Botanical Classification
Kiwifruit, commonly known as kiwi, belongs to the genus Actinidia within the family Actinidiaceae. The primary commercial species are Actinidia deliciosa (green kiwi) and Actinidia chinensis (golden or yellow kiwi), though over 70 species exist in the genus. Originally classified as Actinidia chinensis, the green kiwi was later distinguished as A. deliciosa due to differences in fruit characteristics and chromosome count (A. deliciosa is hexaploid, while A. chinensis is diploid or tetraploid).
These woody, deciduous vines are dioecious, meaning male and female flowers typically grow on separate plants, requiring cross-pollination for fruit production. Mini kiwis, or baby kiwis (e.g., Actinidia arguta), are smaller, fuzz-less varieties gaining popularity for their edible skin.
History
Kiwifruit originated in the Yangtze River Valley of northern China, where it was known as “yang tao” or “Chinese gooseberry” and used for centuries in traditional medicine and as a wild food source. In the early 20th century, seeds were introduced to New Zealand by missionary Mary Isabel Fraser in 1904, leading to its cultivation and renaming as “kiwifruit” in 1959 by exporter Turners & Growers, inspired by New Zealand’s kiwi bird due to the fruit’s fuzzy, brown exterior.
Commercial cultivation began in the 1960s, with New Zealand establishing itself as a global leader, particularly with the ‘Hayward’ cultivar of green kiwi. By the late 20th century, kiwifruit spread to Europe, the United States, and South America, with golden kiwi varieties like ‘Hort16A’ (Zespri Gold) introduced in the 1990s for their sweeter flavor. Today, it’s a major crop worldwide, with Italy, New Zealand, and China as top producers.
Identifying Characteristics
Kiwifruit grows on vigorous, twining vines with large, heart-shaped, dark green leaves that are slightly fuzzy on the underside. The vines produce creamy-white to yellowish flowers in spring, with female flowers developing into oval or oblong fruits, typically 5–8 centimeters long. Green kiwis (A. deliciosa) have a brown, fuzzy, edible skin encasing vibrant green flesh speckled with tiny, edible black seeds arranged in a radial pattern around a creamy white core.
Golden kiwis (A. chinensis) feature thinner, bronze-colored skin with smoother, sweeter, yellow-orange flesh and fewer seeds. Mini kiwis (A. arguta) are grape-sized, with thin, glossy, green or reddish skin and green flesh, requiring no peeling. The fruit’s texture is soft and juicy when ripe, with a distinctive sweet-tart flavor in green varieties and a tropical, mango-like sweetness in golden ones.
Growth Rate and Lifespan
Kiwifruit vines are fast-growing, capable of extending 6–10 feet per year under optimal conditions, which include well-drained, fertile, slightly acidic soil (pH 5.0–6.5) and full sun to partial shade. Vines require sturdy support structures like trellises or pergolas due to their climbing nature. They typically begin fruiting 3–5 years after planting, with peak production at 7–10 years, yielding 50–100 pounds of fruit per vine annually under good management.
With proper care, including pruning and protection from frost, kiwifruit vines can live 30–50 years or more, though commercial orchards often replace them after 20–25 years for optimal yield. Pollination is critical, with one male vine needed for every 6–8 female vines, and bees or wind facilitating the process.
Distribution
Native to East Asia, particularly China, kiwifruit is now cultivated globally in temperate and subtropical regions with mild winters and warm summers. Major producers include China (over 50% of global supply), Italy, New Zealand, Chile, Greece, and France, with smaller but significant production in the United States (primarily California), Australia, and Japan.
Ideal growing conditions are found in regions with 700–800 chilling hours (below 45°F) for dormancy and frost-free springs to protect flowers. The fruit thrives at elevations up to 1,200 meters in areas like New Zealand’s Bay of Plenty, Italy’s Lazio, and China’s Shaanxi province. Wild Actinidia species still grow in Chinese forests, while commercial orchards dominate in regions with suitable climates.
Landscape and Other Uses
Kiwifruit vines are valued in landscaping for their ornamental qualities, with lush foliage and attractive flowers making them ideal for covering pergolas, arbors, or fences in gardens. Their vigorous growth provides shade and aesthetic appeal, particularly in Mediterranean or temperate climates.
Beyond ornamental use, kiwifruit is a culinary staple, eaten fresh, juiced, or used in smoothies, desserts, salads, and salsas. The fruit’s high pectin content makes it excellent for jams, and its enzymes (notably actinidin) are used as a meat tenderizer. In traditional Chinese medicine, kiwi roots and leaves were used to treat joint pain, bleeding, and digestive issues. The vines also support biodiversity by attracting pollinators, though their wood is not commercially significant.
Nutritional Value
Kiwifruit is highly regarded for its exceptional nutritional profile. It is an outstanding source of vitamin C, often surpassing citrus fruits in content, and also provides vitamin K, vitamin E, folate, and dietary fiber. Its antioxidants, including carotenoids and polyphenols, contribute to its health benefits, supporting immune function, cardiovascular health, and digestive wellness. The fruit’s enzyme actinidin aids in protein digestion, making it particularly useful as a natural digestive aid. Low in calories yet nutrient-dense, kiwifruit is considered a superfood and a valuable addition to a balanced diet.
Cultivation of Kiwifruit (Actinidia deliciosa)
Climate Requirements
Kiwifruit thrives in temperate climates with warm summers and mild winters. It requires sufficient winter chilling (between 600–1,000 hours below 7°C) to break dormancy but is sensitive to late spring frosts that can damage young shoots and flowers.
Soil Conditions
The plant prefers deep, fertile, well-drained soils rich in organic matter. Slightly acidic soils (pH 5.5–6.5) are ideal, as alkaline conditions can lead to nutrient deficiencies such as chlorosis.
Site Selection
Vines should be planted in areas sheltered from strong winds and heavy frosts. Slopes or elevated areas are often chosen for better air circulation and drainage, reducing the risk of root rot and frost damage.
Propagation
Kiwifruit is commonly propagated through grafting or cuttings to ensure desirable fruiting traits. Seed propagation is possible but rarely used commercially, as it produces variable plants that may not match the parent variety.
Male and Female Vines
Being dioecious, kiwifruit requires both male and female vines for pollination. Typically, one male vine is planted for every 6–8 female vines. In some orchards, beehives are introduced to improve pollination success.
Planting and Spacing
Plants are spaced about 3–5 meters apart in rows, with row spacing of 4–5 meters to allow machinery and airflow. Proper spacing reduces competition for light and nutrients and helps prevent disease.
Trellising Systems
Because vines are vigorous climbers, strong support systems such as pergolas, arbors, or T-bar trellises are essential. These not only support heavy fruit loads but also improve light penetration and air circulation.
Irrigation
Kiwifruit requires consistent soil moisture, especially during flowering and fruit development. Drip irrigation is often preferred as it conserves water and minimizes leaf wetness, reducing fungal disease risks.
Nutrient Management
Regular fertilization with nitrogen, phosphorus, potassium, and trace elements is necessary to sustain growth and fruiting. Organic compost or mulching improves soil fertility and moisture retention. Leaf analysis is often conducted to guide fertilizer applications.
Pruning
Annual pruning is critical for managing vine shape, controlling vigor, and encouraging fruitful shoots. Winter pruning removes old wood, while summer pruning helps regulate canopy density, light penetration, and air flow.
Pest and Disease Control
Kiwifruit is susceptible to fungal diseases like botrytis, root rot, and bacterial canker (Pseudomonas syringae). Regular monitoring, good orchard hygiene, and preventive sprays help reduce losses. Birds are also a common pest, often requiring netting.
Harvesting
Fruits are usually harvested in late autumn when they reach the desired sugar content (measured in °Brix). Kiwifruit is picked firm and ripens off the vine during storage, which allows long-distance shipping without damage.
Post-Harvest Handling
Proper storage is crucial, as kiwifruit can be kept for several months under controlled conditions (0–1°C with high humidity). Ethylene gas can be used to hasten ripening before market distribution, ensuring optimal sweetness for consumers.