HTA business development director Tim Briercliffe told delegates at last month's event: "With many garden centres sourcing from up to 40 nurseries, that leaves each supplier with insufficient business to justify close involvement with the retailer."
That contrasts with other categories within the garden centre such as wild bird care products, where suppliers help with ordering, merchandising and promotion, he pointed out.
"Plant producers need to collaborate to be able to work more closely with retailers to work with them to drive sales," he added.
Briercliffe said the industry can carry on "hoping for good weather, positive media coverage and a favourable exchange rate or it can tackle the big issues that threaten the sector in the future".
A "culture change is required to avoid the spiral into commodity, low-margin production that leaves the sector vulnerable to market changes and competition", he added, while the most important challenge is "knowing your enemy".
Knowing your enemy - The top challenges facing growers according to Briercliffe
Competition Cheap imports, other UK nurseries and other leisure pursuits.
Customer demands Better service, quality and value. Products must enhance lifestyle and be easily accessed - online.
Costs Look for savings in transport, sales and input costs - including water, crop protection, plastic, fertiliser, growing media and staff.
Environmental More drought, new pests, diseases and weeds. Increased energy prices and fewer pesticides.
Skills Production horticulture is not attracting young talent.
Regulation On crop protection, water and soil management, plant health and growing media.
Innovation UK nurseries will have to "think smarter" to keep up with declines in research and development.
Supply chain management Product category sales plans need to be agreed between grower and retailer.
Transport and logistics UK growers need to seriously embrace collaborative working on transport.
Market information Pool resources on market intelligence.
Marketing and promotion Producers need to work together to reach the consumer using new technology - internet and mobile phones.
Skills A publicised commitment to training and development will also help, plus e-learning.
Innovation Collective research and development.
Forward-thinking production Fewer pesticides, less fertiliser, less water, sustainable growing media. Develop unique selling points to move from commodity production to premium product.