Gardening Which? magazine tested six gardens over a period of three years and concluded that those left alone did just as well as those fed with artificial fertilisers or organic manure.
The report concluded: "Sadly for the fertiliser industry, our trials have shown that, in the majority of cases, it's not worth bothering to feed your gardens at all."
Each garden tested included a lawn, bulbs, perennial plants, climbers, shrubs, strawberries, vegetables, a rose and a dwarf tree.
Only four of the gardens were fed, two with liquid and Growmore fertilisers and the other two with manure and liquid comfrey plant.
After three years the Which? gardeners found no significant differences between the gardens.
A spokeswoman said: "Plants in the fed gardens did grow slightly lusher and lawns needed cutting more often but there were no real advantages in adding extra nutrients to the soil."
Additional trials involving more than 25,000 plants and 22 different fertilisers yielded the same results.
Alistair Ayres, the editor of Gardening Which?, said: "Feeding is only worthwhile for a few greedy crops like cabbages and for plants in containers but in the majority of cases it is not worth bothering to feed gardens at all."
But John Cushnie, a frequent panelist on the BBC's Gardeners' Question Time, said: "I do agree that fertiliser is possibly overrated and that too much of it is used.
"But the report said that plants in the fed gardens were lusher and a lovely velvety green lawn is what most gardeners strive for."