Its new 16-page factsheet focuses on aquatic plants and looks at controls for pests and diseases, including biological agents.
Communications manager Scott Raffle said: "HDC is often criticised for spending levy payers' money on the most commonly grown horticultural crops.
"But with well over 300 crops to cater for, it is difficult to please all of the growers all of the time.
"Inevitably, growers of shrubs and herbaceous material tend to benefit more because these crops take the lion's share of HDC income from the hardy ornamentals sector.
"But we make every effort to cater for minor and specialist crops and this factsheet is an example of the HDC responding to requests for help from one such specialist sector."
Pest, disease and weed management in ornamental aquatic plants looks at key pests like the two-spotted spider mite and diseases like rust, and offers integrated control measures.
The factsheet's authors, ADAS pathologists Erika Wedgwood and Jude Bennison, followed up on earlier research on nurseries producing fully submerged and pondside plants.
Wedgwood was surprised by the lack of diseases thriving in UK aquatic plant nurseries. Most of the plants were native to the UK and had built up resistance to disease, she concluded.