<PAGE>

                                                                 EXHIBIT 4(m)(3)
================================================================================
                               THE SCOTTS COMPANY

                                  $400,000,000

                              SERIES A AND SERIES B
                    8.625% SENIOR SUBORDINATED NOTES DUE 2009


                              --------------------

                          SECOND SUPPLEMENTAL INDENTURE

                         Dated as of September 29, 2003

                                       To

                                    INDENTURE

                        Dated as of January 21, 1999 and

                         Amended as of February 6, 2002

                              --------------------


                         U.S. BANK NATIONAL ASSOCIATION

                                   AS TRUSTEE


================================================================================


<PAGE>


                          SECOND SUPPLEMENTAL INDENTURE

      SECOND SUPPLEMENTAL INDENTURE (this "Second Supplemental Indenture"),
dated as of September 29, 2003 by and among The Scotts Company, an Ohio
corporation (the "Company"), Scotts Manufacturing Company ("Scotts
Manufacturing," as successor by merger to Scotts Miracle-Gro Products, Inc.),
Scotts Temecula Operations, LLC ("Scotts Temecula", as successor by merger to
Republic Tool & Manufacturing Corp.) and the other guarantors named on the
signature pages hereto (with Scotts Manufacturing and Scotts Temecula, the
"Guarantors"), and U.S. Bank National Association (successor to State Street
Bank and Trust Company) as trustee under the Indenture (as defined below) (the
"Trustee").

                               W I T N E S S E T H

      WHEREAS, the Company and the Guarantors (including the predecessors of
Scotts Manufacturing and Scotts Temecula) previously duly executed and delivered
to the Trustee and the Trustee previously duly executed an indenture dated as of
January 21, 1999, as amended by the Supplemental Indenture dated as of February
6, 2002 (as so amended, the "Indenture"), pursuant to which the Company has
issued $400 million principal amount of 8.625% Senior Subordinated Notes due
2009 (the "Notes");

      WHEREAS, on September 15, 2003, the Company commenced a tender offer (the
"Tender Offer") to purchase the Notes for cash;

      WHEREAS, in connection with the Tender Offer, the Company has solicited
consents from Holders of the Notes to certain amendments to the Indenture, which
are contained in this Second Supplemental Indenture (the "Amendments");

      WHEREAS, Section 9.02 of the Indenture provides that the Company, the
Guarantors and the Trustee, with the consent of the Holders of at least a
majority in principal amount of the then outstanding Notes (including Additional
Notes, if any), may amend or supplement certain provisions of the Indenture with
respect to the Notes;

      WHEREAS, the Holders of not less than a majority in principal amount of
the outstanding Notes have consented to the Amendments; and

      WHEREAS, the Board of Directors of the Company has authorized the
execution of this Supplemental Indenture and its delivery to the Trustee;

      WHEREAS, the Company has delivered an Officers' Certificate and an Opinion
of Counsel to the Trustee pursuant to Sections 7.02, 9.02 and 13.04 of the
Indenture; and

      WHEREAS, this Second Supplemental Indenture is effective as of the date
upon which the conditions set forth in Section 3 hereof (subject to the proviso
set forth therein) are satisfied, and the Amendments effected by this Second
Supplemental Indenture will become operative with respect to the Notes on the
date the Notes that are tendered and not withdrawn are accepted for purchase and
paid for by the Company pursuant to the Tender Offer.

      NOW THEREFORE, in consideration of the foregoing and for other good and
valuable consideration, the receipt of which is hereby acknowledged, the
Company, each Guarantor and the Trustee mutually covenant and agree for the
equal and ratable benefit of the Holders of the Notes as follows:


<PAGE>


      SECTION 1. DEFINITIONS. For all purposes of the Indenture and this Second
Supplemental Indenture, except as otherwise expressly provided or unless the
context otherwise requires:

      (a) the words "herein," "hereof" and "hereunder" and other words of
similar import refer to the Indenture and this Second Supplemental Indenture as
a whole and not to any particular Article, Section or subdivision; and

      (b) capitalized terms used but not defined in this Second Supplemental
Indenture shall have the meanings assigned to them in the Indenture.

      SECTION 2. AMENDMENTS. The Indenture is hereby amended with respect to the
Notes as follows:

      (1) Section 3.09 of the Indenture is hereby eliminated in its entirety and
replaced with the words: "Section 3.09. [INTENTIONALLY OMITTED]."

      (2) Section 4.03 of the Indenture is hereby eliminated in its entirety and
replaced with the words: "Section 4.03. [INTENTIONALLY OMITTED]."

      (3) Section 4.04 of the Indenture is hereby eliminated in its entirety and
replaced with the words: "Section 4.04. [INTENTIONALLY OMITTED]."

      (4) Section 4.05 of the Indenture is hereby eliminated in its entirety and
replaced with the words: "Section 4.05. [INTENTIONALLY OMITTED]."

      (5) Section 4.07 of the Indenture is hereby eliminated in its entirety and
replaced with the words: "Section 4.07. [INTENTIONALLY OMITTED]."

      (6) Section 4.08 of the Indenture is hereby eliminated in its entirety and
replaced with the words: "Section 4.08. [INTENTIONALLY OMITTED]."

      (7) Section 4.09 of the Indenture is hereby eliminated in its entirety and
replaced with the words: "Section 4.09. [INTENTIONALLY OMITTED]."

      (8) Section 4.10 of the Indenture is hereby eliminated in its entirety and
replaced with the words: "Section 4.10. [INTENTIONALLY OMITTED]."

      (9) Section 4.11 of the Indenture is hereby eliminated in its entirety and
replaced with the words: "Section 4.11. [INTENTIONALLY OMITTED]."

      (10) Section 4.12 of the Indenture is hereby eliminated in its entirety
and replaced with the words: "Section 4.12. [INTENTIONALLY OMITTED]."

      (11) Section 4.13 of the Indenture is hereby eliminated in its entirety
and replaced with the words: "Section 4.13. [INTENTIONALLY OMITTED]."

      (12) Section 4.14 of the Indenture is hereby eliminated in its entirety
and replaced with the words: "Section 4.14. [INTENTIONALLY OMITTED]."

      (13) Section 4.15 of the Indenture is hereby eliminated in its entirety
and replaced with the words: "Section 4.15. [INTENTIONALLY OMITTED]."


<PAGE>


      (14) Section 4.16 of the Indenture is hereby eliminated in its entirety
and replaced with the words: "Section 4.16. [INTENTIONALLY OMITTED]."

      (15) Section 4.17 of the Indenture is hereby eliminated in its entirety
and replaced with the words: "Section 4.17. [INTENTIONALLY OMITTED]."

      (16) Section 4.18 of the Indenture is hereby eliminated in its entirety
and replaced with the words: "Section 4.18. [INTENTIONALLY OMITTED]."

      (17) Section 5.01 of the Indenture is hereby eliminated in its entirety
and replaced with the words: "Section 5.01. [INTENTIONALLY OMITTED]."

      (18) Section 6.01 of the Indenture is hereby amended to delete the text in
subsections 6.01(5) and 6.01(6) and 6.01(7) and to replace the text thereof with
the text "[INTENTIONALLY OMITTED]."

      (19) Section 8.04 of the Indenture is hereby eliminated in its entirety
and replaced with the words: "Section 8.04. [INTENTIONALLY OMITTED]."

      (20) Section 11.05 of the Indenture is hereby eliminated in its entirety
and replaced with the words: "Section 11.05. [INTENTIONALLY OMITTED]."

      SECTION 3. EFFECTIVENESS. This Second Supplemental Indenture supplements
the Indenture with respect to the Notes and shall be a part and subject to all
of the terms thereof. Except as supplemented hereby, the Indenture shall
continue in full force and effect.

      The Amendments effected by this Second Supplemental Indenture shall take
effect on the date that each of the following conditions shall have been
satisfied or waived:

      (a) each of the parties hereto shall have executed and delivered this
      Second Supplemental Indenture; and

      (b) The Company shall have received written consent to these Amendments
      from the Holders of at least a majority in principal amount of the Notes;

provided, however, that the Amendments set forth in Section 2 of this Second
Supplemental Indenture shall become operative only upon and simultaneously with,
and shall have no force and effect prior to, the Company's acceptance for
purchase of and payment for the Notes that are tendered and not withdrawn
pursuant to the Tender Offer.

      SECTION 4. NEW YORK LAW TO GOVERN. THE INTERNAL LAW OF THE STATE OF NEW
YORK SHALL GOVERN AND BE USED TO CONSTRUE THIS SECOND SUPPLEMENTAL INDENTURE TO
THE EXTENT THAT THE APPLICATION OF THE LAWS OF ANOTHER JURISDICTION WOULD BE
REQUIRED THEREBY.

      SECTION 5. COUNTERPARTS. The parties may sign any number of copies of this
Second Supplemental Indenture. Each signed copy shall be an original, but all of
them together represent the same agreement.

      SECTION 6. EFFECT OF HEADINGS. The Section headings herein are for
convenience only and shall not affect the construction hereof.



<PAGE>

      SECTION 7. THE TRUSTEE. The Trustee accepts the amendment to the Indenture
effected by this Second Supplemental Indenture. Without limiting the generality
of the foregoing, the Trustee has no responsibility for the correctness of the
recitals of fact herein contained which shall be taken as the statements of the
Guarantors and the Company and makes no representations as to the validity or
sufficiency of this Second Supplemental Indenture, except as to the due and
valid execution hereof by the Trustee, and shall incur no liability or
responsibility in respect of the validity thereof.

      SECTION 8. SUBSIDIARY GUARANTEES. Each of the Guarantors hereby affirms
that its Subsidiary Guarantee remains effective in all respects regardless of
the effect of this Second Supplement Indenture on the Indenture.

      SECTION 9. CONFLICT OF ANY PROVISION OF INDENTURE WITH TRUST INDENTURE
ACT. If and to the extent that any provision in this Second Supplemental
Indenture limits, qualifies or conflicts with another provision included in this
Second Supplemental Indenture or in the Indenture which is required to be
included herein or therein by any of TIA Sections 310 to 317, inclusive, such
required provision shall control.

                            [Signature page follows]


<PAGE>


      IN WITNESS WHEREOF, the parties hereto have caused this Second
Supplemental Indenture to be duly executed of the date first above written.

                                            THE SCOTTS COMPANY


                                            By: /s/ Christopher Nagel
                                                --------------------------------
                                            Name: Christopher Nagel
                                            Title: Chief Financial Officer

                                            GUARANTORS:


                                            SCOTTS MANUFACTURING COMPANY, as
                                            successor by merger to SCOTTS
                                            MIRACLE-GRO PRODUCTS INC.


                                            By: /s/ Christopher Nagel
                                                --------------------------------
                                            Name: Christopher Nagel
                                            Title: Chief Financial Officer

                                            SCOTTS TEMECULA OPERATIONS, LLC,
                                            as successor by merger to
                                            REPUBLIC TOOL & MANUFACTURING CORP.

                                            By: /s/ Christopher Nagel
                                                --------------------------------
                                            Name: Christopher Nagel
                                            Title: Chief Financial Officer

                                            MIRACLE-GRO LAWN PRODUCTS, INC.


                                            By: /s/ Christopher Nagel
                                                --------------------------------
                                            Name: Christopher Nagel
                                            Title: Chief Financial Officer

                                            OMS INVESTMENTS, INC.


                                            By: /s/ Christopher Nagel
                                                --------------------------------
                                            Name: Christopher Nagel
                                            Title: Chief Financial Officer


<PAGE>

                                            HYPONEX CORPORATION


                                            By: /s/ Christopher Nagel
                                                --------------------------------
                                            Name: Christopher Nagel
                                            Title: Chief Financial Officer

                                            SCOTTS PRODUCTS CO.


                                            By: /s/ Christopher Nagel
                                                --------------------------------
                                            Name: Christopher Nagel
                                            Title: Chief Financial Officer

                                            SCOTTS PROFESSIONAL PRODUCTS CO.


                                            By: /s/ Christopher Nagel
                                                --------------------------------
                                            Name: Christopher Nagel
                                            Title: Chief Financial Officer

                                            SCOTTS-SIERRA HORTICULTURAL
                                            PRODUCTS COMPANY


                                            By: /s/ Christopher Nagel
                                                --------------------------------
                                            Name: Christopher Nagel
                                            Title: Chief Financial Officer

                                            SCOTTS-SIERRA CROP PROTECTION
                                            COMPANY


                                            By: /s/ Christopher Nagel
                                                --------------------------------
                                            Name: Christopher Nagel
                                            Title: Chief Financial Officer

                                            SCOTTS-SIERRA INVESTMENTS, INC.


                                            By: /s/ Christopher Nagel
                                                --------------------------------
                                            Name: Christopher Nagel
                                            Title: Chief Financial Officer

                                            SWISS FARMS PRODUCTS, INC.


                                            By: /s/ Christopher Nagel
                                                --------------------------------
                                            Name: Christopher Nagel
                                            Title: Chief Financial Officer


<PAGE>


U.S. BANK NATIONAL ASSOCIATION,
As Trustee

By: /s/ Cauna M. Silva
    ---------------------------
Name: Cauna M. Silva
Title:   Vice President