The satsuma (Citrus unshiu) is one of the sweetest and most cold-hardy citrus fruits. Originating in China, the name 'Satsuma' comes from the province in Japan where trees were grown that were first introduced to the West. The fruits were first brought to North America in the 18th century.
With its loose, leathery skin, this is an easy-to-peel fruit, and it has around 12 segments of delicate and juicy flesh. The small to medium-sized trees are low-growing with a spreading and droopy habit. The pretty white blooms appear in spring and are attractive to early pollinators. Grown from seed, it can take up to eight years before you will reap your first harvest. The timing will be significantly decreased when grafted onto other citrus rootstocks. For best results, plant your satsuma tree in early spring.
|Botanical Name||Citrus unshiu|
|Common Name||Satsuma, satsuma mandarin, unshu mikan, cold hardy mandarin|
|Mature Size||Up to 20 ft. tall|
|Sun Exposure||Full sun|
|Soil Type||Rich, moist|
|Soil pH||Acidic, neutral|
|Hardiness Zones||8-11 (USDA)|
How to Plant Satsuma Trees
When plating a satsuma tree, you should wait until the temperature remains consistently above 50 degrees during the day, for at least a week. This helps to ensure cold temperatures will not kill the plant in its vulnerable state and allows the tree to acclimate to mild temperatures before the heat of summer. If a hard frost does occur late in the spring season, cover the young sapling's branches loosely with a blanket to protect it.
Location is also important. Satsumas do not do well when exposed to wind, so in addition to choosing a location with plenty of sun, you will want some shelter provided by a building or a fence.
How to Care for Satsuma Trees
Most fruit trees require full sun conditions, and satsumas are no exception. They should ideally get eight to 10 hours of direct sunlight, especially in spring during blossom and fruit formation.
Citrus trees prefer sandy, loamy soil with a slightly acidic pH. Satsumas are adaptable to different soil conditions such as rocks or clay, but will not tolerate salty soils. The soil must have good drainage.
Satsuma trees need ample water, so plan on consistent and deep watering throughout the growing season. After planting, water every two to three days, and then once every week to ten days thereafter during the growing season. If you are experiencing a dry spell, watering will need to be more frequent to keep the soil moist.
Temperature and Humidity
Although satsumas are more cold-hardy than other citrus trees, they still need consistently warm temperatures during their growing season. Cool winters and hot, humid summers produce the best fruit harvest.
Mature, dormant trees can easily survive in temperatures down to 14 degrees Fahrenheit during the winter. If temperatures dip lower than this, or you have a young tree, implementing some cold protection strategies is recommended. Mounding the base of the trunk with around 2 feet of soil during these times can be beneficial (it should be removed again when the frosts pass). Alternatively, you could invest in a trunk wrap. Winter temperatures between 25 to 35 degrees Fahrenheit are actually said to enhance the sweetness of the fruits.
Satsuma trees benefit from regular fertilizing. It's best to fertilize in late January to early February when the tree is producing new growth. You may use a balanced 8-8-8 citrus fertilizer that contains nitrogen. A two-year-old tree can handle one to one and a half pounds of fertilizer.
There are over 100 satsuma cultivars to choose from. They can vary considerably in terms of when they mature, shape, color, and harvest quantity and quality. Some popular and readily available examples include:
- 'Owari': This productive tree produces high-quality fruit that rarely produces seeds
- 'Brown Select': The tree has a less droopy habit than most and has a dense, compact form. The rind easily separates from the flesh of the acidic, sweet fruit
- 'Silverhill': The shape of the fruit on this tree is flatter than most, and it has a high sugar and low acid content, making it particularly sweet. The tree is known for being vigorous and productive, with a more upright growth habit than most
- 'Early St. Ann': The fruit is ready for harvesting mid-September through October—this is around a month earlier than most other cultivars
Satsumas vs. Mandarins
Under some classification systems, Citrus unshiu is considered a species in its own right. Under others, they are considered to be a group of mandarin varieties. Genetics show the fruit is actually a mandarin-pomelo hybrid.
The satsuma is similar in size to its mandarin (Citrus reticulata) relatives, but it has a softer, more delicate texture and a looser rind, and it is ready to harvest earlier too.
Satsumas are generally able to be harvested between October and December, depending on the cultivar grown. They don't do well hanging on the tree after maturity. Prompt picking when ripe is important, and they can then be stored in a refrigerator with temperatures between 32 and 36 degrees Fahrenheit.
As the fruit reaches maturity, the rind will become looser (separating a bit from the flesh), and the surface will become bumpier. The ripe fruit coloring can vary depending on the climate. In humid regions, the fruit may be ripe even while it is still green, and a reddish-orange hue is possible when night temperatures are cool.
Because the rinds are loose, it is best to clip the fruit from the tree rather than plucking. If you damage the rind when picking, it will lead to fast decay. Of all the citrus fruits, the satsuma is one of the most delicate and care should be taken when handling it.
How to Grow Satsumas in Pots
Although satsuma trees can grow up to 20 feet tall, they can be trained to stay smaller and can be grown in containers. Keeping your mature satsuma pruned to about 5 or 6 feet tall and wide is a good rule of thumb.
The main benefit of planting satsumas in containers is that they can be moved indoors during the fall and winter. Placed near a sunny window and watered regularly (mist the leaves to keep the humidity up, as indoor heating has a drying effect), your satsuma will produce tasty fruit for you during the cold months.
Because satsuma trees have a prostrate growth habit, pruning is essential to prevent fruit on low lying limbs from touching the ground. The best time to prune your tree is early spring after the danger of frost. Prune any branches growing below eighteen inches above the ground. Remove leaf debris from beneath the trees to help keep them clean and disease-free.
You can propagate satsumas from leafy cuttings using rooting talc, but the usual way they are grown is by grafting, as with most fruit trees. The best time to get cuttings is in summer, during active growth. Satsumas grown from cuttings will remain tender and vulnerable for the first two years, so wait before planting them outside. It's important to know that American citrus crops can be susceptible to certain location-specific diseases, and the USDA recommends not moving or transplanting citrus trees from one state to another.
Common Pests and Diseases
Although satsuma trees are hardy compared to some other citrus varieties, they can be prone to a fungal disease called sour orange scab. This causes lesions on leaves, branches and fruit. Thankfully, it doesn't usually affect the quality of the fruit flesh.