Yuzu (Citrus junos)

With a tart and floral flavor, yuzu fruits provide a uniquely refreshing taste to sauces and marinades. Read on to how to grow this cold-hardy citrus at home.

I. Appearance and Characteristics

Yuzu (Citrus × junos, from Japanese 柚子 or ユズ; ) is a citrus fruit and plant in the family Rutaceae of East Asian origin. Yuzu has been cultivated mainly in East Asia, though it has also recently been grown in New Zealand, Australia, Spain, Italy, and France.

It is believed to have originated in central China as an F1 hybrid of the mangshanyeju subspecies of mandarin orange and the ichang papeda.

This fruit resembles a yellow clementine with uneven skin and can be either yellow or green depending on the degree of ripeness. Yuzu fruits, which are very aromatic, typically range between 5.5 and 7.5 cm (2+1⁄8 and 3 in) in diameter but can be as large as a regular grapefruit (up to 10 cm or 4 in, or larger).

Yuzu forms an upright shrub or small tree, which commonly has many large thorns. Leaves are notable for a large, leaf-like petiole, resembling those of the related makrut lime and ichang papeda, and are heavily scented.

Yuzu closely resembles sudachi (Citrus sudachi, a Japanese citrus from Tokushima Prefecture, a yuzu–mandarin orange cross) in many regards, though, unlike the sudachi, yuzu eventually ripen to an orange colour and there are subtle differences between the flavors of the fruit.

The yuzu originated and grew wild in Tibet and central China. It was introduced to Japan and Korea during the Tang dynasty and is still cultivated there. It grows slowly, generally requiring ten years to fruit. To shorten the duration to fruiting, it may be grafted onto karatachi (P. trifoliata). It is unusual among citrus plants in being relatively frost-hardy, due to its cold-hardy Ichang papeda ancestry, and can be grown in regions with winters as low as −7 °C (19 °F) where more sensitive citrus would not thrive.

II. How to Grow and Care

Sunlight

Yuzu plants like lots of bright light, but they can handle a few hours of shade. Regardless of whether you’re planting your yuzu in the ground or in a container, choose an area that receives at least six hours of direct light each day.

When it comes time to move your plant indoors for the winter, place the pot in a bright room near a south-facing window. If your home resembles a dim dungeon rather than a bright greenhouse, use a grow light to provide supplemental lighting.

Temperature and Humidity

Yuzu plants can tolerate a wide range of temperatures and aren’t very picky about humidity. During the growing season, they prefer temperatures between 50-85°F (10-29°C), but they won’t become stressed by brief periods outside this range.

Most yuzu plants can tolerate temperatures as low as 20°F (-7°C), and some people report their plants have survived temperatures down to 0°F (-18°C).

Watering

Yuzu plants prefer their soil to be slightly moist but can tolerate brief dry spells. The temperature, humidity, and plant size all impact your watering schedule, so there’s no one-size-fits-all prescription for keeping your plant properly hydrated. With that said, a good rule of thumb is to water your yuzu plant deeply once a week from spring through early fall.

Since your plant will be growing more slowly during the winter months, it won’t require as much water as it will in the summer. Plan to water potted indoor yuzu plants once every two weeks during the winter, but be ready to adjust as necessary. Overwatering is a common issue during the winter, so err on the side of underwatering rather than overwatering.

Soil

If you’re growing your yuzu plant in the ground, make sure the soil is well-drained. Loosening the soil with a digging fork and mixing in pine bark or finished compost before planting helps improve drainage.

If you plant your yuzu in a container, choose a coarse, well-draining soil mix with a slightly acidic pH. Avoid mixes designed for seed starting and opt for chunkier mixes with additions of pumice and/or bark. You can design your own yuzu potting mix, but an easy option is to purchase a mix designed for citrus trees.

Fertilizing

Yuzu plants benefit from regular additions of appropriate fertilizer. Choose a citrus fertilizer with close to equal amounts of nitrogen and potassium coupled with half the amount of phosphorus. Some NPK ratios that work well include 6-3-5 and 5-2-5. Fertilizers should also contain the nutrients calcium, sulfur, iron, and zinc.

Follow product instructions and fertilize three times per year: once in late winter, once in mid-spring, and once in mid-summer. Avoid applying fertilizer during the fall since this can encourage the plants to produce new growth that’s extra-susceptible to cold damage.

Planting Instructions

• Planting Yuzu in the ground

Yuzu, like most citrus trees, prefers neutral, slightly acidic, and non-limestone soils. It is only reasonable to plant it in the ground if you reside in the olive tree zone, where temperatures do not drop below -10°C (14°F) for brief periods and rise significantly during the day. Citrus trees are heat and sun-loving bushes. The best time to plant is in early spring, in March and April. Be careful not to bury the collar.

Citrus trees are naturally greedy and require water to bear fruit well: in any case, consider amending with well-decomposed compost or “special citrus” fertilizer. Choose a sunny but not scorching location for your bush, sheltered from the wind to prevent it from drying out the foliage and dropping young forming fruits. Place it in a location protected from sea spray.

• Planting in a pot

In all other regions, Yuzu will be planted in a pot that you can keep in a greenhouse or a minimally heated conservatory, but frost-free permanently but will appreciate being outside in summer. Planting in a pot or repotting takes place at the end of summer.

Choose a pot slightly larger than the root system, citrus trees do not like to feel cramped. Moisten the root ball well. To improve the drainage capacity of the mixture, line the bottom of the pot with clay balls. Loosen the root ball and mix two-thirds garden soil with one-third “special citrus” compost. Water thoroughly. Prefer terracotta pots or breathable materials.

Citrus trees need a lot of water to thrive. Your Yuzu must be regularly watered with water that is low in or free from limestone, and the soil must remain moist at all times. Similarly, make sure to regularly provide it with the fertilizer it needs: every 6 months for slow-release granular fertilizer or every 3 waterings for liquid fertilizer.

Pruning

Your yuzu tree will continue to grow and produce fruit if you forgo pruning, but regular pruning keeps the plant healthy and maintains its shape. Pruning can also help you restore overgrown trees you’ve inherited.

The best time to prune your yuzu plant is the late winter or early spring, just before rapid growth resumes. No matter what type of pruning you complete, use sharp and sanitized pruning shears to make clean cuts and prevent the spread of disease.

When pruning, start by removing any dead or diseased wood. Next, remove any stems growing vertically from the main branches (aka waterspouts) as well as suckers emerging from the base of the plant.

Propagation

Yuzu plants are moderately difficult to propagate at home, but if you’re up for a challenge, you can create new plants to expand your collection or share with friends. The best ways to propagate yuzu are rooting or grafting cuttings. I recommend rooting cuttings since this method is easier to complete at home and doesn’t require a rootstock.

Repotting

If your yuzu is growing in a pot, it will eventually outgrow its container and require repotting. It’s easy to want to bump your plant from a one-gallon to a five-gallon pot, so you only have to repot it once, but this sudden change in container size can lead to excess moisture and associated problems. Instead, bump your plant up into a container that’s only a few inches wider than the original.

To propagate your yuzu by rooting the cuttings, follow these steps.

• Locate a healthy stem that’s about pencil width. Use a sharp and sanitized pair of pruning shears to cut just below a leaf node.
• Trim the cutting to 8-12 inches long, then remove the leaves from the bottom four to six inches of the cutting.
• Dip the bottom of the cutting in a rooting hormone. While this step is optional, it increases the chances that the plant will form roots.
• Place the bottom two to three inches of the cuttings in a container filled with moist coco coir or peat moss, ensuring the container has drainage holes to let excess water escape.
• Cover the cuttings with a plastic dome or bag to trap humidity, but make sure the plastic isn’t touching the top of the plants.
• Place the cuttings somewhere where they receive bright light for at least six hours each day.
• Continue to water the potting material so it stays moist but not saturated.
• The cuttings should form new roots within one month and be ready for repotting within two months.

Common Problems

Yuzu plants rarely succumb to pests or diseases, but they often struggle to remain healthy or produce fruit due to improper care. Here are some of the most common problems to watch out for and how to prevent and treat them.

• No Flowers

A close-up of a yuzu stem, adorned with green leaves that add freshness to the scene. The blurred background gracefully highlights the presence of other tree leaves, creating a harmonious and natural composition.

Remember that yuzu plants are slow-growing, so they won’t produce flowers during their first few years of growth. Multiple factors could be to blame if your plant is mature but still not producing any flowers.

First, check to see that your plant is receiving enough light. Flower production is an energy-intensive process, so plants are unlikely to produce blooms if they don’t receive enough sunlight. Ensure your plants receive at least six hours of direct light each day, and supplement with a grow light when necessary.

If your plant is producing lots of healthy green growth but no flowers, check your fertilization routine. Too much nitrogen will cause plants to produce plenty of vegetative growth but no flowers. Remember to choose a fertilizer with similar amounts of nitrogen and potassium, and only fertilize your yuzu a few times per year.

• Yellow Leaves

Yuzu leaf yellowing may stem from factors like temperature stress.
There are many reasons why your yuzu leaves are changing from vibrant green to yellow, but they all relate to stress. Improper temperature, lack of nutrients, too much water, too little water…the list of possibilities goes on. With so many possible causes of yellow leaves, the best way to determine the cause is to examine your care routine.

Is the soil staying wet between waterings? Overwatering or root rot are likely to blame.

Forget to fertilize your plant for the past year? It’s probably lacking one or more essential nutrients.

Did you just move your potted yuzu from a cozy indoor room to the outdoors? Your plant is likely recovering from the stress accompanying this environmental change.

After you find out what care factor is awry, you can take steps to provide the proper care and help your leaves return to green.

• Brown Leaf Tips

While it can be difficult to pinpoint the cause of yellow leaves, it’s a bit easier to identify the reason behind brown leaf tips. If you see the tips of the leaves transforming from lush green to crispy brown, salt buildup is the most likely cause. This often results due to over-fertilization, but it can also appear if you’re watering your plant with mineral-rich water.

The best way to remedy this issue is to thoroughly water your plant to flush out excess salts. If you suspect your tap water is rich in salts, use rainwater or filtered water to flush and water your yuzu.

Citrus canker is a disease that can cause browning of leaves and stems. It’s a symptom of fungal infection related to citrus leaf miners and pruning wounds. These cankers are oozing wounds that may be accompanied by fungal growth. The best way to control the issue is to remove any leaves that exhibit damage from leaf miners. Proper care is the most effective means of prevention, and so is proper and careful pruning.

• Sap-Sucking Pests

While natural predators like ladybugs, parasitic wasps, and green lacewings keep pests like aphids and thrips under control outdoors, these tiny critters sometimes become a problem on indoor yuzu.

A few of these pests aren’t a problem, but they can quickly multiply and take over your plant. When this happens, they suck the sap out of the leaves, causing discoloration and even leaf drop.

If you spot aphids, spider mites, thrips, or another type of tiny sap-sucking pest on your yuzu plant, remove the pests ASAP. One way to remove the pests is to wipe them off with a wet, soapy rag. You can also spray larger infestations with neem oil or insecticidal soap.

Citrus psyllids tend to be an issue for all citrus trees. These are small moths that feed on these plants, causing twisting leaves and distorted new leaves. They nest in leaf litter from citrus trees. Most of the time, purchasing a tree from a reputable seller will prevent their infestations. If you notice them, contact your local extension office. They may recommend quarantine or disposal.

III. Uses and Benefits

Culinary uses

• Japan

Yuzu’s domestic production is about 27,000 tons (2016). Though rarely eaten as a fruit, yuzu is a common ingredient in Japanese cuisine, where the aromatic zest (outer rind) and the juice are used much in the same way that lemons are used in other cuisines. The yuzu’s flavor is tart and fragrant, closely resembling that of the grapefruit, with overtones of mandarin orange.

It is an integral ingredient (along with sudachi, daidai, and other similar citrus fruits) in the citrus-based sauce ponzu, and yuzu vinegar is also produced. Yuzu is often combined with honey to make yuzu hachimitsu (柚子蜂蜜), a kind of syrup that is used to make yuzu tea (柚子茶), or as an ingredient in alcoholic drinks such as the yuzu sour (柚子サワー). Yuzu kosho (also yuzukosho, literally “yuzu and pepper”) is a spicy Japanese sauce made from green or yellow yuzu zest, green or red chili peppers, and salt.

It is used to make liquor (such as yuzukomachi, 柚子小町) and wine. Slivered yuzu rind is used to garnish a savory, salty egg-pudding dish called chawanmushi, as well as miso soup. It is often used along with sudachi and kabosu. Yuzu is used to make various sweets, including marmalade and cake. It is used extensively in the flavoring of many snack products, such as Doritos.

• Korea

In Korean cuisine, yuja is most commonly used to make yuja-cheong (유자청, yuja marmalade) and yuja tea. Yuja-cheong can be made by sugaring peeled, depulped, and thinly sliced yuja, and yuja-cha, yuja tea, can be made by mixing hot water with yuja-cheong. Yuja-hwachae (유자화채, yuja punch), a variety of hwachae (fruit punch), is another common dessert made with yuja. Yuja is also a common ingredient in Korean-style Western food, such as salads.

Other uses

Yuzu is also known for its characteristically strong aroma, and the oil from its skin is marketed as a fragrance. In Japan, bathing with yuzu on Tōji, the winter solstice, is a custom that dates to at least the early 18th century. Whole yuzu fruits are floated in the hot water of the bath, sometimes enclosed in a cloth bag, releasing their aroma. The fruit may also be cut in half, allowing the citrus juice to mingle with the bathwater. The yuzu bath, known commonly as yuzu yu (柚子湯), but also as yuzu buro (柚子風呂), is said to guard against colds, treat the roughness of skin, warm the body, and relax the mind.

Use as wood

The body of the taepyeongso, a Korean traditional oboe, close to the Chinese suona or the zurna, is often made from jujube, mulberry, or yuzu wood.

IV. Harvesting and Storage

These fruits are typically fully ripe in the late fall or early winter. You’ll know fruits are ready to harvest when they change from light green to yellow or light orange. If the fruits feel soft to the touch, they’re overripe.

After you harvest yuzu fruits, store them in the refrigerator and enjoy them within a month. Remember that yuzu is tart, so you probably don’t want to slice it up for a snack. However, the tart juice and flavorful rind work great in drinks, marinades, and marmalades.