Garden goods have rocketed in value after the rainy peak season prompted retailers to slash their prices to shift stock.
A representative of Garden Centre Group, which is selling plants in its 129 stores at a discount of up to 50 per cent, said: "Summer has been spectacularly awful so far and, as a result, our summer sale is even better (for consumers) than usual."
B&Q has reportedly also "slashed margins", with sales of items such as hosepipes down by 42 per cent this spring. The retailer is selling twin-pack disposable barbecues for £1.
Elsewhere, Wilkinson has halved the price of a reusable barbecue from £6.98 to £3.49 and Sainsbury's is selling disposable barbecues at 20p, reduced from £1.70.
Tesco and Asda are both selling four disposable barbecues for £2 and at Wilko, garden furniture and barbecue prices have been cut by up to half.
Poor sales were reflected in B&Q's first-quarter profits, which were down £29m on the same period in 2011. Meanwhile, Homebase reported an eight per cent decline. Sales of mowers, heaters and gazebos were up, but those of garden furniture, barbecues and hosepipes were down.
Ian Cheshire, chief executive of B&Q parent Kingfisher, said: "The unprecedented wet weather has continued into our second quarter - we took the necessary promotional action to clear horticultural stocks."
But some garden centres have decided not to discount their stock until after the Olympic Games.
Clifton Nurseries managing director Matthew Wilson said: "People's attention will be on the games and they will not be coming to buy plants. So we'll be starting our sale a bit later."
GfK figures for June show the homewares market, including outdoor furniture, declined by 26 per cent in volume.
Furniture sales declined the most, dropping by 35 per cent. However, in the month's warm week, outdoor furniture was worth £27.3m and accounted for 31 per cent of total furniture market sales.