Sec Form 3 Filing - PARKER MARK S @ HYDROFARM HOLDINGS GROUP, INC. - 2022-02-25

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person PARKER MARK S 2. Issuer Name and Ticker or Trading Symbol HYDROFARM HOLDINGS GROUP, INC. [ HYFM] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) Executive Vice President (Last) (First) (Middle) 1510 MAIN STREET 3. Date of Earliest Transaction (MM/DD/YY) 02/25/2022 (Street) SHOEMAKERSVILLE, PA19526 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock, $0.0001 par value per share( 1 ) 28,117 D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Incentive Stock Option $ 8.428 ( 2 ) 06/10/2029 Common Stock, $0.0001 par value per share 39,674 D Non-Qualified Stock Option $ 8.428 ( 3 ) 06/10/2029 Common Stock, $0.0001 par value per share 4,819 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other PARKER MARK S 1510 MAIN STREET SHOEMAKERSVILLE, PA19526 Executive Vice President Signatures /s/ Mark Parker 03/10/2022 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Includes 14,831 restricted stock units ("RSUs") granted to Mr. Parker on October 31, 2020 under the Issuer's 2019 Equity Incentive Plan (the "Plan"), 1,339 of which were previously withheld to satisfy tax withholding obligations. The RSUs vested 25% on October 31, 2021 and then vest ratably over 36 months. ( 2 )On June 10, 2019, Mr. Parker was granted 39,674 incentive stock options ("ISOs") under the Plan. The ISOs vested 25% on June 10, 2020 and then vest ratably over 36 months. ( 3 )On June 10, 2019, Mr. Parker was granted 4,819 non-qualified stock options ("NQs") under the Plan. The NQs vested 25% on June 10, 2020 and then vest ratably over 36 months.

Remarks: Exhibit List - Exhibit 24 - Power of Attorney

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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