ACQUISITIONS AND INVESTMENTS	12 Months Ended
ACQUISITIONS AND INVESTMENTS	Sep. 30, 2021
Business Combinations [Abstract]
ACQUISITIONS AND INVESTMENTS	ACQUISITIONS AND INVESTMENTS Rhizoflora On August 13, 2021, the Company’s Hawthorne segment completed the acquisition of substantially all of the assets of Rhizoflora, Inc., manufacturer of terpene enhancing nutrient products Terpinator® and Purpinator®, for $33.7. The valuation of the acquired assets included (i) $0.5 of inventory, (ii) $10.9 of finite-lived identifiable intangible assets and (iii) $22.2 of tax-deductible goodwill. Identifiable intangible assets included tradenames, customer relationships and non-compete agreements with useful lives ranging between 5 and 25 years. The estimated fair values of the identifiable intangible assets were determined using an income-based approach, which includes market participant expectations of cash flows that an asset will generate over the remaining useful life discounted to present value using an appropriate discount rate. The Hawthorne Collective On August 24, 2021, the Company’s newly formed subsidiary, The Hawthorne Collective, Inc., made its initial investment under the Company’s strategic minority non-equity investment initiative in the form of a $150.0 six-year convertible note issued to the Company by Toronto-based RIV Capital Inc. (“RIV Capital”) (CSE: RIV) (OTC: CNPOF), a cannabis investment and acquisition firm listed on the Canadian Securities Exchange. The note accrues interest at 2 percent annually for the first two years and provides additional follow-on investment rights. Accrued interest will be payable to The Hawthorne Collective, Inc. at maturity or will be included in the conversion value of the note at the time of conversion. The conversion feature, which is based upon the RIV Capital closing stock price on August 9, 2021, would provide the Company with approximately 42 percent ownership of RIV Capital if it exercises the conversion feature. In connection with the Company’s investment, RIV Capital increased the size of its Board of Directors from four to seven members, and added three nominees of the Company to the Board of Directors. The Company will not have control of or an active day-to-day role in RIV Capital nor any of the companies in which RIV Capital invests. RIV Capital has agreed to use the funds for general corporate and other lawful purposes, which could include acquisitions, and has agreed that the funds will not be used in connection with or for any cannabis or cannabis-related operations in the U.S. unless and until such operations comply with all applicable U.S. federal laws. During the fourth quarter of fiscal 2021, The Hawthorne Collective, Inc. made additional minority non-equity investments of $43.1 million in other entities focused on branded cannabis and high quality genetics. These additional investments also include conversion features that would provide the Company with minority ownership interests if it exercises the conversion features. The investments include restrictions that the funds will not be used in connection with or for any cannabis or cannabis-related operations in the U.S. unless and until such operations comply with all applicable U.S. federal laws. Hydro-Logic On August 27, 2021, the Company’s Hawthorne segment completed the acquisition of substantially all of the assets of Hydro-Logic Purification Systems, Inc., a leading provider of products, accessories and systems for water filtration and purification, for $66.7. The purchase price is subject to a post-closing net working capital adjustment for which the Company has accrued its expected obligation of $1.7 as of September 30, 2021 in the “Other current liabilities” line in the Consolidated Balance Sheets. The valuation of the acquired assets included (i) $6.1 of inventory and accounts receivable, (ii) $1.7 of noncurrent assets, (iii) $2.5 of other liabilities, (iv) $23.1 of finite-lived identifiable intangible assets and (v) $38.3 of tax-deductible goodwill. Identifiable intangible assets included tradenames, customer relationships and non-complete agreements with useful lives ranging between 5 and 25 years. The estimated fair values of the identifiable intangible assets were determined using an income-based approach, which includes market participant expectations of cash flows that an asset will generate over the remaining useful life discounted to present value using an appropriate discount rate. AeroGrow On November 11, 2020, the Company entered into an agreement and plan of merger to acquire the remaining outstanding shares of AeroGrow for cash consideration of $3.00 per share, or approximately $20.1. The merger closed on February 26, 2021. Prior to closing, SMG Growing Media, Inc., a wholly-owned subsidiary of Scotts Miracle-Gro, was the holder of 80.5% of the outstanding shares of AeroGrow. The closing date carrying value of the noncontrolling interest was $6.7 and the $13.4 difference between the purchase price and carrying value was recognized in the “Common shares and capital in excess of $0.01 stated value per share” line within “Total equity—controlling interest” in the Consolidated Balance Sheets.