Kiwifruit Propagation
Kiwifruit
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Kiwifruit is almost exclusively propagated asexually by grafting fruiting varieties onto seedling rootstock, or using semi-hardwood or hardwood cuttings to ensure production of true to type cultivars (Tanimoto 1994). Kiwifruit seeds are not guaranteed to produce plants with desirable traits (bloom time, cane growth, fruit shape, or edibility) present in either parent. Additionally, seedlings have a long juvenile period, requiring up to seven years before sex determination is possible. As a result of these complications kiwifruit is only propagated by seed when breeding new cultivars or to produce rootstocks.
Sexual propagation
To grow kiwifruit rootstock seedlings, collect seeds from well ripened soft fruit in November. Blend fruit in a blender, push the resulting slurry through a fine mesh sieve, and place seeds in a drying oven for two weeks (Tanimoto 1994). After 2-3 weeks alternate temperatures to mimic day/night cycles (Hartman et al. 2011). To germinate seeds place them on moist sand at 34oF. After 10-14 days seedlings will germinate and should be planted into greenhouse pots containing sterile, well drained potting mix. Maintain seedlings for 3-4 months in the greenhouse at 60-80oF, then harden seedlings outdoors under a shade cloth before planting in the field (Tanimoto 1994).
Grafting
Kiwifruit growers typically obtain plants from licensed nurseries, to optimize desirable plant and fruit qualities. Commercial plants are grafted onto seedling rootstock, typically cultivars Bruno or Hayward (Beutel 1990). Bruno is a more frequently used as a rootstock because it is believed to have superior rooting ability when compared to Hayward (Tanimoto 1994). Rootstock seedlings are grown from seeds extracted from the ripe fruit. These plants grow for one year in the nursery before grafting.
In California dormant scion wood should be collected in January and scion wood should be grafted to seedling rootstock in early spring (mid to late April). Collect scion wood from vigorous shoots produced in the previous season with well-developed buds. Although grafts can be done using t-budding, whip grafting is most commonly used (Tanimoto 1994).
Micropropagation
Short meristem tips or apical shoots can be used for micropropagation of kiwifruit (Hartmann et al. 2011). However, field performance of micropropagated plants has been shown to be much worse than plants propagated by grafting or cutting (Oliveira and Fraser 2005) and micropropagation of kiwifruit is not common in California (Tanimoto 1994). The reduction in performance of micropropagated seedlings is due to delayed flowering (up to one year) and low nutrient uptake efficiency relative to plants from grafts or cuttings (Oliveira and Fraser 2005).
Cuttings
Although kiwifruit can be propagated from softwood and hardwood cuttings, softwood cuttings are preferred because they root more uniformly. Collect wood produced that season for softwood cuttings from late-April through May. Cut shoots into segments just below each leaf node. Dip the basal end of the cutting in a root growth hormone and plant in a pot with well drained sterilized soil. Once cuttings produce roots move them into a lath house for hardening three months prior to planting (Tanimoto 1994).