Common Name: Raisin Tree, Japanese Raisin Tree, Oriental Raisin Tree
Scientific Name: Hovenia dulcis
Family: Rhamnaceae (the Buckthorn family)

The Japanese Rasin Tree has edible fruit stalks, not fruit!

The Raisin Tree has edible fruit stalks, not fruit!

Description:
The Raisin Tree is a unique plant. The edible portion of the tree is not actually the fruit. The fruit itself is small, hard, pea-sized, and not edible. But the stem or stalk of the fruit, once the fruit is mature, will swell up and become gnarled. It is this fruit stalk, technically called a rachis, that is edible. I rarely write about fruits I have not eaten, but this one is so cool that I couldn’t pass it up.

The Raisin Tree is a medium to large tree that is cold tolerant, likes long, hot Summers, can grow in the sun or shade, has edible parts, has a high-quality wood that is used in construction, furniture, tools, and crafts, and has no common pests or diseases. There has been almost no development with this plant, and I think there is a lot of room for improvement… from larger fruit stalks to more cold tolerance to experiments with animal feeding. There is a lot of room to grow with this tree!

The Raisin Tree (Holvenia dulcis)

The Raisin Tree (Holvenia dulcis), Flora Japonica, Sectio Prima (Tafelband), 1870.

History:
Native to the moist, shady mountains of China. Likely brought to Korea and Japan thousands of years ago. Once source states that it was brought to the West in 1820, but it remains a very rare tree here. Another report states that this plant was never cultivated much in Asia for food, but the fruit stalks were collected by children from the wild and used by the family. It has been commercially raised for its high-quality wood.

Trivia:

  • The Japanese name for the edible fruit stalk is kenpo-nashi. My Japanese is not very good, but as best as I can tell, kenpo has a meaning related to the hand or fist. Nashi means pear.
  • The Chinese name for the edible fruit stalk is chi-chao li or chih-chu li which means chicken-claw pear.
  • There is some research being done on the compounds found in the Japanese Raisin Tree. It is hypothesized that these extracts may help prevent liver damage after alcohol intoxication. Some are looking to use it as an “anti-hangover” medicine.

 

The Raisin Tree is a pretty, but subtle tree.

The Raisin Tree is a pretty, but subtle tree.

Although it becomes much more pretty when flowering.

Although it becomes much more pretty when flowering.

USING THIS PLANT

Primary Uses:

  • Edible Fruit Stalk – Can be eaten raw or cooked. Reported to have a flavor similar to Asian Pears or candied Walnuts. The fruit stalks can be dried and then have a flavor and texture more like a raisin. (here is a fun article about cooking with the Raisin Tree)
  • Extract – An extract from the fruit stalks and other parts (young leaves and small branches?) is made in China. It is called “tree honey” and is used as a honey substitute. It is used for making sweets and even a type of wine!

Secondary Uses:

  • Wood is used for construction, flooring, furniture, tools, utensils, artwork, etc.
  • Although I can find no reports of this, the Raisin Tree can likely be coppiced. There is a report that a specimen tree in the Morris Arboretum, Philadelphia, Pennsylvania had a height of 30 feet (9 meters). In the Winter of 1933-34, the record cold froze the tree to the ground. However, “vigorous shoots” grew from the main trunk. Within 8 years, it was back to its 30+ foot height again, and within 45 years (this was a 1978 report), the tree was 78 feet (23 meters)!
  • Wildlife food for both birds and small mammals.
  • Although I can find no reports of this, I would think that the profuse, fragrant flowers would benefit insects, including bees.
  • Drought Tolerant Plant – I have found a few reports that this tree is drought tolerant once established.
  • The Raisin Tree is being evaluated as a reforestation tree. It grows fast enough, attracts wildlife, and is not considered invasive.
  • Medicinal – There is some research to support that the antioxidants in this plant (hodulcine, ampelopsin, quercetin) has liver protecting and anti-inflammatory effects.

Yield: Variable, but one report states that mature trees can yield 5-10 pounds of edible fruit stalks.
Harvesting: The most common complaint I have seen about the Raisin Tree pertains to the harvesting. As this tree can get quite large, trying to harvest the edible fruit stalks from at the very tips of the branches can be difficult. Author Lee Reich suggests cutting off branches and harvesting the fruit stalks from the ground.
Storage: Up to 2 months in a dry, well aerated position. The flavors seem to improve with age… up to a point!

The flowers are small, but numerous and fragrant.

The flowers are small, but numerous and fragrant.

The fruit that develop are only about the size of a pea.

The fruit which develop are only about the size of a pea.

As the fruit matures, the fruit stalk starts to swell and twist.

As the fruit matures, the fruit stalk starts to swell and twist.

Eventually the fruit (at the tips) are mature and dried. They often rattle with the few seeds contained within. But the stalks are swollen and sweet.

Eventually the fruit (at the tips) are mature and dried. They often rattle with the few seeds contained within. But the stalks are swollen and sweet.

These fruit stalks can be eaten fresh - used like you would dried fruit.

These fruit stalks can be eaten fresh – used like you would dried fruit.

...or they can be dried and used like raisins.

…or they can be dried and used like raisins.

DESIGNING WITH THIS PLANT

USDA Hardiness Zone: Zone 5-10. This may vary depending on the origination of the mother plant that the seeds were collected from (i.e. if the mother plant grows in a colder climate, then the seeds may yield trees that are able to tolerate similarly cold climates). It may be worth tracking down seeds/seedlings originating in a climate similar to where you will be planting your trees. Also, there is a good chance that colder specimens can be developed/found with the planting of enough seeds.
AHS Heat Zone: 8-4
Chill Requirement: Likely considering where this plant originates, but no reliable information is available.

Plant Type: Medium to Large Tree
Leaf Type: Deciduous
Forest Garden Use: Canopy Layer, Sub-Canopy Layer
Cultivars/Varieties: Only the single species exists. There are no “improved” varieties.

Pollination: Self-fertile
Flowering: Early Summer. Flowers are small but very numerous

Life Span:

  • Years to Begin Fruiting: 7-10 years, although 3 years has been reported in “ideal” growing conditions (fertile, moist soils and long, warm/hot Summers).
  • Years of Useful Life: 50-150 years, although I found only one source for this information. I honestly do not think there is good information for this.
Leaves of the Raisin Tree.

Leaves of the Raisin Tree.

PHYSICAL CHARACTERISTICS OF THIS PLANT

Size: 30-70 feet (9-21 meters) tall and 20 -40 feet (3-7 meters) wide; however, Raisin Trees typically stay toward the smaller end of their potential.
Roots: No information can be found describing the root system, although I came across many reports that state the roots are not a problem at the surface. This indicates to me that the roots are deeper in nature. This is also supported by the reports that this tree may be drought-tolerant once established.
Growth Rate: Medium

Bark of the Raisin Tree

Bark of the Raisin Tree

The Raisin Tree has high-quality wood.

The Raisin Tree has high-quality wood.

GROWING CONDITIONS FOR THIS PLANT

Light: Full sun to partial shade
Shade: Tolerates light to medium shade, but fruits earlier and in larger quantity in full sun.
Moisture: Prefers moist, but not wet, soils.
pH: One source states 6.1-8.5 and another states “highly acid to slightly alkaline” soils. The reality is that this plant likely tolerates a wide range of soil conditions.

Special Considerations for Growing:

  • Avoid wet soils.
  • Raisin Trees need Summers that hot enough and start early enough (and are therefore long enough) to allow the fruit to ripen. The fruit must ripen enough before the fruit stalk will swell and become sweet.

Propagation:
Typically from seed since no improved varieties exist. Seeds need to be scarified or stratified. Scarification with acid (sulfuric acid for 2 hours) seems to yield the best germination rates. This mimics the degrading process of the hard seed coat which would occur in nature over a very long period of time. Germination can take place within a few weeks but can take up to a few months. Softwood and root cuttings are also proven means of propagation.

Maintenance:
None. It is said that this tree will “self prune”, dropping the lower branches as it grows.

Concerns:
None!

 

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Photo References:

  • http://plantes-du-japon.fr/IMG/jpg/A5B1A5F3A5DDA5CAA5B7A1A1C3E6C9F4.jpg
  • http://images.mobot.org/tropicosdetailimages/Tropicos/275/16902A92-7893-4DC2-BA5F-69BA3ACCAAFF.jpg
  • http://www.tropicos.org/Image/83303
  • http://upload.wikimedia.org/wikipedia/commons/1/1c/Hovenia_dulcis_in_Ceret_Park_São_Paulo_001.jpg
  • http://upload.wikimedia.org/wikipedia/commons/4/48/Hovenia_dulcis.jpg
  • http://coletivocurare.files.wordpress.com/2012/07/hovenia-dulcis22827.jpg
  • http://www.fruitipedia.com/Images%202/Japanese%20raisin%20fruit.jpg
  • http://dbiodbs1.univ.trieste.it/quint/carso/foto/TSB56916.jpg
  • http://dbiodbs1.univ.trieste.it/quint/carso/foto/TSB77800.jpg
  • http://dbiodbs1.univ.trieste.it/quint/carso/foto/TSB77805.jpg
  • http://www.fruitipedia.com/Images%202/Japanese%20raisin%20leaves.jpg
  • http://dbiodbs1.univ.trieste.it/quint/carso/foto/TSB80809.jpg
  • http://4.bp.blogspot.com/-3SVrGhf7IOU/T7diYPk3z-I/AAAAAAAAAKA/WQ6sCqHtEv4/s1600/DSCF5562.JPG
  • http://i01.i.aliimg.com/img/pb/867/678/475/475678867_694.jpg
  • http://dbiodbs1.univ.trieste.it/quint/carso/foto/TSB79640.jpg
  • http://upload.wikimedia.org/wikipedia/commons/b/bb/Hovenia_dulcis_SZ73.png