RELATIVE HARDINESS TO FREEZING OF LAMINAE, ROOTS AND TILLERS OF TALL FESCUE

s ummary Tall fescue ( Festuca arundinacea Schreb. cv. S. 170) plants grown in the field and in controlled environments (mainly differing in temperature; photoperiod 12 or 16 h) were divided into laminae, roots and trimmed tillers and these were exposed to frost in a bath. Laminae and tillers hardened as much in some controlled environments as they did in the field (measured in December); a photon flux density of 110 μ mol m −2 s −1 was adequate for this. Generally, growth at low temperatures increased the hardiness of laminae and tillers; roots from plants grown at 16/14°C or at 6/4°C (day/night) were equally hardy. Laminae were hardier when they were taken from plants grown in nutrient depleted soil. The hardiness of the laminae to extension of the period of exposure (from 45 min to 24 h) was not increased by growth in 6/4°C. Hardiness of the different parts of tall fescue was compared using the highest temperature at which significant damage occurred. Laminae from the hardiest plants were hardier than the tillers; on other occasions the hardiness of laminae and tillers was close. Roots (from controlled environments) were less hardy than laminae and tillers. The hardinesses of laminae and tillers were not correlated, partly because the tillers de‐hardened during a prolonged period of growth at 6/4°C; this may have been related to reproductive development. With the exception of the last point, the observations suggest that the relative degree of frost hardening of the different parts might often be related to the likely relative intensity of the frost to which they might be exposed.