Green’s Dictionary of Slang

1. (also early hour, happy half-hour) in pl., flowers [orig. use by Covent Garden Market porters].

1935		A.J. Pollock Und. Speaks n.p.: Happy hours, flowers.
1960, 1975		Wentworth & Flexner DAS 648/1: happy half-hours – flowers.
1969		S.T. Kendall Up the Frog 23: ’Appy ’arf hours – Flowers. [Ibid.] 30: Early hours – Flowers.
1971		J. Jones Rhy. Cockney Sl. 15: Early Hours – Flowers.
1992		R. Puxley Cockney Rabbit.
2002		M. Coles More Bible in Cockney 12: Grass and the early hours grow for a while.

2. (Aus.) a shower.

2002		B. Kirkpatrick Wicked Cockney Rhy. Sl.
2002		Pete’s Aussie Sl. Home Page 🌐 happy hour: a shower.