The Kiwi
The kiwi is a sweet and tangy table fruit.¹ It is about the size of an egg, with green flesh and an iconic fuzzy brown skin.¹ Kiwis are most commonly eaten raw but also serve as garnishes for desserts or as ingredients in processed foods.¹ Technically a berry, kiwis grow in thick bundles from woody vines with heart-shaped leaves.
History
Kiwis are native to the temperate Yangtze Valley that runs through the middle of China. The fruits were regarded as nutritious and medicinal in China, remaining a local delicacy there for much of history.⁶ That was until the early 20th century when seeds were brought to New Zealand to be cultivated as a curiosity.¹ There the kiwi’s popularity blossomed, eventually earning the fondness of US servicemembers stationed in New Zealand during WW2. Kiwis were grown and sold in the United States as early as the 1930s as Chinese gooseberries, but their popularity really took hold after the war. Starting in the 1950s, significant quantities of the fruit began to be sold and cultivated in the US under the now-popular name “Kiwi”. ⁴
The Name
The original Chinese name for the kiwi is pronounced “Míhóutáo”, which translates to “Macaque Peach” in English. Rhesus macaque monkeys are native to the Yangtze Valley, and as enthusiastic fruit eaters, they are very fond of the native kiwis that grow there.
In New Zealand, the fruit was initially referred to as the “Chinese Gooseberry”, because it reminded locals of another delicious fruit at the time.⁴ As the popularity of the kiwi grew, so did the desire for a shorter and sweeter name. Eventually, growers settled on the name “kiwi” as an homage to New Zealand’s growing regions and the islands’ small, fuzzy, flightless bird.⁷
Nutrition
Kiwis are nutritious. They are packed with dietary fiber, as well as vitamins C, E, and K. Gram for gram, kiwis actually have more vitamin C than oranges (93mg per 100g Kiwi vs 53mg per 100g Orange). They also have a comparable amount of potassium to that of a banana (312mg per 100g Kiwi vs 358mg per 100g Banana). Kiwis make an excellent source of energy-boosting fruit-based sugars.
Eating Kiwis
Most of us already know the classic peel-and-slice method of eating kiwis but there are so many more ways to incorporate them into your diet. By cutting a kiwi in half, you end up with two convenient “bowls” of fruit that can simply be spooned out of their skins.
Kiwis also make great jams or preserves that can be used in baked goods. They can also be freeze-dried to retain their flavor.
Kiwis contain an enzyme called “Actinidain” which has meat tenderizing properties. It is used commercially in the meat industry but can also be used in your kitchen to marinate roasts so they cook tender and flavorful.
While it may not seem so looking at it, the kiwi’s skin is actually edible. The skin can be bit into raw if you don’t mind, or you can throw the entire kiwi into a blender to make for a fibrous and low-effort smoothie. The skin is a good source of fiber, folate, and vitamin E.
Varieties
There are around 50 species of kiwi in the genus Actinidia. Above all, Actinidia deliciosa, or the common kiwi, produces the most popular fruit and is the most widely cultivated. While there are dozens of different kiwi varieties grown commercially across species, the most recognizable is the “Hayward”. ⁹‘⁷’³
The Hayward has bright green fruit that is sweet with mild acidity. It is covered in an iconic fuzzy brown skin that is easy to peel. Its long shelf-life results in less spoilage and greater longevity.⁹ These factors make the Hayward the preferred variety for California growers but it isn’t the only one available on the market.
The Mega Kiwi is a new variety that is gaining popularity in California. As its name suggests, the fruit is much larger than a regular kiwi but with the same fuzzy skin and sweet green flesh.
The golden kiwi is a popular variety in New Zealand and elsewhere abroad. It has thinner skin, fewer seeds, and a gold-colored flesh that is softer and sweeter than the Hayward variety. It has been grown here but it is still rare.
As kiwis are technically berries there’s a type of kiwi that is bite-sized with thin skin that you can simply pop in your mouth. This variety is more cold-resistant, making the Pacific Northwest a better growing region. These kiwiberries are an interesting novelty that are gaining popularity as acreage increases.
Global Production
The kiwi has proven to be a versatile fruit that flourishes across the world. Major growing regions are found in China, Japan, South Korea, Italy, France, Greece, New Zealand, and California.⁵
Globally, over 4 million tons of kiwis are harvested from around 170,000 acres in cultivation.⁸ Locally, California produces 50,000 tons of fruit annually from 7,000 acres across the state.⁸’⁷ California is best known for growing crops like grapes, citrus, and tree nuts. The volume of kiwi production in California doesn’t quite match those giants, but it is significant.¹²
The acreage of kiwis grown in California is roughly on par with artichokes and pumpkins. California is the ideal region to grow kiwis in the United States, and has around 98% of the country’s acreage.
Growing Regions
Kiwis grow well in California’s temperate river valleys. The Central Valley and Central Coast Region serve as the major growing regions with more acreage in smaller valleys and foothill districts. As a shorthand, kiwis tend to grow well in peach-growing regions.⁹
Soil
Silt and sandy loam soils are best. Soil should have good drainage as kiwis are sensitive to standing water, particularly when the buds break in spring. Ideal soil pH is between 5.6 & 6.0 with an upper limit of 7.3.²’⁹ Salts should be limited and supplemental calcium may be needed.⁰ Soil depth should be 3 feet or similar to that of a peach orchard.
Water
Kiwis require ample water, particularly in regions with hotter summers. Between rainfall and irrigation, an acre of kiwi vines should receive between 6000 and 10000 gallons of water daily, depending on the temperature.⁹ Kiwis require more water than California’s vineyards but can grow with less than is used for citrus or tree nut groves.¹³ Drip irrigation is ideal, as canopy sprinklers are less efficient due to leaf runoff.
Temperature & Sun
Hayward kiwis require winter temperatures below 45⁰F for at least 600 hours for the fruit to set. The vine is cold-hardy but may experience damage at temperatures below 10⁰F. Kiwis hold up in temperatures up to 114⁰F but often benefit from a shade cloth in summer to reduce wilting.¹⁰’⁹’²
Growing Season
Kiwis need 225-240 frost-free days for a successful season. Vines produce leaves in March, flowers in May, fruit over the summer, and are generally harvested from October to November.⁹ Vines hit their stride after 5 years and have been known to be productive for up to 40 years.¹⁴
Planting
Kiwi vines are dioecious, meaning the plants come in both male and female varieties. Male plants do not bear fruit but need to be planted for proper pollination of fruit-bearing female plants. A 1-to-8 ratio of male to female plants is ideal with good access to pollinators.
Kiwi vines are typically trained to either a pergola or T-bar style trellis system to support the weight of the fruit and allow for easy harvesting. Vines should be planted 15 feet apart to account for ample root space, resulting in 150-175 fruiting vines per acre.
Vine Maturation
It takes 4 years for a kiwi vine to bear commercial quantities of fruit. Initial planting of a kiwi vine should be done with a root cutting of the preferred variety placed next to a stake that the vine can climb.
The goal in year one is to develop a single, straight trunk trained to the trellis. Other shoots should be trimmed so the main vine can reach the top of the trellis and begin to move laterally down the cordon.
A light crop will be produced during the second year under good conditions. The goal this season is to establish two separate cordons (horizontal growths on trellis) for each vine. Prune & desucker to maintain growth in the main vine.
In year three the cordons should begin to touch their neighbors. From there, canes should spread laterally across the trellis to form a canopy with adjacent vines.
Kiwi vines will start bearing full loads of fruit in year four. Female vines should be pruned vigorously in winter to remove older fruiting shoots so that fresh ones form. Male vines should be pruned only lightly to maximize the number of flowers that appear to facilitate pollination.
Harvesting
Harvests occur from October to November depending on region. Fruit should be picked gently by hand with cotton gloves so as not to harm the skin. Pickers should place fruit carefully in cloth slings before transfer to lugs. Fruit should be cooled to 32⁰-40⁰F within 24 hours of picking.²
Storage
Kiwis are picked when they are “vineripe”, meaning that they have all their sugars but simply need to experience a ripening period off the vine. By packing and storing kiwis quickly, that ripening can be delayed until the fruit is ready to hit the shelves. Fruit should be packed immediately after picking in sized trays, then wrapped in polyethylene plastic to limit air exposure. Exposure to airborne ethylene will cause kiwis to prematurely ripen in storage. As such, kiwis should be stored separately from ethylene-emitting fruits and combustion-operated vehicles or forklifts. Proper cold storage at 32⁰F will allow Hayward kiwis to stay firm for 3-6 months.
Threats
High winds present a threat to kiwis, resulting in damaged fruit and vines.² Commercial kiwis also have some sensitivity to frost and hail damage.² Pests like root-rot nematodes, leafroller caterpillars, greedy-scale insects, boxelder bugs, and especially thrips can damage kiwi plants. ¹¹’² Diseases like Phytophthora Crown Gall can infect and kill kiwi vines. After harvest kiwi fruits are susceptible to Botrytis gray mold and should be stored in a dry environment.¹¹
Commercial kiwi vines are bred for hardiness but remain vulnerable to damage from periods of extreme temperatures caused by climate change. Shade cloths should be kept handy to alleviate stretches of extreme heat.
Sustainability
The large commercial varieties of kiwis help make the fruit more sustainable to produce. Their hardiness and size make acreage more efficient and energy use less intensive. As kiwis have relatively few pest problems, they also do not require a large load of pesticides. But there are still ways to improve kiwi cultivation to make it more sustainable.
Water usage can be reduced through the installation of drip irrigators. As kiwi cultivation areas get great sun, solar panels are an excellent way to offset the energy usage from irrigation and refrigeration. Composting of prunings also serves well as fertilizer or as animal feed in an integrated farm.
Organic Kiwis
With their low pesticide load, kiwis lend themselves well to organic cultivation. Still, innovative techniques must be used to manage an organic kiwi farm. Without synthetic herbicides, extra weed management steps should be taken to ensure kiwi vine health. Weeds can be eliminated organically through the soil solarization method, in which a plastic sheet is placed around the kiwi vines to trap sunlight and overheat any potential weeds. In integrated farms, weeding animals like goats, sheep, or geese can cut down on row weeds.
The Future of Kiwi Farming
As in many aspects of life, kiwi farming is beginning to see the benefits of cutting edge technology. In addition to the use of solar panels, farmers are beginning to utilize AI-assisted irrigation systems to improve the efficiency of their operations. These systems monitor each vine making decisions on how much water they need, thus preventing wasted water or over irrigating. Some prototype kiwi picking robots have also been trialed here and in New Zealand, allowing for a more efficient harvest and less fruit wastage.
Conclusion
The kiwi is a unique fruit with a fantastic backstory. As it’s farmed right here in California, the local production makes it a sustainable choice for your fruit bowl. Thanks for watching and enjoy your next bite of kiwi!
Sources:
2 – Growing Kiwifruit – Oregon State
3 – Home Stratosphere – Types of Kiwi Fruit
4 – New Zealand History – Kiwifruit
5 – Zespri Site
6 – Facts.net Kiwis
7 – CalHarvest
8 – Atlas Big
9 – UC Davis
10 – Kliewer Interview
11 – Agrifarming How to Grow Kiwis in USA
12 – 2021 California Agricultural Overview
