Lonicera caerulea

Haskap is a deciduous shrub growing to 1.5–2 m (4 ft 11 in – 6 ft 7 in) tall. The leaves are opposite, oval, 3–8 cm (1.2–3.1 in) long and 1–3 cm (0.39–1.18 in) broad, greyish green, with a slightly waxy texture. The flowers are yellowish-white, 12–16 mm long, with five equal lobes; they are produced in pairs on the shoots. The fruit is an edible, blue berry, somewhat rectangular in shape weighing 1.3 to 2.2 grams (0.046 to 0.078 oz), and about 1 cm (0.39 in) in diameter.[7]

The plant is winter-hardy and can tolerate temperatures below −47 °C (−53 °F).[8] Its flowers are frost-tolerant. Fruits mature early and are high in vitamin C.[9]

Haskap cultivars can survive a large range of soil acidity from 3.9-7.7 (optimum 5.5-6.5), requiring high organic matter, well drained soils, and plentiful sunlight for optimum productivity. Lonicera caerulea plants are more tolerant of wet conditions than most fruit species.[8][10]

The species is circumpolar, primarily found in or near wetlands of boreal forests in heavy peat soils of North America, Europe, and Asia.[6][11] It also can be found in high-calcium soils, in mountains, and along the coasts of northeastern Asia and northwestern North America.[8]

Different varieties are distributed across central and northern Canada, northern United States, northern and eastern Europe, Siberia, middle Asia, and northeastern China.[6]

Haskap berry diversity

Haskap berries and leaves

The classification within the species is not settled. One classification uses nine botanical varieties:[6]

• Lonicera caerulea var. altaica. Northern Asia.
• Lonicera caerulea var. caerulea. Europe.
• Lonicera caerulea var. cauriana. Western North America.
• Lonicera caerulea var. dependens. Central Asia.
• Lonicera caerulea var. edulis, synonym: L. edulis. Eastern Asia.
• Lonicera caerulea var. emphyllocalyx (also known as haskap). Eastern Asia.
• Lonicera caerulea var. kamtschatica. Northeastern Asia.
• Lonicera caerulea var. pallasii. Northern Asia, northeastern Europe.
• Lonicera caerulea var. villosa. Eastern North America.

Haskap products on retail display in a Japanese market

The indigenous peoples of eastern Russia, northern Japan and northern China have long harvested the wild berries, but cultivation efforts are relatively recent, beginning in the Soviet Union in the 1950s. Research into commercial cultivation continued in Hokkaido, Japan in the 1970s. The plant is mostly unknown in the Western world,[9] even while some varieties grow in northern Canada and northern United States. Haskap variety edulis has been used frequently in breeding efforts, but other varieties have been bred with it to increase productivity and flavor. In several haskap breeding programs, the variety emphyllocalyx has been the dominant one used.[8]

Honeysuckle is harvested in late spring or early summer two weeks before strawberries for Russian type varieties, with Japanese types ripening at a similar time to strawberries.[8] The berries are ready to harvest when the inner layer is dark purple or blue. The outer layer is dark blue and looks ripened, but the inner layer may be green with a sour flavor.[8][11] Two compatible varieties are needed for cross pollination and fruit set. In North America, most Russian varieties are adapted to hardiness zones 1 to 4. The plants may take three or four years to produce an abundant harvest.[8] Average production on a good bush is about 3 kilograms (6.6 lb), and bushes can maintain productivity for 30 years.[8]

Honeysuckle can be used in various processed products, such as pastries, jams, juice, ice cream, yogurt, sauces, candies and a wine similar in color and flavor to red grape or cherry wine.[8][11][12]

As a blue pigmented fruit, Lonicera caerulea contains polyphenol compounds, including cyanidin 3-glucoside, cyanidin 3-rutinoside, peonidin 3-glucoside,[13][14] proanthocyanidins and organic acids, including citric acid.[15]

Over centuries in East Asian countries, Lonicera caerulea has been used for supposed therapeutic applications in traditional medicine.[16]