Relative flov'cr-bud hardiness was established for 4l cultivars of peach by survey of natural bud mortality follo',ving critical January temperatures in the years 1963, 1965 and 1966. Impedance to electric current (lffio cycle/sec) and scion diametel u'ere shown to be-closely related with established l6vels of hardiness, and their relationship is direct and inverse, respectively. Detailed study of impedance alone for reple_-sentative hardv. medium-tendbr and tender cuitil'ars risulted in failure to differentiate becrveen establishcd hardiness groups as a consequence of variability amributable to scion diameter influence. Incorporation of botl-r impedance and diameter measures facilitated the differentiation of nredium-tender and hardy from tender cultivars, but only at periods of maxinum flower-bud hardiness. Thc impedance method was used effectively to establish the periodicity, and pafticularly the minimum and maximum levels, of bud hardiness. Its application in differentiating between hardiness levels in cultir.ars rvhen integraced with scion diameter observations u'as confinled b)' artificial-freezing srudies.The application of these methods is restricted to bearing trees, since neicher impedance nor diameter of non-bearinq trees could be related to the hardiness responses exhibited b)'bearin€i trees of"the same cultivars.

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