Top 20 bulbs and perennials for your garden

Bombproof plants always come up smiling whatever the weather or the conditions. They never, however, veer towards thuggery.

They are the Joanna Lumleys of the gardening world - good looking and refined. Finding them can take years, but you can short-circuit the process by looking for the Award of Garden Merit (AGM). It's depicted in the RHS Plant Finder by a trophy logo.

1 Sedum telephium 'Purple Emperor' AGM

The best dark-leaved sedum. The fleshy, sultry foliage is neatly crimped, the red-pink flowers appear in August (far earlier than S. spectabile cultivars) and the plant never gets untidy. Close runners-up include 'Xenox' and almost-identical 'Karfunkelstein'. Chelsea-chop them (ie cut back in mid May), for much later flowers and always give them sun (2-3ft).

2 Aster x frikartii 'Mönch' AGM

This long-flowering aster begins in July and produces large, long-rayed daisies in soft lavender-blue until September. It's a hybrid between two drought-tolerant European species (A. thomsonii and A. amellus), so won't succumb to mildew like many North American asters. The habit is slightly floppy, the foliage is dark and robust, and it's perfect at the front of a partly sunny border (3ft).

3 Dahlia 'Bishop of Llandaff' AGM

Bred by Welshman Fred Tredegar in 1922 and selected by the Bishop, this vintage, peony-flowered, strawberry red dahlia has dark, divided foliage. Other stalwart dahlias include 'David Howard' and 'Magenta Star', but the Bishop will out-perform almost any other, even in dull, cool summers (3ft).

4 Crocosmia 'Lucifer' AGM

Alan Bloom's bright red crocosmia, bred in 1966, has sword-shaped, pleated leaves in just the right shade of green to flatter the fiery, upward-facing flowers. These appear in July in profusion and 'Lucifer' blazes away in the midsummer border (4ft).

5 Helenium 'Sahin's Early Flowerer' AGM

This helenium begins in early July and carries on until late autumn as long as you shear off the first flowers. Every flower is uniquely streaked in a mix of orange, yellow and red and this vigorous hybrid is much easier to grow than thirsty Helenium autumnale cultivars (3-4ft).

6 Helianthus 'Lemon Queen' AGM

A tall, lemon-yellow daisy that stays in a tight clump, unlike most of the tribe, and never needs staking. It flowers from August on and was bred at Thomas Carlile's famous Loddon Nursery in Twyford, near Reading (5ft).

7 Geranium 'Orion' AGM

The best deep blue hardy geranium, with large flowers, divided green foliage and a mounding habit. It flowers from May on and keeps going. Allow it to flower early and then cut it back for a long second flush. The magenta pink 'Patricia' ('Brempat') AGM and the soft blue 'Rozanne' ('Gerwat') are also sterile AGM winners (2ft).

8 Rudbeckia fulgida var. sullivantii 'Goldsturm' AGM

The crispest, brown-centred yellow daisy on offer and always in flower by August. Bred in 1937, it outshines the other black-eyed susans by a mile. Prefers moist soil and, like all daisies, it must have good light (3ft).

9 Stachys officinalis 'Hummelo'

This refined plant is a Piet Oudolf introduction and performs best in fertile soil in full sun despite its common name of wood betony. The stiff, square stems are topped by dense orchid-like spikes of purple-pink flowers and there are lots of them tightly packed together. So this relatively short plant makes an impact and gives vertical accents among summer-flowering herbaceous plants (up to 2ft).

10 Echinacea purpurea

The purple cone flower, a stout-stemmed daisy that makes August bearable, should find a place in every garden. In the wild they endure warm summers and cold winters, and therefore resent warm, wet winters. Find the largest plants you can and plant in spring or summer. 'Fatal Attraction' has wonderful buds and the statuesque 'Rubinstern' AGM is a strong pink, but all need good soil (3ft).

11 Origanum laevigatum 'Herrenhausen' AGM

The sugar-rich nectar makes this plant an ideal magnet for butterflies and bees in early August. 'Herrenhausen' is the finest form, with pale pink flowers held in pristine purple calices. The two-tone effect of this branching flower head is made lovelier by the dark, wiry stems and dark mat of aromatic foliage. Holds its flowers for weeks (2ft).

12 Sanguisorba officinalis 'Arnhem'

The fashion for taller grasses has fostered a need for taller perennials and the raspberry-red bobbles of this July-flowering sanguisorba have an airy presence. The foliage stays neat and the willowy, branching stems move and sway, rather than going straight up. The flowers fade to brown and seed heads persist into autumn (5-6ft).

13 Anthemis 'Susanna Mitchell' ('Blomit')

Pallid lemon flowers make a wonderful foil for purple, blue and magenta, and Anthemis 'Susanna Mitchell' will provide hundreds of delicate daisies from May until late autumn. The sprawling habit and early flowers come from the white-flowered A. punctata subsp. cupaniana. The filigree silver foliage is a bonus, but deadhead and cut hard back after the first flush. Propagate regularly (1-2ft).

14 Aquilegia chrysantha 'Yellow Queen'

Forget granny's bonnets, this graceful two-tone primrose yellow and cream American aquilegia has tapering swept-back spurs and a flouncing skirt. In a shady border the flowers seem to float across the garden. This tall, fragrant aquilegia flowers for much longer than most (4-5ft).

15 Gladiolus murielae

Pure white, six-petalled flowers attractively stained at the centre with burgundy-purple, make this the most tasteful gladioli. Plant several in a pot in spring and bed them out in mid summer to fill the gaps (4ft).

16 Achillea 'Moonshine' AGM

Find a warm, sunny position for this acid-yellow achillea, raised by the late Alan Bloom of Bressingham, and it will flower from May until October. Very hardy, but replace every fourth year to prevent woodiness (18in).

17 Heucherella 'Kimono' AGM

Choose a quieter, sheltered area of the garden to enjoy the silvered, jade-green foliage zoned and veined in purplish black. Dainty sprays of flowers follow, although this plant is grown for its kimono-shaped lobed leaves in late spring. Dappled shade is perfect and summer moisture appreciated (21in).

18 Anemone x hybrida 'Honorine Jobert' AGM

This single white Japanese anemone has the purest flowers. It is graceful from afar and perfection up close with its green eye surrounded by a wreath of gold stamens. The dark green foliage makes the flowers even more virginal. Let it roam close to walls and buildings (4ft).

19 Kniphofia 'Wrexham Buttercup'

This cool yellow poker majors in August and September and it shone at the RHS trial of kniphofias. It produces lots of softly tactile flowers; they begin green, turn a warm yellow and then age with a hint of ripe peach (3ft).

20 Aconitum carmichaelii 'Arendsii' AGM