The Clean Plants program, originally called the Domestic Phytosanitary Certification Program (DPCP), was developed in 2006 by a team of experts operating under Canadian Nursery and Landscape Association (CNLA) supervision.  
This program is currently accredited by the Canadian Nursery Certification Institute (CNCI) and is available nursery growers across Canada.
There are several components and resources available to help nursery growers participate effectively in Clean Plants:

Introduction

How can I apply?

Clean Plants Certification Standards and Appendices

Training Materials, Tools and Links

Clean Plants Certified Nurseries List

Once a nursery has fulfilled all the requirements for certification, the Canadian Nursery Certification Institute (CNCI) will grant that nursery certification in the Clean Plants program. The nursery will then be entitled to use their Clean Plants stamp with their unique Clean Plants certification number. 

Accredited Auditors

Audits by an accredited third party auditor are a key component of the Clean Plants program. Nurseries are free to choose from this list of accredited auditors.

Clean Plants