Abstract Growth retardants may increase seed yield in herbage legumes. The growth retardant paclobutrazol was applied at a rate of 1.0 kg a.i./ha at either inflorescence initiation (9 October) or first flower bud appearance (2 November) to four white clover cultivars (#x2018;Grasslands Kopu#x2019;, #x2018;Grasslands Pilau#x2019;, #x2018;Grasslands Huia#x2019;, #x2018;Grasslands Tahora#x2019;) which differed in leaf size from large to small, and the effects were observed. Paclobutrazol application in October significantly increased inflorescence numbers in all four cultivars, and advanced their appearance in all but Kopu. November application initially delayed inflorescence appearance, but then increased the rate of inflorescence appearance and significantly increased inflorescence number. Leaf size was reduced in all cultivars, and inflorescences were elevated above the canopy because petiole length was reduced. The November application significantly increased seed yield in all four cultivars, whereas the October application increased seed yield in Pitau and Tahora, but not in Kopu or Huia. Seed yield increases were associated either with increased harvestable inflorescences, or increased seeds per inflorescence, but these responses differed with cultivar and application time. The implications of these results and the need for further research are discussed.
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