Scion & Rootstock Selection
Rootstocks not only provide below ground protection from pests, but can also influence scion growth. Dwarfing rootstocks reduce tree height by producing a less vigorous canopy. A reduced canopy can be beneficial because it enables hand harvesting and limits otherwise intensive pruning required on peach and nectarine. Currently in California the most common rootstocks used for peach and nectarine are ‘Lovell’ and ‘Nemaguard’. Two new releases, ‘Controller 5’ and ‘Controller 9’, are promising dwarfing rootstocks reducing the tree height 50% and 90%, respectively, compared to ‘Nemaguard’ (DeJong T. M., Johnson, Doyle, & Ramming, 2005). The rootstock used mostly in northern California is ‘Lovell’ because of its cold hardiness and tolerance of wet soils. In the San Joaquin Valley ‘Nemaguard’ is common because it is resistant to root knot nematode.
Peach budding compatibility is enhanced when scions are budded onto peach or peach x almond rootstock. Graft incompatibility has been observed for peach grafted onto almond, plum (Zarrouk, Aparicio, Gogorcena, & Moreno, 2005), apricot or other interspecific hybrid rootstock. The Fruit Report, a website developed by Scott Johnson, includes a comprehensive database of peach, nectarine, and plum rootstocks developed for use in California and links to scientific reports. The rootstock variety database is organized both by rootstock name and characteristic (ex. waterlogging tolerance, vigor, Nematode resistance etc.).
Peach and nectarine, Prunus persica, is grown in California for fresh market consumption or processing. Both peach and nectarines are separated into several morphological or production varieties including clingstone, freestone, and semi-freestone. Clingstone flesh “clings” to the stone or pit, they tend to ripen earlier in the season and are generally produced for processing with a few exceptions. About 80% of California’s processing peaches are clingstone varieties (Perez, Plattner, & Baldwin, 2011). Freestone peach and nectarine flesh does not cling to the pit and tends to ripen later in the season. Freestone varieties are typically grown for fresh market sales, but are occasionally used for freezing or drying (Okie, Bacon, & Bassi, 2008). Semi-clingstone varieties are intermediate with flesh that only partially clings to the pit.
Peach and nectarine flesh is categorized by both color and texture. Fruit color is categorized as “yellow” or “white”. Yellow flesh fruit tends to ripen earlier in the growing season and exhibit a tarter flavor than white flesh fruit. Flesh texture is referred to as melting or non-melting. Non-melting fruit are best for processing because they remain firm and withstand the harshness of processing. The soft texture of melting fruit is best for fresh market consumption because the flesh softens over time. Depending on the variety, and the region the crop is growing in, peaches and nectarines can ripen from early May through late September in California. Each variety has about a 10 to 15 day ripening period and is described as an extra early, early, late, or extra late ripening variety. It is best to plant an orchard that has a variety of ripening dates to extend the growing season and distribute labor uniformly.
The Fruit Report, a website developed by Scott Johnson, includes a comprehensive database of peach, nectarine, and plum fruiting varieties grown in California. Peach, nectarine, and plum varieties are listed individually, or in order of total annual production within California from 2000-2010.