There are so many seeds and plants to choose from in catalogues at this time of year, but how do you know you're going to get a great performer which does what it says on the packet?

Consumers' Association magazine Gardening Which? put some new varieties to the test to find out the best bloomers among new flowers.

Researchers tested plants' germination, flowering, foliage and resistance to pests and diseases last summer and reveal the results in the latest issue of the magazine.

The best included the California poppy Fruit crush' (Thompson & Morgan, 01473 695 225, www.thompson-morgan.com), which produced masses of yellow, orange, pink and red flowers from the end of July to the end of August. They don't like the wet, though, so would have probably performed better in a dry summer.

For a stunning autumn show, they recommend the ornamental grass Pennisetum Cream Falls' (Thompson & Morgan, 01473 695 225, www.thompson-morgan.com), planted in swathes through the border and producing long, fluffy, white flowers from July to the end of September.

Long-flowering gems include Viola Pumpkin Pie' (Suttons, 0870 2200 606, www.suttons.co.uk), sown at the beginning of May and producing masses of orange, yellow and black flowers throughout the summer. They are trouble-free and look great at the front of the border or in pots.

If you have a hot, dry spot in the garden where you want to make some impact, go for Nasturtium Paintbox' (Dobies, 0844 701 7625, www.dobies.co.

uk), which produces an impressive red, yellow and orange flowers from July to September. They are good ground cover plants and do well in poor soil.

The enormous flowers of Sunflower Green Heart' (available from Thompson & Morgan, 01473 695 225, www.thompson-morgan.com), which span 40cm, should be enough to dazzle most visitors to your garden.

The plant grows up to 160cm, so is great for the back of the border, flowering from late July to mid-August. You'll attract the birds if you leave the seedheads on at the end of summer.

Of all the plants grown, the favourite was Aster Bridesmaids' (Suttons), which grows to 80cm and produces pink, apricot and yellow flowers, which help soften the look of the border and go well with ornamental grasses.

Seeds were sown in May and germinated quickly, although asters are late-flowering, blooming in August and September.