The HTA Ornamentals Committee and Retail Management Group have endorsed the guide, which outlines standard terms and conditions that members should be including within their own terms.
The terms mirror the Government's Prompt Payment Code and should be checked by a solicitor.
HTA president Andrew Richardson said: "It is paramount that cash continues to flow from business to business within the horticultural supply chain and, by working with both growers and retailers, the HTA has produced a number of industry recommendations, which underpin good trading practice.
"While not meant to be prescriptive, the guide will help members to ensure that they are including all the essentials within their own terms and conditions."
Retail Management Group chairman Caroline Owen said: "A robust set of terms and conditions provides a platform for discussion between suppliers and their customers to ensure that everyone works together to maintain an efficient trading cash flow within businesses in the garden retail supply chain."
Payment is due 30 days from the date of invoice.
Any damage, shortage, pilferage or rejections/returns on quality grounds must be informed to the supplier within 24 hours of delivery of the goods.
See the HTA's information sheet 50, available at the organisation's website.