarin Orange Tree Propagation
Methods of propagating these trees include grafting, cuttings, and air-layering.
Grafting is commonly used by horticulturists as a reliable method to produce strong disease-resistant trees.
Propagation from cuttings
Collect several cuttings – they should be as thick as a pencil and about 12 inches long. Remove any leaves and scrape the bark at the bottom to encourage root growth. You can use rooting hormone or cinnamon powder to help the rooting process and prevent rotting or fungal growth.
Place the cuttings in moist coco peat as it can retain moisture well, making sure the cutting is placed lower end down.
Keep the peat damp but not water-logged. Keep it under indirect light and create mini-greenhouses by covering the cuttings with plastic bags to boost humidity. It can take 3-4 weeks for roots to form and the cuttings can be transferred into your garden or containers after this.
Propagation by air layering
Similar to cuttings, air layering involves having roots form on the branch before being cut off the parent tree. Select a healthy branch as thick as your finger – anything thicker will struggle to adapt once it’s removed from the tree.
Score the bark all around, about 2 – 3 inches long to expose the cambium (inner bark) using a sterile knife. This activates the plant cells and encourages rooting and healing. Wrap the exposed area with sphagnum moss or coco peat.
You can add rooting powder to the moss or peat to help the rooting process. Wrap the media with plastic film to hold it together and tape both ends. Rooting will take about 2 – 4 weeks. Snip the branch off under the new roots, remove the tape, and plastic film and plant the new tree in the garden or container after this. Make sure to water it adequately for its roots to adjust.
Mandarin Orange Tree Additional Care
Fertilize the tree with a citrus-specific formula and follow the instructions so you don’t over-feed the tree. The trees must be well-fed from March to August when they are actively growing and setting flowers and fruit. If a citrus mix isn’t available, use a 12-6-6 blend.
Prune the tree preferably after harvesting fruit in winter or early spring before flowers appear. Remove damaged or dead branches and remove suckers around the tree’s base. Open the canopy to increase air circulation by removing overlapping limbs.
When removing damaged or dead branches, cut back several inches under the damaged or dead branch to remove the entire damaged or dead portion. Clean up any plant debris around the tree to prevent diseases or pests.
Mandarin Orange Tree Common Problems
Mites, thrips, scales, and aphids are insect pests that attack and feed on flowers and foliage. Heavy infestation can stunt growth and cause leaf drop. Aphids also secrete honeydew that attracts mold. Use neem oil and/or insecticidal soap to control infestations.
Phytophthora root rot can cause trees to decline and commonly affects mandarin trees. The leaves can turn yellow or light green. Advanced stages cause sap to ooze from the tree trunk. This disease can be prevented by correct watering practices and well-draining soil.
Botrytis and Anthracnose are foliar diseases and thrive in very wet conditions. Symptoms for both diseases are leaf drop, branch dieback, and fruit decay. Botrytis spores are light gray while Anthracnose spores are dark.
Pruning trees promotes good airflow and prevents excess moisture that attracts both diseases. Removing plant debris will stop these diseases from coming back in the following season.
How long does a mandarin tree take to bear fruit?
Mandarin trees start to produce substantial fruits around 3 – 5 years however, trees propagated from seeds take around 7 years before bearing fruit.
Why is my mandarin tree not fruiting?
This can either be caused by climatic or environmental factors, such as cold temperatures or drought and unreliable watering, particularly during the growing season. Water-established trees once a week in summer.
When should mandarin trees be pruned?
Pruning is best done soon after harvesting fruit in winter or early spring before flowers break out. The benefits from pruning might be delayed or reduced if trees aren’t pruned the correct way at the correct time.
Do mandarin trees produce fruit regularly every year?
Mandarins are well-known for fruiting once in two years. Environmental and climate can also play a role in preventing the tree from fruiting every year. Other factors that prevent regular fruiting could be inconsistent watering, feeding, and improper pruning.