Spring freezing injury to peach flowers hinders consistent peach production in the southeastern United States. Delaying peach phenology would reduce the risk of a crop loss to cold. High chilling Prunus persica genotypes selected for their late flower phenology were used as 20-50 cm interstems in tests established in 1991 and 1993 near Columbia and Clemson, South Carolina, respectively. The 1991 trial was composed of 8 peach varieties (650-1000 chill hours) on interstems of Ta Tao 24 (P.I. 101686) and an unknown high chill peach (acronym PK1) budded to Lovell rootstock, The 1993 trial consisted of 22 varieties (650-1050 chill hours) budded to Ta Tao 5 (P.I. 101667) interstems on Lovell rootstock, Controls in both tests were the same varieties budded to Lovell rootstock. Observations through 1996 showed that Ta Tao 5 and 24 and PK1 interstems significantly affected bloom date, tree size, fruit yield and maturity date. Full bloom of varieties on Ta Tao interstems was delayed 1 to 13 days and about half that on the PK1 interstems. Tree trunk cross-sectional area of Ta Tao interstem trees was as much as 48% less than control trees after 6 years. Fruit yields per interstem tree were equal to or less than the controls, and fruit maturity was delayed from 1 to 9 days depending on the variety and year. PK1 interstem trees had higher yields than control trees in 1996 when 2 post-bloom freezes significantly reduced total yields.
