<PAGE>
 
                           HINES HORTICULTURE, INC.

                     FOURTH AMENDMENT, CONSENT AND WAIVER
                              TO CREDIT AGREEMENT


         This FOURTH AMENDMENT, CONSENT AND WAIVER TO CREDIT AGREEMENT (this
"AMENDMENT") is dated as of August 28, 1996 and entered into by and among HINES
HORTICULTURE, INC. (formerly known as Hines Nurseries Inc.), a California
corporation ("COMPANY"), SUN GRO HORTICULTURE INC., a Nevada corporation ("SUN
GRO"), and SUN GRO HORTICULTURE CANADA LTD., a Canadian corporation ("SUN GRO
CANADA"; together with Company and Sun Gro, collectively, "BORROWERS"), the
financial institutions listed on the signature pages hereof ("LENDERS") and BT
COMMERCIAL CORPORATION, as Agent for Lenders ("AGENT"), and, for purposes of
Section 6 hereof, the Credit Support Parties (as defined in Section 6 hereof)
listed on the signature pages hereof, and is made with reference to that certain
Credit Agreement dated as of August 4, 1995 by and among Company, Sun Gro and
Sun Gro Canada, Lenders and Agent, as amended by that certain First Amendment
dated as of October 11, 1995, that certain Second Amendment dated as of October
26, 1995, and that certain Third Amendment dated as of March 15, 1996 (as so
amended, the "CREDIT AGREEMENT").  Capitalized terms used herein without
definition shall have the same meanings herein as set forth in the Credit
Agreement.


                                    RECITALS

         WHEREAS, Company has requested Lenders to consent to the acquisition of
the assets of Iverson Perennial Gardens, Inc. and certain related real property;
and Lenders are willing, subject to the terms and conditions set forth herein,
to further waive Company's compliance with clause (ii) of the last proviso in
subsection 7.8 of the Credit Agreement; and

         WHEREAS, Borrowers and Lenders desire to amend the Credit Agreement to
(i) adjust certain of the covenants set forth therein, (ii) agree as to certain
matters relating to certain equity contributions to be made by MDCP, and (iii)
make certain other amendments as set forth below:

         NOW, THEREFORE, in consideration of the premises and the agreements,
provisions and covenants herein contained, the parties hereto agree as follows:
 
                                       1
<PAGE>
 
         SECTION 1.  AMENDMENTS TO THE CREDIT AGREEMENT
 
         1.1  AMENDMENTS TO SECTION 1: PROVISIONS RELATING TO DEFINED TERMS
              -------------------------------------------------------------

         A.   Subsection 1.1 of the Credit Agreement is hereby amended by adding
thereto the following definitions, which shall be inserted in the proper
alphabetical order:

         "`IPG' means Iverson Perennial Gardens, Inc., a Delaware corporation."

         "`IPG ACQUISITION AGREEMENTS' means, collectively, (i) that certain
    Acquisition  Agreement dated as of August 30, 1996 by and among Ronald C.
    Iverson, IPG and Company, and (ii) that certain Consulting and Non-
    Competition Agreement dated as of August 30, 1996 by and between Ronald
    Iverson and Company."

         "`IVERSON ACQUISITION' means the acquisition by Company of the Iverson
    Properties pursuant to IPG Acquisition Agreements."

         "`IVERSON PROPERTIES' means (i) all of the operating assets of IPG's
    South Carolina nursery operations (including without limitation related
    Inventory located outside of South Carolina), and (ii) approximately 527
    acres of real property owned by Ronald C. Iverson in South Carolina relating
    to and used by IPG in its nursery operations."


         1.2  AMENDMENTS TO SECTION 2: AMOUNTS AND TERMS OF COMMITMENTS AND
              -------------------------------------------------------------
              LOANS
              -----

         USE OF PROCEEDS: REVOLVING LOANS.  Section 2.5B of the Credit Agreement
is hereby amended by deleting the second sentence contained therein in its
entirety and substituting the following therefor:

              "Any excess proceeds of the initial Revolving Loans and the
         proceeds of any subsequent Revolving Loans shall be applied by Company
         and Sun Gro for (i) working capital and general corporate purposes,
         which may include the making of intercompany loans to any of Company's
         wholly-owned Subsidiaries, in accordance with subsection 7.1(iv), for
         their own working capital and general corporate purposes, and (ii)
         consummation of the Iverson Acquisition, so long as the aggregate
         amount of Revolving Loans applied to consummate such Iverson
         Acquisition (including all fees and expenses relating thereto) does not
         exceed $10,400,000."
 

                                       2
<PAGE>
 
         1.3  AMENDMENTS TO SECTION 5: BORROWERS' REPRESENTATIONS AND WARRANTIES
              ------------------------------------------------------------------

         MATERIAL CONTRACTS.  Subsection 5.8C of the Credit Agreement is hereby
amended by deleting the second sentence contained therein in its entirety and
substituting the following therefor:

              "Except as described on Schedule 5.8C, all such Material Contracts
         (other than any Material Contract which has been terminated as
         permitted under the Loan Documents and which termination has been
         reported to Lenders in accordance with subsection 6.1(xviii)) are in
         full force and effect and no material defaults currently exist
         thereunder."


         1.4  AMENDMENTS TO SECTION 6: BORROWERS' AFFIRMATIVE COVENANTS
              ---------------------------------------------------------

         ADDITIONAL MORTGAGES.  Subsection 6.12 of the Credit Agreement is
hereby amended by inserting immediately after the reference to "as soon as
practicable after the acquisition of such Covered Real Property Asset" contained
in clause (ii) therein the following:

              "(and in the case of any Covered Real Property Asset acquired in
         connection with the Iverson Acquisition, as soon as practicable after
         the consummation of the Iverson Acquisition but in any event within
         forty-five days after the effective date of the Fourth Amendment,
         Consent and Waiver to Credit Agreement dated as of August 28, 1996 by
         and among Company, Sun Gro, Sun Gro Canada, Lenders and Agent)".


         1.5  AMENDMENTS TO SECTION 7: BORROWERS' NEGATIVE COVENANTS
              ------------------------------------------------------

         CONSOLIDATED CAPITAL EXPENDITURES.  Subsection 7.8 of the Credit
Agreement is hereby amended by (a) deleting the reference to "and" and adding
"," at the end of clause (i) of the proviso contained therein, and (b) adding
the following after clause (ii) of the last proviso contained therein, but
before the last period:

              "and (iii) Company may incur additional Consolidated Capital
         Expenditures on or before September 20, 1996 in an aggregate amount
         (including all fees and expenses relating thereto) not to exceed the
         sum of (x) $10,400,000 plus (y) the assumption of unsecured Assumed
         Liabilities (as defined in the acquisition agreement described in
         clause (i) of the definition "IPG Acquisition Agreements") not to
         exceed $1,000,000, consisting of the Iverson Acquisition".

                                       3
<PAGE>
 
         1.6  AMENDMENTS TO SECTION 8: EVENTS OF DEFAULT
              ------------------------------------------

         A.   CONDUCT OF BUSINESS RELATING TO HOLDINGS.  Subsection 8.18 of the
Credit Agreement is hereby amended by deleting the reference to ":" at the end
of such subsection and substituting "; or" therefor.

         B.   IVERSON ACQUISITION EQUITY CONTRIBUTIONS.  Section 8 of the Credit
Agreement is hereby amended by adding as a new subsection 8.19 the following:

         "8.19  EQUITY CONTRIBUTIONS.
                -------------------- 

                   (i) Holdings shall not have received from MDCP on or prior to
         October 15, 1996 an equity contribution in an amount not less than
         $10,000,000 but not greater than $20,000,000 (the "PARENT EQUITY
         CONTRIBUTION"); or (ii) Company shall not have received from Holdings
         on or prior to October 15, 1996 an equity contribution in an amount
         equal to the Parent Equity Contribution; or (iii) Company shall not
         have used the proceeds from the Parent Equity Contribution within one
         Business Day of receipt of such proceeds (x) to prepay all Revolving
         Loans of Company and of Sun Gro on a pro rata basis (in accordance with
         the respective outstanding principal amount thereof) without any
         corresponding reduction in their respective Revolving Loan Commitments,
         and (y) to the extent the amount of such proceeds exceed the aggregate
         outstanding principal amount of Revolving Loans, to prepay all Term
         Loans in accordance to the application order set forth in the first
         sentence of subsection 2.4B(iv)(b) in an amount equal to such excess
         (it being understood by all parties hereto that Company shall apply the
         proceeds from the Parent Equity Contribution in the manner set forth in
         this clause (iii) of this subsection 8.19 notwithstanding anything to
         the contrary contained in subsection 2.4B(iii)(c) or 2.4B(iv)(b)):"


         SECTION 2.  AMENDMENTS TO THE SECURITY AGREEMENT

         2.1  MODIFICATIONS OF SCHEDULE I TO THE SECURITY AGREEMENT
              -----------------------------------------------------

         SCHEDULE I: SUPPLEMENTAL DESCRIPTIONS OF COLLATERAL.  Schedule I to the
Security Agreement, as amended, is hereby amended by adding thereto the items
set forth in Annex A attached hereto.

         2.2  MODIFICATIONS OF SCHEDULE II TO THE SECURITY AGREEMENT
              ------------------------------------------------------

         SCHEDULE II: LOCATION OF COLLATERAL.  Schedule II to the Security
Agreement, as amended, is hereby amended by adding thereto the items set forth
in Annex B attached hereto.

                                       4
<PAGE>
 
         2.3  MODIFICATIONS OF SCHEDULE III TO THE SECURITY AGREEMENT
              -------------------------------------------------------

         SCHEDULE III: EXISTING FINANCING STATEMENTS.  Schedule III to the
Security Agreement, as amended, is hereby amended by adding thereto the items
set forth in Annex C attached hereto.

 
         SECTION 3.  CONSENT AND WAIVER

         3.1  CONSENT TO IVERSON ACQUISITION AND WAIVER OF CERTAIN COVENANTS
              --------------------------------------------------------------

         Subject to the terms and conditions set forth herein and in reliance on
the representations and warranties of Company contained herein, Lenders hereby:

         1.  consent to the Iverson Acquisition by Company for a total
    consideration (including all fees and expenses relating thereto) not
    exceeding the sum of (x) $10,400,000 plus (y) the assumption of unsecured
    Assumed Liabilities (as defined in the acquisition agreement described in
    clause (i) of the definition "IPG Acquisition Agreements") not to exceed
    $1,000,000; and

         2.  waive compliance with the provisions of clause (ii) of the last
    proviso in subsection 7.8 of the Credit Agreement to the extent, and only to
    the extent, necessary to permit Company to incur (a) $1,250,000 of the
    additional Consolidated Capital Expenditures permitted under such clause
    (ii) on or before July 6, 1996 and (b) $100,000 of the additional
    Consolidated Capital Expenditures permitted under such clause (ii) on or
    before December 31, 1996.


         3.2  LIMITATION OF CONSENT AND WAIVER
              --------------------------------

         Without limiting the generality of the provisions of subsection 10.6 of
the Credit Agreement, both the consent and waiver set forth above shall be
limited precisely as written and relate solely to the Iverson Acquisition and
the noncompliance of Company with the provisions of clause (ii) of the last
proviso in subsection 7.8 of the Credit Agreement in the manner and to the
extent described above, and nothing in this Section 3 shall be deemed to:

         1.  constitute a waiver of compliance by Company with respect to (a)
    clause (ii) of the last proviso in subsection 7.8 of the Credit Agreement in
    any other instance or (b) any other term, provision or condition of the
    Credit Agreement or any other instrument or agreement referred to therein
    (whether in connection with the Iverson Acquisition or waiver of clause (ii)
    of the last proviso in subsection 7.8 of the Credit Agreement or otherwise);
    or

                                       5
<PAGE>
 
         2. prejudice any right or remedy that Agent or any Lender may now have
    (except to the extent that such right or remedy was based upon existing
    defaults that will not exist after giving effect to this Section 3) or may
    have in the future under or in connection with the Credit Agreement or any
    other instrument or agreement referred to therein.

         Except as expressly set forth herein, the terms, provisions and
conditions of the Credit Agreement and the other Loan Documents shall remain in
full force and effect and in all other respects are hereby ratified and
confirmed.


         SECTION 4.  CONDITIONS TO EFFECTIVENESS

         Sections 1, 2 and 3 of this Amendment shall become effective only upon
the satisfaction of all of the following conditions precedent (the date of
satisfaction of such conditions being referred to herein as the "FOURTH
AMENDMENT EFFECTIVE DATE"):

         A.   On or before the Fourth Amendment Effective Date, Holdings and
each Borrower shall deliver to Lenders (or to Agent for Lenders with sufficient
originally executed copies, where appropriate, for each Lender and its counsel)
the following, each, unless otherwise noted, dated the Fourth Amendment
Effective Date:

              1.  Certificate of the corporate secretary or assistant secretary
    for each of Holdings and each Borrower certifying as of the Fourth Amendment
    Effective Date that:

                   a.  The Certificate or Articles of Incorporation of Holdings
         or such Borrower have not been amended, modified or otherwise changed
         since the Closing Date; and

                   b.  The Bylaws of Holdings or such Borrower have not been
         amended, modified or otherwise changed since the Closing Date;

              2.  Resolutions of Board of Directors of each of Holdings and each
    Borrower approving and authorizing the execution, delivery, and performance
    of this Amendment, certified as of the Fourth Amendment Effective Date by
    Holdings or such Borrower's corporate secretary or an assistant secretary as
    being in full force and effect without modification or amendment;

              3.  Signature and incumbency certificates of officers of each of
    Holdings and each Borrower executing this Amendment;

              4.  Executed copies of the IPG Acquisition Agreements, each in
    form and substance satisfactory to Agent;

                                       6
<PAGE>
 
              5. Uniform Commercial Code ("UCC") searches relating to the
    Iverson Properties in form and substance satisfactory to Agent;

              6.  UCC-1 financing statements, executed by the Company, relating
    to the Iverson Properties for all jurisdictions as may be necessary or
    desirable to perfect the security interests in the Iverson Properties in
    form and substance satisfactory to Agent;

              7.  UCC-3 termination statements, mortgage releases or other
    comparable instruments, executed by all necessary Persons, terminating any
    and all existing UCC-1 financing statements or mortgages relating to the
    Iverson Properties in favor of any third parties (other than UCC-1 financing
    statements filed pursuant to item 6 above) in form and substance
    satisfactory to Agent;

              8.  Evidence in form and substance satisfactory to Agent
    (including without limitation an Officers' Certificate to the effect set
    forth in clauses (i) - (iv) below) that:

              (i) the IPG Acquisition Agreements shall be in full force and
         effect and shall not have been amended, supplemented, waived or
         otherwise modified without the consent of Agent;

              (ii) all conditions to the Iverson Acquisition set forth in the
         IPG Acquisition Agreements shall have been satisfied in all material
         respects or the fulfillment of any such conditions shall have been
         waived with the consent of Agent (which consent shall not be
         unreasonably withheld);

              (iii)  the Iverson Acquisition shall have occurred; and

              (iv) the aggregate purchase price for the Iverson Acquisition
         (including all fees and expenses relating thereto) does not exceed the
         sum of (x) $10,400,000 plus (y) the assumption of unsecured Assumed
         Liabilities (as defined in the acquisition agreement described in
         clause (i) of the definition "IPG Acquisition Agreements") not to
         exceed $1,000,000;

              9.  Pro forma balance sheet of Company and its Subsidiaries as of
    August 31, 1996 after giving effect to the Iverson Acquisition and the
    financings contemplated thereby, and projected financial statements
    (including balance sheets and statements of operations, stockholders' equity
    and cash flows) of Company and its Subsidiaries for the five-year period
    after consummation of the Iverson Acquisition, all of the foregoing in form
    and substance satisfactory to Agent and Lenders;

                                       7
<PAGE>
 
              10. Any and all environmental reports relating to the Iverson
    Properties received by Company from IPG or obtained by Company or any of its
    Subsidiaries from any independent consultants; and

              11. Copies of this Amendment executed by Holdings, each Borrower,
    Requisite Lenders and Requisite Class Lenders of each Class.

         B.   On or before the Fourth Amendment Effective Date, all corporate
and other proceedings taken or required to be taken in connection with the
transactions contemplated hereby and all documents incidental thereto not
previously found acceptable by Agent, acting on behalf of Lenders, and its
counsel shall be satisfactory in form and substance to Agent and such counsel,
and Agent and such counsel shall have received all such counterpart originals or
certified copies of such documents as Agent may reasonably request.


         SECTION 5.  BORROWER'S REPRESENTATIONS AND WARRANTIES

         In order to induce Lenders to enter into this Amendment and to amend
the Credit Agreement in the manner provided herein, each Borrower represents and
warrants to each Lender that the following statements are true, correct and
complete:

         A.   CORPORATE POWER AND AUTHORITY.  Each Loan Party has all requisite
corporate power and authority to enter into this Amendment and to carry out the
transactions contemplated by, and perform its obligations under, the Credit
Agreement as amended by this Amendment (the "AMENDED AGREEMENT").

         B.   AUTHORIZATION OF AGREEMENTS.  The execution and delivery of this
Amendment and the performance of the Amended Agreement have been duly authorized
by all necessary corporate action on the part of each Loan Party party hereto.

         C.   NO CONFLICT.  The execution and delivery by each Loan Party of
this Amendment and the performance by each Loan Party hereto of the Amended
Agreement do not and will not (i) violate any provision of any law or any
governmental rule or regulation applicable to Holdings or any of its
Subsidiaries, the Certificate or Articles of Incorporation or Bylaws of Holdings
or any of its Subsidiaries or any order, judgment or decree of any court or
other agency of government binding on Holdings or any of its Subsidiaries, (ii)
conflict with, result in a breach of or constitute (with due notice or lapse of
time or both) a default under any Contractual Obligation of Holdings or any of
its Subsidiaries, (iii) result in or require the creation or imposition of any
Lien upon any of the properties or assets of Holdings or any of its Subsidiaries
(other than Liens created under any of the Loan Documents in favor of Agent on
behalf of Lenders), or (iv) require any approval of stockholders or any approval
or consent of any Person under any Contractual Obligation of Holdings or any of
its Subsidiaries, except for such

                                       8
<PAGE>
 
approvals or consents which have been obtained on or before the Fourth Amendment
Effective Date and disclosed in writing to Lenders.

         D.   GOVERNMENTAL CONSENTS.  The execution and delivery by the Loan
Parties hereto of this Amendment and the performance by the Loan Parties hereto
of the Amended Agreement do not and will not require any registration with,
consent or approval of, or notice to, or other action to, with or by, any
federal, state or other governmental authority or regulatory body.

         E.   BINDING OBLIGATION.  This Amendment has been duly executed and
delivered by each Loan Party and this Amendment and the Amended Agreement are
the legally valid and binding obligations of such Loan Party, enforceable
against such Loan Party in accordance with their respective terms, except as may
be limited by bankruptcy, insolvency, reorganization, moratorium or similar laws
relating to or limiting creditors' rights generally or by equitable principles
relating to enforceability.

         F.   INCORPORATION OF REPRESENTATIONS AND WARRANTIES FROM CREDIT
AGREEMENT.  The representations and warranties contained in Section 5 of the
Credit Agreement and contained in the other Loan Documents are and will be true,
correct and complete in all material respects on and as of the Fourth Amendment
Effective Date to the same extent as though made on and as of that date, except
to the extent such representations and warranties specifically relate to an
earlier date, in which case they were true, correct and complete in all material
respects on and as of such earlier date.

         G.   ABSENCE OF DEFAULT.  No event has occurred and is continuing or
will result from the consummation of the transactions contemplated by this
Amendment that would constitute an Event of Default or a Potential Event of
Default.  Agent and Lenders acknowledge that Borrowers have notified Agent and
Lenders that Borrowers may be unable to be in compliance with certain financial
covenants contained in subsection 7.6 of the Credit Agreement at the end of the
Fiscal Quarter ending on September 30, 1996.  Each party hereto agrees that
neither such notice nor such acknowledgement by Agent and Lenders in any way
constitutes a waiver of compliance by Borrowers with respect to subsection 7.6
of the Credit Agreement in any instance or at any time (including without
limitation at the end of the Fiscal Quarter ending on September 30, 1996), any
Event of Default or Potential Event of Default, or any other term or provision
of any Loan Document or prejudices any right or remedy that Agent or any Lender
may now have or may have in the future under or in connection with any Loan
Document.


         SECTION 6.  ACKNOWLEDGEMENT AND CONSENT

         Company is a party to the Company Guaranty, the Company Security
Agreement, the Company Pledge Agreement, the Company Trademark Security
Agreement, the Company Patent Security Agreement and the Collateral Account

                                       9
<PAGE>
 
Agreement pursuant to which Company has (i) guarantied the Obligations and (ii)
created liens in favor of Agent on certain Collateral to secure the Obligations
and to secure its obligations under the Company Guaranty.  Sun Gro is a party to
the Domestic Subsidiary Guaranty, the Domestic Subsidiary Security Agreement,
the Domestic Subsidiary Pledge Agreement, the Domestic Subsidiary Trademark
Security Agreement, the Domestic Subsidiary Patent Security Agreement and the
Collateral Account Agreement pursuant to which Sun Gro has (i) guarantied the
Obligations and (ii) created liens in favor of Agent on certain Collateral to
secure the obligations of Sun Gro under the Domestic Subsidiary Guaranty.  Sun
Gro Canada is a party to the Canadian Subsidiary Security Agreement and the
Canadian Subsidiary Pledge Agreement pursuant to which Sun Gro Canada has
created liens in favor of Agent on certain Collateral to secure certain of the
Obligations.  Holdings is a party to the Holdings Guaranty and the Holdings
Pledge Agreement pursuant to which Holdings has (i) guarantied the Obligations
and (ii) pledged certain Collateral to Agent to secure the obligations of
Holdings under the Holdings Guaranty.  Company, Sun Gro, Sun Gro Canada and
Holdings are collectively referred to herein as the "CREDIT SUPPORT PARTIES",
and the Guaranties and Collateral Documents referred to above are collectively
referred to herein as the "CREDIT SUPPORT DOCUMENTS".

          Each Credit Support Party hereby acknowledges that it has reviewed the
terms and provisions of the Credit Agreement and this Amendment and consents to
the amendment of the Credit Agreement effected pursuant to this Amendment.  Each
Credit Support Party hereby confirms that each Credit Support Document to which
it is a party or otherwise bound and all Collateral encumbered thereby will
continue to guaranty or secure, as the case may be, to the fullest extent
possible the payment and performance of all "Obligations," "Guarantied
Obligations" and "Secured Obligations," as the case may be (in each case as such
terms are defined in the applicable Credit Support Document), including without
limitation the payment and performance of all such "Obligations," "Guarantied
Obligations" or "Secured Obligations," as the case may be, in respect of the
Obligations of Borrowers now or hereafter existing under or in respect of the
Amended Agreement and the Notes defined therein.

          Each Credit Support Party acknowledges and agrees that any of the
Credit Support Documents to which it is a party or otherwise bound shall
continue in full force and effect and that all of its obligations thereunder
shall be valid and enforceable and shall not be impaired or limited by the
execution or effectiveness of this Amendment.  Each Credit Support Party
represents and warrants that all representations and warranties contained in the
Amended Agreement and the Credit Support Documents, in each case to which it is
a party or otherwise bound, are true, correct and complete in all material
respects on and as of the Fourth Amendment Effective Date to the same extent as
though made on and as of that date, except to the extent such representations
and warranties specifically relate to an earlier date, in which case they were
true, correct and complete in all material respects on and as of such earlier
date.

                                       10
<PAGE>
 
          Each Credit Support Party (other than Borrowers) acknowledges and
agrees that (i) notwithstanding the conditions to effectiveness set forth in
this Amendment, such Credit Support Party is not required by the terms of the
Credit Agreement or any other Loan Document to consent to the amendments to the
Credit Agreement effected pursuant to this Amendment and (ii) nothing in the
Credit Agreement, this Amendment or any other Loan Document shall be deemed to
require the consent of such Credit Support Party to any future amendments to the
Credit Agreement.


          SECTION 7.  MISCELLANEOUS

          A.   REFERENCE TO AND EFFECT ON THE CREDIT AGREEMENT AND THE OTHER
LOAN DOCUMENTS.

          (i) On and after the Fourth Amendment Effective Date, each reference
    in the Credit Agreement to "this Agreement", "hereunder", "hereof", "herein"
    or words of like import referring to the Credit Agreement, and each
    reference in the other Loan Documents to the "Credit Agreement",
    "thereunder", "thereof" or words of like import referring to the Credit
    Agreement shall mean and be a reference to the Amended Agreement.

          (ii) Except as specifically amended by this Amendment, the Credit
    Agreement and the other Loan Documents shall remain in full force and effect
    and are hereby ratified and confirmed.

          (iii)  The execution, delivery and performance of this Amendment shall
    not, except as expressly provided herein, constitute a waiver of any
    provision of, or operate as a waiver of any right, power or remedy of Agent
    or any Lender under, the Credit Agreement or any of the other Loan
    Documents.

          B.   FEES AND EXPENSES.  Company acknowledges that all costs, fees and
expenses as described in subsection 10.2 of the Credit Agreement incurred by
Agent and its counsel with respect to this Amendment and the documents and
transactions contemplated hereby shall be for the account of Company.

          C.   HEADINGS.  Section and subsection headings in this Amendment are
included herein for convenience of reference only and shall not constitute a
part of this Amendment for any other purpose or be given any substantive effect.

          D.   APPLICABLE LAW.  THIS AMENDMENT AND THE RIGHTS AND OBLIGATIONS OF
THE PARTIES HEREUNDER SHALL BE GOVERNED BY, AND SHALL BE CONSTRUED AND ENFORCED
IN ACCORDANCE WITH, THE INTERNAL LAWS OF THE STATE OF NEW YORK (INCLUDING
WITHOUT LIMITATION SECTION 5-1401 OF THE GENERAL OBLIGATIONS LAW OF THE

                                       11
<PAGE>
 
STATE OF NEW YORK), WITHOUT REGARD TO CONFLICTS OF LAWS PRINCIPLES.

          E.   COUNTERPARTS; EFFECTIVENESS.  This Amendment may be executed in
any number of counterparts and by different parties hereto in separate
counterparts, each of which when so executed and delivered shall be deemed an
original, but all such counterparts together shall constitute but one and the
same instrument; signature pages may be detached from multiple separate
counterparts and attached to a single counterpart so that all signature pages
are physically attached to the same document.  This Amendment (other than the
provisions of Sections 1, 2 and 3 hereof, the effectiveness of which is governed
by Section 4 hereof) shall become effective upon the execution of a counterpart
hereof by Requisite Lenders, Holdings and each Borrower and receipt by Company
and Agent of written or telephonic notification of such execution and
authorization of delivery thereof.



                  [Remainder of page intentionally left blank]

                                       12
<PAGE>
 
                                    ANNEX A
                                    -------

                    Supplemental Descriptions of Collateral
                    ---------------------------------------


Specific Inventory Included in Collateral:
----------------------------------------- 

    Growing plants in containers, clumps, potting machines, irrigation
    equipment, conveyors, related production tools, office equipment, office and
    warehouse buildings located on premises, land as described in Appendix A
    attached hereto.


Material Assigned Agreements:
---------------------------- 

         1.   Lease of 60 acres from the Blocker Family, dated July 25, 1991.

         2.   Supply contracts over $50,000:
<TABLE>
<CAPTION>
 
            VENDOR                 PURCHASES       TERMS
<S>                              <C>            <C>
1.  Thomas Transport             $1,378,188.45     Net 30
2.  Vaughan's Seed Company       $  435,262.50    Net 120
3.  V-J Growers Supply           $  237,924.17     Net 90
4.  Witteman & Co.               $  227,326.90  1% 10 Net 30
5.  John Henry                   $  223,533.16     Net 30
6.  Jac. TH DE Vroomen Inc.      $  159,716.33     Net 30
7.  Guernsey Clematis Nursery    $  147,735.65     Net 30
8.  Nursery Supplies, Inc.       $  134,982.08    Net 120
9.  Poppelmann                   $   91,587.52     Net 60
10. Cannon Equipment Co.         $   61,563.37     Net 30
11. Oosterwijck                  $   53,379.81     Net 30
12. Summit Plastic Co.           $   49,144.61     Net 90
 
</TABLE>
         3.   Purchase Orders.  See Appendix B attached hereto.
                                    ----------                 

         4.   Agreement with John Deere relating to the financing of four John
              Deere Tractors (unpaid balance is $54,822)


                                   Annex A-1
<PAGE>

Specific Varieties and Types of Crops Included in Collateral:
------------------------------------------------------------- 

               Hosta, Hemcucallis, Perennials

<TABLE>
<CAPTION>

Trademark Registrations:
--------------------------

Trademark                    Registration No.        Country
---------                    ----------------        -------
<S>                          <C>                     <C> 
Iverson                      1418582                 USA
Signature Series             1418580                 USA
Butterfly Blue               2437622                 USA
IAM                          1928509                 USA
Iverson                      1697877                 USA
Plant Talker                 1736469                 USA
Signature Collection         1718328                 USA
Signature Series             1575370                 USA
 

Patent Registrations:
--------------------- 

Patent No.                   Country
----------                   -------
Des. 322,707                 USA
Des. 323,416                 USA
Des. 323,415                 USA
Plant Pat. 8,140             USA
Plant Pat. 8,801             USA
Plant Pat. 9,380             USA
Plant Pat. 9,386             USA
Plant Pat. 9,387             USA
Plant Pat. 9,372             USA

</TABLE> 


                                   Annex A-2

<PAGE>
 
                                    ANNEX B
                                    -------

                            Location of Collateral
                            ----------------------


Filing Jurisdictions:
--------------------- 

     South Carolina, Secretary of State
     South Carolina, Edgefield County
     Illinois, Secretary of State



Locations of Equipment, Inventory, Crops and Farm Products:
----------------------------------------------------------- 

The nursery located at the following address:

     Iverson Perennials
     Route 1
     Highway 25
     Trenton, South Carolina 29847

situated on land owned of record by Hines Horticulture, Inc. and described more
fully as set forth on Appendix A attached hereto.



The nursery located at the following address:

     Iverson Perennial Gardens
     2787 RFD
     Long Grove, Illinois 60047



                                   Annex B-1

<PAGE>
 
                                    ANNEX C
                                    -------

                         Existing Financing Statements
                         -----------------------------


No additional financing statements.




                                   Annex C-1

<PAGE>
 
         IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
duly executed and delivered by their respective officers thereunto duly
authorized as of the date first written above.

                               HINES HORTICULTURE, INC. (formerly           
                               known as Hines Nurseries Inc.),
                               as Borrower


                               By: _______________________________
                               Title: ____________________________



                               SUN GRO HORTICULTURE INC.,
                               as Borrower


                               By: _______________________________
                               Title: ____________________________



                               SUN GRO HORTICULTURE CANADA LTD.,
                               as Borrower


                               By: _______________________________
                               Title: ____________________________



                               HINES HOLDINGS, INC., (formerly known
                               as Hines Horticulture Inc.)(for purposes
                               of Section 6 only) as a Credit Support Party


                               By: _______________________________
                               Title: ____________________________





                                      S-1
<PAGE>
 
                               BT COMMERCIAL CORPORATION,
                               AS A DOMESTIC LENDER AND AS AGENT


                               By: ________________________________
                               Title: _____________________________



                               BT BANK OF CANADA,
                               as a Canadian Lender


                               By: _______________________________
                               Title: ____________________________



                               BANKERS TRUST COMPANY,
                               as an Issuing Lender


                               By: _______________________________
                               Title: ____________________________









                                      S-2
<PAGE>
 
                               HARRIS TRUST AND SAVINGS BANK,
                               as a Domestic Lender


                               By: _______________________________
                               Title: ____________________________



                               FLEET BANK OF MASSACHUSETTS, N.A., 
                               as a Domestic Lender


                               By: _______________________________
                               Title: ____________________________



                               LASALLE NATIONAL BANK,
                               as a Domestic Lender


                               By: _______________________________
                               Title: ____________________________



                               NATIONSBANK OF TEXAS, N.A.,
                               as a Domestic Lender and Canadian Lender


                               By: _______________________________
                               Title: ____________________________



                               UNION BANK OF CALIFORNIA, N.A.
                               as a Domestic Lender and Canadian Lender


                               By: _______________________________
                               Title: ____________________________







                                      S-3
<PAGE>
 
                               WELLS FARGO BANK, N.A.
                               as a Domestic Lender and Canadian Lender


                               By: _______________________________
                               Title: ____________________________



                               BANK OF MONTREAL,
                               as a Canadian Lender


                               By: _______________________________
                               Title: ____________________________









                                      S-4