INTRODUCTION: First, let me say that golden kiwifruit are complicated. A robust deciduous vine from China, the plants are dioecious (there’s a male plant and a female plant). However, it can’t be just any male. It has to be the right male, one that provides pollen when the female flower is receptive. It’s all about timing. The vine has plenty of attributes. This is a super fruit, one packed with vitamins and minerals. It can live over a hundred years and trunks over 1′ wide are not unheard of. There’s an economic message here as well. In a well managed operation, yields of 40,000 to 50,000 lbs. per acre are feasible. With $2.99 per lb. clamshells the norm in the produce aisle, you do the math. The cost of building a trellis or pergola system is high ($10-$20,000 per acre), due no doubt to the engineering needed to deal with 60,000 lbs per acre weight. Add up the trunks, branches, leaves, fruit and get a big rain, well, that’s a challenge. The green and golden kiwifruit impact on the global market place is exciting. It’s a new crop that has succeeded. Increasing market share is a global kiwifruit talent in the last few decades. Part of industry growth is simple economics and having tasty fruit in front of consumers.
THE GENUS ACTINIDIA: There are over 60 species of Kiwis in southeast Asia. While native to China, New Zealand can be given credit for introducing the fruit to the global marketplace in a big way. Commercially, the green kiwifruit (Actinidia deliciosa) dominates world production and has an interesting history in the global market place. Golden kiwifruit (Atinidia chinensis) are a relative newcomer and production is growing at a very fast clip. Demand continues to increase. There’s another market kiwifruit, Actinidia arguta, the kiwiberry which is smaller, smooth skinned and lacks the storage ability of green or golden kiwifruit. It’s sweet but has a short shelf life. For the serious student, Dr. Huang Hongwen’s 2014 publication, “Kiwifruit: The Genus Actinidia”, is the definitive text. With over 313 pages, it’s an intense coverage of the genus (Science Press Beijing; ISBN: 978-0-12-803066-0).
KIWIS IN CHINA: I have been working short term consultancies in China since 1997. Most of my work is focused on the Taxodium Improvement Program (baldcypress) at the Nanjing Botanical Garden with Professor Yin Yunlong’s team, and the Blueberry Research Institute program of Professor Yu Hong and retired Professor He Shanan. Over many years we have become fast friends and I have been witness to the dynamic growth of China’s nursery and blueberry industry.
Over the years, I had seen Kiwifruit plantations and had some interest but it wasn’t until our first crop of golden kiwifruit at SFASU that my interest was boosted. I wanted to visit the kiwifruit program at the Hubei Fruit and Tea Institute and during an Aug 2015 visit, Yu Hong made it happen. My host was Dr. Lei Zhang (English name ‘Jane’). Jane is a high energy young scientist who recently coauthored a publication on the genome Actinidia (kiwi) in Nature Communications in 2013. I remarked at our first meeting that after such an accomplishment at such a young age, the administrators would only be satisfied now if she came home with the Nobel Prize. Everyone thought that was hilarious – and probably true. In addition to cultural studies with kiwi, she had an active breeding program in place with twenty advanced selections in final evaluation stage and many others further down the pipeline. While at the Institute, we met with Zhongqi Qin, Director of the Institute, who provided us with gracious hospitality and a tour of the research farm. I enjoyed meeting Professor Yang Fuchen, who works with blueberries and pears, and it was great to see healthy blueberry plants in his studies.
While at Hubei, I learned that our two Auburn-introduced varieties, Actinidia chinensis ‘AU Golden Dragon’ and ‘AU Golden Sunshine’, were actually named ‘Jinnong’ and ‘Jinyang’ in China. Jane told me that ‘nong’ pronounces similar with ‘long’ which means ‘dragon’ in English, and ‘yang’ means sun and sunshine. Both were selected in the 1980s, after an extensive field investigation which began in 1978. ‘AU Golden Sunshine’ was selected from the wild in September, 1982, in Chongyang country and was then grafted in the garden in Hubei. ‘AU Golden Dragon’ was a large fruit taken from a distillery and the seeds of that fruit sowed. The seedlings bore fruit in 1985 and ‘AU Golden Dragon’ was selected from that population. The golden kiwi, A. chinensis, is less popular in China than the green fleshed varieties of A. deliciosa, except the variety ‘Hongyan’, which is red fleshed with a short shelf life. She was surprised that I thought eating the skin of the golden fleshed varieties was fine. Of course, this is a country where citizens often peel grapes.
Professor Yu Hong and I also made a visit to the Wuhan Botanical Garden. This germplasm repository is home to over 50 Actinidia species, 81 varieties and over 1000 genotypes, many from the wild. Plants were in good shape, the irrigation system was in fine form and harvest was about a month away.
Over many visits, my general observations is that Chinese growers like to use raised beds, build a strong infrastructure with concrete posts and high tensile wire. They know what they’re doing. Growers prefer a well drained condition for the plant; raised beds and berms are typical.
VARIETIES: The varietal picture for golden kiwifruit in the Gulf South is rather simple – and sparse. There are essentially three female varieties and one male variety with considerable promise at SFA Gardens. We need more. Dr. Hongwen Huang was a PhD student at Auburn (1990-1994) and provided the original cuttings of ‘AU-Golden Dragon’ and ‘AU-Golden Sunshine’ to Dr. Joe Norton, his advisor during that period. After a very productive career as Director and Professor at the Wuhan Botanical Garden, he is currently the Director of the South China Botanical Garden. After several years of fruiting, Auburn University and the Hubei Institute of Fruit and Tea signed an agreement, the two varieties were patented in 2007 and plants are on the market, albeit there have been a few issues on availability and pricing. For those interested, the Gold Kiwi Group has a website that describes product and availability of the two patented varieties that have performed well at SFA Gardens: http://growaukiwi.info/contact.htm
The production data from our small research plot is below.
HARVEST CONCLUSIONS: In the SFA research plots, there appears to be a correlation between chilling hours and yield. We are also convinced there is only one male variety (CK3) functioning as an effective pollinator. ‘Tiger’ and ‘Author’ exhibit poor flowering. It’s fortunate that the flowering of ‘CK3’ coincides with the bloom period of ‘AU Golden Dragon’, perhaps explaining the good yield of that variety. ‘AU Golden Sunshine’ is slightly later flowering and misses some of CK3’s floral strength, catching it as the flowers wane. With that in mind we decided to hand pollinate. in 2018, pollen was flown in from Doug Phillips, a California grower, the effort facilitated by Ross Stevenson of Miko Asia, Ltd. Ross is a New Zealand kiwifruit grower with production in Chile and other countries and is perhaps interested in expanding his efforts into East Texas. In 2018, flowers of both Golden Dragon and Golden Sunshine were hand pollinated and both varieties produced a fine crop.
CONSUMER SURVEY: The general consensus is quality is good. For the 2015 harvest of ‘Golden Dragon’ fruit, over 60 participants were given a bag and a survey form. On a 0 to 10 scale (with 0= horrible and 10=fantastic), the crop came in at 8.84. In our original planting, we have three female varieties, ‘AU Golden Dragon’, ‘AU Golden Sunshine’, and ‘Au Fitzgerald’ coupled with three males ‘CK3’, ‘Tiger’, and ‘AU Authur’, respectively. AU Golden Dragon’ has been the high performer at SFA probably due to its close proximity to the great flowering of the male ‘CK3’. As part of the 2018 crop, we undertook a Consumer preference survey with 110 respondents that yielded the following information: 1) only 21% had ever eaten golden kiwifruit. 2) on a 0-10 scale, golden kiwifruit averaged 8.72 on an overall quality index. 3) 83% who ate golden kiwifruit thought eating the skin was fine. 4) 72% preferred golden kiwifruit over green. 5) 96% said they would buy the fruit in the grocery store. Our conclusion here is that our golden kiwifruit crop passed muster.
ROOTSTOCKS: For a Texas industry to develop, it’s generally accepted that golden kiwifruit need to be grafted on an accepted rootstock. Most commercial plants are grafted on A. deliciosa, in particular. While this has to do with resistance to diseases (Psa, in particular), there’s perhaps another reason in support of rootstocks. By grafting golden kiwifruit to a green rootstock, the resultant vine is less vigorous than on its own roots, thus there are fewer hours pruning and training. While SFASU planted rooted varieties of golden kiwifruit and they have performed well on their own roots, it is still the general consensus that using a rootstock is advisable. We are taking that tact. In 2017, Ross Stevenson of Miko Asia, Ltd., sent seed of “Bruno’ to the SFA Gardens. ‘Bruno’ is a green kiwifruit variety often used as a rootstock. Seed was germinated and 4000 plants potted at the SFA Gardens greenhouse. Plants were transferred to one gallon containers and grown through the winter (Dec 2017-Mar 2018) in an outdoor nursery.
Young kiwifruit plants are more susceptible to freeze injury in the first few winters but older plants are quite tolerant of temps into the low teens and even single digits. In January 2018 a very hard freeze (two nights at 10oF) killed almost 50% of the 4000 plants, in spite of being covered with pine straw and frost fabric. The remainder recovered well and have enjoyed a vigorous growing season. Over 2000 healthy plants are being prepared for the winter ahead and will be planted in cooperator fields in March 2019. These plants will be grafted to improved varieties of golden and green kiwifruit beginning in 2020. Related to the rootstock project, we have received notification that seven cultivars of green and golden kiwifruit varieties (a Miko Asia, Ltd. introduction) will be released from USDA, Beltsville, MD quarantine to our Texas program and a cooperating farm in California in February 2019. Those plants will be multiplied at SFASU and TAMU to provide scion wood for grafting to the rootstocks set in the field.
SPACING: Vines should be very long lived. The first consideration is whether to go high density or not. If growers are interested in higher returns during the early years (years 3-5), then a closer spacing is in order. For high density, the strategy we recommend is that rows should be 12′ apart and plants should be 9′ apart in the row (403 plants per acre). As a high density orchard matures, every other vine can eventually be removed. A final density would be 18′ apart in the row (201 plants per acre for the final density of the orchard).
PLACEMENT OF POLLINATOR PLANTS: Placement of the male pollinator plants is important. Generally, one male plant per 5 to 8 females is considered average. Male branches can be grafted high on the females and marked so they can be pruned accordingly after flowering. There are all female orchards with pollen brought in and applied by hand, via airblast with air or water as a carrier. It’s relatively easy to tell males and females apart. The male flower has robust anthers but the pistil is rudimentary, dies away and often leaves a black lesion. The female flower has anthers but the pollen is sterile and there are multiple pistils present.
FERTILIZATION: There are few fertilization studies with kiwifruit in the deep South. Our experience lends itself to light applications of a complete. We have not fertilized our older vines for several years and they remain quite vigorous.
INFRASTRUCTURE: A strong pergola or arbor is required. The infrastructure needs to support a total weight of at least 60,000 lbs. per acre (vines, branches, leaves, rain and fruit). End post assemblies must be substantial. Line posts are less problematic but wind issues must be considered. The wire must be high tensile strength with little stretching. and is the main support for the arms of each vine.
PRUNING AND TRAINING: Whether high density or not, the structure of the vine is best as a single trunk to 6′ tall that ends with two arms running laterally. This will be the permanent feature of the vine. From the two arms will emerge shoots that should be trained to be the fruiting arm for the next year.
WINTER FREEZES AND SPRING FROSTS: We have learned the hard way that young vines are susceptible to low winter temperatures if they fall below10oF. Once flowers open in late March and early April they are, of course, susceptible to very late frosts. Fortunately, kiwifruit bloom late enough to avoid most spring frosts (i.e., peaches characteristically bloom two to four weeks earlier). Sprinkler systems for frost protection can be designed to protect vines into the low twenties.
A unique problem that has arisen with Kiwifruit is the tendency not to slide into dormancy gracefully. 2018 has been a real benchmark in some respects. Before we had our first frost, we experienced in early November 2018 a first freeze in Nacogdoches, TX, which was quite harsh with two nights a 27F. While our young container plants were unfertilized since July and placed under a lower watering regime, they still appeared vigorous before the freeze. At College Station, Texas, the research plots saw temperatures to 24.7F and damage was more severe on the young vines there. Winter freezes at Auburn and at the GroAuKiwi field have damaged young vines. This reality suggests that young vines need winter protection for the first few years in the field. We have gone to a chicken wire tube stuffed with pie straw.
TEEPEE SYSTEM: For maximizing production, growers in New Zealand have pioneered the teepee system. This system encourages shoots from the arm to climb strings on a teepee. The next winter, those long woody shoots are “laid down” over the wires of the pergola and clipped to create a roof one BRANCH thick. In the spring when growth resumes, the grower chooses shoots from the arm again and trains them to a teepee. So at any one time, there are young shoots clambering up strings, as well as a horizontal layer of shoots that were laid down in the winter. The cycle repeats.
PESTS AND DISEASES: Psa, Pseudomonas syringae pv. actinidiae, is a bacterial disease and no doubt the biggest threat. The introduction of (Psa) severely damaged the New Zealand kiwifruit industry which recovered quickly with a rigorous sanitation program and the introduction of several disease tolerant yellow-fleshed varieties. While Psa has not been found in the Gulf South, the general feeling is that it will arrive. Golden kiwifruit is considered more susceptible than green, thus the recommended use of a resistant rootstock. As for insects, scale has been a problem on a few of our older vines but is easily controlled with a dormant oil spray. Our crystal ball suggests that the Brown Marmorated Stink Bug (BMSB) is a looming threat. It was a major problem in the 2018 Alabama harvest. There have been occurrences in Texas so it’s probably just a matter of time. The Spotted Wing Drosophila is another pest new to Texas and it may be a severe problem in the years ahead. One dilemma for growers is that so few pesticides are currently labeled for Kiwifruit – simply because it’s a new crop and there has been no acreage of impact here in the Gulf South.
TEXAS DEPARTMENT OF AGRICULTURE GRANT. Since 2016, this project has been substantially funded by a Texas Department of Agriculture Specialty Crops Block Grant. We are excited to be working with Tim Hartmann and colleagues at Texas A & M University as they ramp up evaluation and research plots. In the next few years, we’ll know if kiwis are an exciting new commercial fruit for Texas – or not. Even if they’re a go in scattered small farms of the South, I’m convinced there’s a potential bigger opportunity available – one that capitalizes on mass markets and wholesale/retail nurseries to supply plants to homeowners. In the next two years there will be a transfusion of new potential varieties. Never underestimate what good gardeners can do with the right plant material. In the spring 2019 we will be planting four new cooperator sites (Two in the Mt. Pleasant area, Tyler, and Simonton, Texas).
After visiting California kiwifruit growers, we can count a few comparative advantages in East Texas: Land Cost, no need for overhead shade or fogging, Irrigation water is often readily available at low cost, and perhaps labor costs are lower. Disadvantages would include no history of production, processing or marketing and the unknowns of low chilling and spring frosts. Issues with pollination appear important to the long term success of plantings. In the next few years we will have the answers. Until then, we’ll keep planting and studying this fascinating new crop in Texas.