Director Andy Newman concluded that the sector has a "bright future but many retailers are still delivering the same proposition they were three years ago".
He highlighted competition from multichannels, Waitrose, Crocus, Next, B&Q, Homebase expanding 25 garden centres, The Garden Centre Group buying 10 centres and discounters moving into gardening.
Mdj2 said garden centres should understand more about how their customers are changing by talking to them, watching them and visiting other retailers.
The company added that garden centres need "hero" product categories to define the business. Service needs to stand out and merchandising needs a wow factor, while an online policy and an overall retail implementation plan are needed.
Newman said garden centres need to deliver a more inspiring and exciting store. "Right across retail the bar is being raised. In many garden centres it could be argued that the restaurant now offers a better experience than the store."
He pointed out that they also need to embrace omni-channel to defend existing sales and drive growth. "For example, a regional garden centre chain can trade nationally online or simply offer greater convenience through services such as click and collect or customer reviews," he said.