Most topsoil bought by gardeners is also of poor quality, says Gardening Which?, published yesterday. All the samples it tested were deficient in nitrogen, nearly a third were infested with weeds and some samples contained more than 25 per cent rubble.
The association examined eight plant types at 60 garden centres and found that only 12 merited top marks from experts for four or more plant types. Plants in poor condition were found at even the best garden centres.
The survey also found there was no significant difference between members of the Garden Centre Association, which aims to 'lead the way in instilling a culture of quality in garden centres', and other centres. Chains were no better than independent nurseries, although the three branches of Hilliers examined were 'reasonably good'.
Problems result from poor stock from the grower, lack of care by the centre and plants being left on sale for too long. Buyers are advised to look out for weeds in pots, faded labels and pot-bound plants. Plants should be well spaced, not sitting in puddles of water.
The magazine also says that neither price nor supplier could guarantee topsoil quality. The best soils ranged from pounds 18.80 to pounds 164.50 a ton. Alistair Ayres, editor of Gardening Which?, said: 'Some of the soils we tested were so full of debris that sieving through them was like taking part in an archaeological dig.'