Hovenia dulcis (Japanese Raisin) is a cold hardy tree found that is native to from Korea to the Himalayas. The edible fruit of the Japanese Raisin tree is a substitute for honey in some countries. It is also used in teas, in a variety of traditional medicines and the wood in construction and furniture. The fruit is sweet and fragrant with a taste similar to pears.
Suitable for Cold, Temperate, Dry and Sub-Tropical climates.
The fruit of a Japanese Raisin tree is not a fruit but is actually a swollen receptacle. It is also commonly known as an Oriental Raisin Tree, Kenpo Nashi or Honey Tree. The trees are deciduous and tolerant of temperatures as low as -15°C / 5°F.
Growth
Hovenia dulcis is a a deciduous, edible tree that rarely reaches heights of up to 30 metres (95 feet) and more commonly peaks at 10 metres (33 feet). Japanese Raisin trees seedlings achieve an average growth rate of around 60 cm (2 feet) per year and slow down with age. Seeds can be challenging to germinate. They have an extremely hard black coating which often, in the wild, needs a year or two to wear down. Germination percentage rates when sown without treatment average between 2-5%. Please read instructions in the tab thoroughly before purchasing.
Leaves of Japanese Raisin trees reach up to 15 cm (6 inches) long. Often appearing limp and require rolling out to achieve the maximum length. Trees are drought tolerant though regular moisture during summer improves flowering. From around the age of 5 to 7 years, flowering occurs during Summer where the tree bears clusters of small cream coloured flowers.
The fruits are not exactly fruits. They are edible raisins. After pollination the flowers become swollen and produce an inedible seed pod. As the pod matures, the peduncle of stem attaching it to the cluster swells, becomes knobby and turns a translucent reddish brown. Although the actual size of the fruit is quite small, about the size of a raisin, the trees produce plenty in the right conditions.
FAMILY:
Rhamnaceae
CLIMATE:
Cold, Temperate, Dry and Sub-Tropical.
TEMPERATURE RANGE:
-15°C to 30°C / 5 to 86°F
SOIL TYPE:
Most soil types are ok.
LOCATION:
Full Sun
HEIGHT:
Up to 10 metres (33 feet)
WIDTH:
Up to 7 metres (23 feet)
pH:
6.0-7.0
GROWTH TYPE:
Deciduous
WATER REQUIREMENTS:
Low
POLLINATION:
Self-pollinating.
MATURITY:
5-8 years.
GERMINATION RATES:
5-40%
GERMINATION TIME:
3-4 weeks
SEEDS PER GRAM:
Approximately 50
MEDICINAL QUALITIES:
Yes, Folklore.
WEED POTENTIAL:
No
EDIBLE:
Yes
SEED STORAGE & VIABILITY:
Cold Storage at 4°C (Fridge) up to 4 years.
FACTS ABOUT HOVENIA DULCIS (Japanese Raisin)
Tree grows at roughly the same rate as eucalyptus, reaching six metres in height within three years.
The Japanese Raisin Tree has been used in traditional Japanese, Chinese and Korean medicines to treat fevers, infections and a treatment of liver diseases and as a hangover treatment.
Germination Instructions
HOW TO GROW HOVENIA DULCIS (Japanese Raisin)
Note: There are many tested methods for germinating Japanese Raisin trees as they often have a poor germination rate or are extremely stubborn for water to penetrate. Here are two starting methods. One that is easier, cheaper and requires more patience but averages a strike rate of around 5-10%. And the second requires more experience and additional expense, but averages around 20-40%.
Step 1
For both methods, the first step is to scarify or scratch the seeds to weaken the outer coating. This can be done easily by rubbing the seeds with sandpaper or scratching them against a rough surface such a concrete.
Step 2 – Method 1
Place the scarified seeds in a bowl and pour hot (not boiling) water over the seeds. For those seeking exact temperatures, 60°C / 140°F is the reported number. However, leaving the kettle stand for ten minutes after boiling is generally sufficient. After pouring, leave for 24 hours and repeat the process once more.
From here it is possible to sow the seeds and achieve germination but it can take 4 weeks to find out and some seeds might not germinate for up to a year. We suggest now placing the seeds back into the plastic zip-lock bag. Then adding some moist soil, enough to cover the seeds but not too much as to lose them in it. And placing the bag into the fridge for around 4 weeks. After two weeks, return to lightly mist to keep the soil moist.
After four weeks, separate the seeds from the soil and move onto Step 3.
Step 2 – Method 2
Place the scarified seeds in a bowl. Best to put some plastic gloves on prior to the next step. In a separate jug or container, make a mix of half Sulfuric Acid half Water that is no more than 50-100ml. Stir well and then add the mix into the bowl with the seeds. Let stand for between 120-150 minutes.
Then drain the mix out of the bowl and wash the seeds thoroughly using a strainer and then move onto Step 3.
Step 3
Sow each seed about 2mm deep into small pots of a quality seed-raising mix. Moisten well, cover with plastic and then move the pots into a position where they will receive direct sunlight, at least a few hours per day.
Seeds should germinate in 3-4 weeks but have been known to take 6-12 months depending on soil temperatures which are ideal when kept between 12-20°C / 53-68°F.
Japanese Raisin trees have notoriously low germination rates with rates of between 5-40%.
Step 4
Once sprouted, remove the plastic and move pot/s to a sunny position as long as all frost has passed.
Transplant seedlings from their pots (or upgrade pots if necessary) after their first full winter. Be sure to protect the young seedling from hot sun with some shade or cold winters with some mulching. The eventual final position should be in full sun and in the ground where they can develop deep strong roots.
Once established, Japanese Raisin trees will survive severe cold temperatures and not require much watering unless flowering or fruiting. Maturity in the form of flowers and fruit can take between 5-8 years from seed.
