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Forcing of tree peony for December shipping was investigated using spring-and winterblooming cultivars. 1. By chilling 4-year-old plants with large tuberous roots of spring-blooming cultivars, two to three cut flowers were harvested per plant in late December, whereas, the same treatment with 2-year-old plants with small tuberous roots yielded only one flower per plant. The flower quality of the 4-year-old plants was equal to or slightly better than that of 2-year-old plants. 2. To force flowering by early December, winter-blooming cultivars were chilled for a short period. The flower quality of the chilled plants was much better than that of the unchilled ones.

Potted plants of `Taiyoh' and `Hanakisoi' tree peony (Paeonia suffruticosa Andr.) were treated with a foliar spray of uniconazole or paclobutrazol for shoot length control. Uniconazole sprays at 25 or 50 ppm upon sprouting effectively reduced shoot length in both cultivars. The retarding effect was greater in `Taiyoh' than in `Hanakisoi' at 25 ppm. Uniconazole treatment did not influence flower diameter or days to flowering in either cultivar. Paclobutrazol sprays at 500 and 1000 ppm were less effective in reducing `Hanakisoi' shoot length than uniconazole sprays at 25 and 50 ppm. Chemical names used: E-1-(4-chlorophenyl)-4,4-dimethyl-2-(l,2,4-triazol-l-yl)-l-pentan-3-ol (uniconazole); (1RS, 3RS)-1-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-l-yl)-l-pentan-3-ol (paclobutrazol).

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