United States securities and exchange commission logo August 19, 2022 John Lindeman Chief Financial Officer Hydrofarm Holdings Group, Inc. 1510 Main Street Shoemakersville, Pennsylvania 19526 Re: HYDROFARM HOLDINGS GROUP, INC. Form 10-K for the Fiscal Year Ended December 31, 2021 Filed March 1, 2022 File No. 1-39773 Dear Mr. Lindeman: We have limited our review of your filing to the financial statements and related disclosures and have the following comments. In some of our comments, we may ask you to provide us with information so we may better understand your disclosure. Please respond to these comments within ten business days by providing the requested information or advise us as soon as possible when you will respond. If you do not believe our comments apply to your facts and circumstances, please tell us why in your response. After reviewing your response to these comments, we may have additional comments. Form 10-K for the Fiscal Year Ended December 31, 2021 Management's Discussion and Analysis of Financial Condition and Results of Operations Non-GAAP Financial Measures, page 65 1. Wherever you present "Adjusted EBITDA as a percent of sales," please revise to also present Net income (loss) as a percent of sales. Where presenting Non-GAAP measures, please present the comparable GAAP measure with equal or greater prominence. Refer to Item 10(e)(1)(i)(A) of Regulation S-K and Question 102.10 of the staff's Compliance and Disclosure Interpretations on Non-GAAP Financial Measures. Note 3. Business Combinations, page 90 2. Please tell how you considered the guidance in Rule 1-02(w), Rule 3-05, and Rules 11-01 and 11-02 of Regulation S-X for the acquisitions that occurred during 2021. John Lindeman Hydrofarm Holdings Group, Inc. August 19, 2022 Page 2 Note 16. Fair Value Measurements, page 118 3. Please provide the applicable disclosures required by ASC 820-10-50-2. In closing, we remind you that the company and its management are responsible for the accuracy and adequacy of their disclosures, notwithstanding any review, comments, action or absence of action by the staff. You may contact Ta Tanisha Meadows at (202) 551-3322 or Angela Lumley at (202) 551-3398 with any questions. FirstName LastNameJohn Lindeman Sincerely, Comapany NameHydrofarm Holdings Group, Inc. Division of Corporation Finance August 19, 2022 Page 2 Office of Trade & Services FirstName LastName