Deltic Timber Corporation (NYSE:DEL) Files An 8-K Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers
Item 5.02. Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

On February 6, 2018, the Executive Compensation Committee (the “Committee”) of the Board of Deltic Timber Corporation (“Deltic”) approved annual measures relating to the compensation of its senior officers, including its named executive officers. The Committee approved (i) annual base salary increases and (ii) an annual grant of restricted stock awards.

On October 22, 2017, Deltic entered into an Agreement and Plan of Merger with Potlatch Corporation (“Potlatch”) and Portland Merger LLC (“Merger Sub”), to which, and subject to shareholder approvals and the satisfaction of certain other conditions, Deltic is expected to be merged with and into Merger Sub. In connection with the proposed merger, Potlatch filed a registration statement with the Securities and Exchange Commission (“SEC”) on Form S-4, which the SEC declared effective on January 17, 2018, setting forth important information regarding the merger, including information required by Item 402(t) of Regulation S-K regarding certain compensation that will or may be paid or become payable to each of Deltic’s named executive officers that is based on or otherwise relates to the merger. The information provided herein serves as an update to the disclosure provided in the Form S-4, as follows:

On January 19, 2018, we commenced mailing to our stockholders a joint proxy statement/prospectus dated January 18, 2018 (the “joint proxy statement/prospectus”) relating to the special meeting of stockholders of Deltic scheduled to be held at 210 East Elm Street, El Dorado, Arkansas 71730 on February 20, 2018, at 11:00 a.m., local time (the “special meeting”). Deltic has decided to make certain additional disclosures and will be filing supplemental proxy materials relating to the joint proxy statement/prospectus for the special meeting of stockholders of Deltic.

ADDITIONAL INFORMATION

This communication is being made in respect of the proposed merger transaction involving Potlatch and Deltic. This communication does not constitute an offer to sell or the solicitation of an offer to buy any securities or a solicitation of any vote or approval, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of such jurisdiction. In connection with the proposed merger, Potlatch and Deltic have filed relevant materials with the Securities and Exchange Commission (“SEC”), including a registration statement filed by Potlatch on FormS-4(Reg. No. 333-221942), which the SEC has declared effective, that includes a joint proxy statement of Potlatch and Deltic and also constitutes a prospectus of Potlatch, which was first mailed to Potlatch and Deltic stockholders on January 19, 2018. BEFORE MAKING ANY VOTING OR INVESTMENT DECISION, SECURITY HOLDERS OF POTLATCH AND DELTIC ARE URGED TO READ THE DEFINITIVE JOINT PROXY STATEMENT/PROSPECTUS REGARDING THE PROPOSED TRANSACTION AND ANY OTHER RELEVANT DOCUMENTS CAREFULLY IN THEIR ENTIRETY WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATIONABOUT THE PROPOSED TRANSACTION.The joint proxy statement/prospectus, as well as other filings containing information about Potlatch and Deltic are available without charge, at the SEC’s Internet site (http://www.sec.gov). Copies of the joint proxy statement/prospectus and the filings with the SEC that are incorporated by reference in the joint proxy statement/prospectus can also be obtained, without charge, from Potlatch’s website at http://www.Potlatchcorp.com under the Investor Resources tab (in the case of documents filed by Potlatch) and on Deltic’s website at https://www.Deltic.com under the Investor Relations tab (in the case of documents filed by Deltic).

Potlatch and Deltic, and certain of their respective directors, executive officers and other members of management and employees may be deemed to be participants in the solicitation of proxies from the stockholders of Deltic and Potlatch in respect of the proposed merger transaction. Certain information about the directors and executive officers of Potlatch is set forth in its Annual Report on Form10-Kfor the year ended December31, 2016, which was filed with the SEC on February17, 2017, its most recent Quarterly Report on Form10-Qfor the quarter ended September30, 2017, which was filed with the SEC on October24, 2017, its proxy statement for its 2017 annual meeting of stockholders, which was filed with the SEC on April3, 2017 and its Current Reports on Form8-K,which were filed on May1, 2017, May4, 2017, October23, 2017 and December7, 2017. Certain Information about the directors and executive officers of Deltic is set forth in its Annual Report on Form10-Kfor the year ended December31, 2016, which was filed with the SEC on March7, 2017, its most recent Quarterly Report on Form10-Qfor the quarter ended September30, 2017, which was filed with the SEC on November2, 2017, its proxy statement for its 2017 annual meeting of stockholders, which was filed with the SEC on March20, 2017, its supplement to the proxy statement for its 2017 annual meeting of the stockholders, which was filed with the SEC on March30, 2017 and its Current Reports on Form8-K, which were filed with the SEC on February27, 2017, March8, 2017, May2, 2017, September1, 2017, September5, 2017, October23, 2017, November11, 2017 and December21, 2017. Other information regarding the participants in the proxy solicitations and a description of their direct and indirect interests, by security holdings or otherwise, are included in the joint proxy statement/prospectus.

CAUTION ABOUT FORWARD-LOOKING STATEMENTS

This communication contains certain forward-looking information about Potlatch and Deltic that is intended to be covered by the safe harbor for “forward-looking statements” provided by the Private Securities Litigation Reform Act of 1995. All statements other than statements of historical fact are forward-looking statements. In some cases, you can identify forward-looking statements by words such as “may,” “hope,” “will,” “should,” “expect,” “plan,”

“anticipate,” “intend,” “believe,” “estimate,” “predict,” “potential,” “continue,” “could,” “future” or the negative of those terms or other words of similar meaning. These forward-looking statements include, without limitation, statements relating to the terms and closing of the proposed transaction between Potlatch and Deltic, the proposed impact of the merger on Potlatch’s financial results, the estimated distribution of Deltic’s accumulated earnings and profits, and the integration of Deltic’s operations. You should carefully read forward-looking statements, including statements that contain these words, because they discuss the future expectations or state other “forward-looking” information about Potlatch and Deltic. A number of important factors could cause actual results or events to differ materially from those indicated by such forward-looking statements, many of which are beyond the parties’ control, including the parties’ ability to consummate the transaction or satisfy the conditions to the completion of the transaction, including the receipt of stockholder approvals; the parties’ ability to meet expectations regarding the timing, completion and accounting and tax treatments of the transaction; the possibility that any of the anticipated benefits of the proposed merger will not be realized or will not be realized within the expected time period; the risk that integration of Deltic’s operations with those of Potlatch will be materially delayed or will be more costly or difficult than expected; the failure of the proposed merger to close for any other reason; the effect of the announcement of the merger on customer relationships and operating results (including, without limitation, difficulties in maintaining relationships with employees or customers); dilution caused by Potlatch’s issuance of additional shares of its common stock in connection with the merger; the possibility that the merger may be more expensive to complete than anticipated, including as a result of unexpected factors or events; the diversion of management time on transaction related issues; the estimation of Deltic’s accumulated earnings and profits is preliminary and may change with further due diligence; general competitive, economic, political and market conditions and fluctuations, including changes in interest rates, credit availability, adverse weather, cost and availability of materials used to manufacture products, natural gas pricing and volumes produced; changes in the regulatory environment; the cyclical nature of the industry in which the parties operate; and the other factors described in Potlatch’s Annual Report on Form 10-K for the fiscal year ended December 31, 2016 and in its most recent Quarterly Reports on Form 10-Q filed with the SEC, or described in Deltic’s Annual Report on Form 10-K for the fiscal year ended December 31, 2016 and its most recent Quarterly Reports on Form 10-Q filed with the SEC. Potlatch and Deltic assume no obligation to update the information in this communication, except as otherwise required by law. Readers are cautioned not to place undue reliance on these forward-looking statements, all of which speak only as of the date hereof.

About Deltic Timber Corporation (NYSE:DEL)

Deltic Timber Corporation is a vertically integrated natural resources company. The Company is engaged in the growing and harvesting of timber and the manufacturing and marketing of lumber and medium density fiberboard (MDF). It operates through four segments: Woodlands, which manages all aspects of its timberlands, including harvesting and sale of timber, timberland sales and acquisitions, oil and gas revenues, timberland management and leasing of hunting land; Manufacturing, which consists of its approximately two sawmills that manufacture a range of softwood lumber products and the Del-Tin Fiber plant that produces MDF; Real Estate, which includes the Company’s approximately four real estate developments and a related country club operation, and Corporate, which consists of executive management and the staff functions. It is also engaged in real estate development in central Arkansas.