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Summer Fruits Choosing a peach Compatibility issues between rootstock and scion can greatly dwarf a tree. This is Redhaven on Krymsk 2. Most plantings are still on seedling pretty much is that way," says Dr. Greg Reighard, horticul- tural professor at Clemson University in South Carolina. Most peaches are planted on seedling rootstocks chosen to fit regional conditions. But increasingly, growers have other choices. Reighard is chair of the peach section of the NC-140 project, in which T roots, but growers increasingly have other choices. by Richard Lehnert he easiest way for a peach grower to select a rootstock is to take what the nursery sends— and assume the nursery knows what a grower in that production region needs. "That's been the traditional way, and still Greg Reighard looks over Guardian peach rootstocks being grown in a Tennessee nursery. Guardian was developed by scientists at USDA and Clemson University to provide resistance to nematodes without the use of chemical fumigants. horticulturists at 16 locations across North America evaluate peach root- stocks and annually meet to report and discuss their findings. Most information has come from plantings made in 1994, 2001, 2002, and 2009. They've developed quite a body of information, much of it posted at the Web site www.nc140.org. Vigorous growth Peaches are not like apples, Reighard noted. Peaches bear fruit on one- year-old wood, so there's a continuing need for vigorous growth. While most growers would like somewhat smaller trees, he said, they can't afford to give up new growth, nor can they live with lower yields and smaller fruit, both of which have been problems with trees on dwarfing roots. But progress is being made toward smaller trees. Peaches are naturally somewhat smaller in stature compared to other tree fruits. Put- ting them on nonpeach roots can either invigorate or dwarf them, depending on the Prunus species or hybrid selected, he said. While peach breeders may seem behind apple breeders in developing dwarfing root- stocks to manage tree size, peaches are ahead of apples in developing rootstocks to solve problems relating to soils, pests, and diseases. Growers in various regions of the country choose rootstocks based on nematode pressures, soil pH, replant-associated diseases, soil fungal pathogens like Armillaria, peach tree short life, and cold hardiness. Until about 1930, peach growers used peach seedlings like Tennessee Natural and Bailey as rootstocks. After that, they began to use more Lovell or Halford seedlings raised from pits collected at canneries. After about 1960, when more attention was focused on cold hardiness, Harrow Blood from Ontario, Canada, and Siberian C from China, were introduced. Still, in the northern peach-growing areas, growers are still most likely to plant Bailey or Lovell, which are cold hardy enough for most conditions. In the Southeast and California, pressure from nematodes led to the search for resist- ant rootstocks. The USDA Rootstock Breeding Program released Nemaguard in 1959, Bacterial canker is a component of peach tree short life, and one purpose of evaluating rootstocks is to find resistance. 22 JULY 2012 GOOD FRUIT GROWER