SEGMENT INFORMATION - Net Sales by Product Category (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Revenue from External Customer [Line Items]
Net sales	$ 3,924.1	$ 4,925.0	$ 4,131.6
U.S. Consumer | Growing media and mulch
Revenue from External Customer [Line Items]
Net sales	1,192.6	1,286.7	1,164.0
U.S. Consumer | Lawn care
Revenue from External Customer [Line Items]
Net sales	973.6	1,060.6	943.3
U.S. Consumer | Controls
Revenue from External Customer [Line Items]
Net sales	382.2	402.4	383.7
U.S. Consumer | Roundup marketing agreement
Revenue from External Customer [Line Items]
Net sales	132.3	145.2	132.7
U.S. Consumer | Other, primarily gardening
Revenue from External Customer [Line Items]
Net sales	248.1	302.8	259.8
Hawthorne
Revenue from External Customer [Line Items]
Net sales	716.2	1,424.2	1,023.1
Hawthorne | Lighting
Revenue from External Customer [Line Items]
Net sales	200.0	452.4	328.7
Hawthorne | Nutrients
Revenue from External Customer [Line Items]
Net sales	148.0	324.7	250.1
Hawthorne | Growing environment
Revenue from External Customer [Line Items]
Net sales	143.7	264.0	154.2
Hawthorne | Growing media
Revenue from External Customer [Line Items]
Net sales	119.0	192.6	148.9
Hawthorne | Other, primarily hardware
Revenue from External Customer [Line Items]
Net sales	105.5	190.5	141.2
Other
Revenue from External Customer [Line Items]
Net sales	279.1	303.1	225.0
Other | Lawn care
Revenue from External Customer [Line Items]
Net sales	92.9	99.2	73.7
Other | Growing media
Revenue from External Customer [Line Items]
Net sales	96.6	116.7	90.6
Other | Other, primarily gardening and controls
Revenue from External Customer [Line Items]
Net sales	$ 89.6	$ 87.2	$ 60.7