Hardy kiwi or kiwiberries (Actinidia spp.) are a re-emerging specialty fruit in Ontario (Fig 1). These flavourful, bite-sized, fruit have smooth edible skins and are typically sweeter than fuzzy kiwi (Actinidia deliciosa). The predominant fruiting types of kiwiberries used in commercial production are A. arguta and A. kolomikta.
Fig 1: ‘Jumbo’ hardy kiwi growing at the Simcoe Research Station, Norfolk County, Ontario.
The University of New Hampshire (UNH) kiwiberry research and breeding program has recently released a new online production guide for kiwiberry growers. The guide includes information on vineyard set-up, trellis design, seasonal agronomic requirements for the crop, and harvest/post-harvest methods. The production guide is available at http://www.noreastkiwiberries.com/production-guide
Kiwiberries have a long history in Ontario but very little commercial production currently exists. With changing markets and consumer preferences, this specialty fruit is re-emerging in Ontario grocery stores (imported) and on a few farms experimenting with domestic production. With new production comes the opportunity to learn (re-learn) some of the basic agronomic requirements for the crop along with harvesting practices to optimize post-harvest fruit quality.
Harvesting kiwiberries:
In Ontario, kiwiberries are typically harvested 60+ days after bloom (usually mid-September). Guidelines in the UNH production guide suggest a once-over harvest of the kiwiberries when they are still hard and allowing the fruit to soften in storage before marketing (Fig 2). Educating consumers on allowing the fruit to soften before eating is a key message for this type of harvest and marketing technique.
Fig 2: Once-over harvest of ‘Jumbo’ hardy kiwi at the Simcoe Research Station, Norfolk County, Ontario.
Guidelines for determining when the fruit is ready to harvest:
1. Black Seed Stage: randomly sample fruit from the vineyard and cut open in a cross-section to determine if the fruit have reached physiological maturity known as the ‘black seed stage’. All seeds inside the fruit should be black (Fig 3).
Fig 3: Cross-section and lengthwise section of hardy kiwi at ‘black seed stage’.
2. Sugar content: although most of the fruit will still be hard and bitter at this point, using a Brix metre (a common tool providing a measure of soluble solids in the fruit) will provide a guide to the most appropriate time for harvesting the fruit for optimal ripening off the vine. UNH suggests fruit should be in the 6-8°Brix level at harvest which will allow the fruit to ripen to >20°Brix post harvest (once fruit have softened). Once the fruit have completely softened they are ready for consumption.
For more information on hardy kiwi production and post-harvest resources for Ontario and the Northeast USA, please visit the following links:
1. University of New Hampshire Production Guide: http://www.noreastkiwiberries.com/production-guide
2. OMAFRA Specialty Cropportunities Hardy Kiwi Crop Profile: http://www.omafra.gov.on.ca/CropOp/en/spec_fruit/vine_fruit/kiwi.html
3. Penn State Extension: https://extension.psu.edu/hardy-kiwi-in-the-home-fruit-planting
4. UC Davis Post-harvest Storage Recommendations for Fruits and Vegetables: http://postharvest.ucdavis.edu/Commodity_Resources/Storage_Recommendations/