• AGM plants

    AGM plants have been through a rigorous trial and assessment programme. They are:

    • Excellent for ordinary use in appropriate conditions
    • Available to buy
    • Of good constitution
    • Essentially stable in form & colour
    • Reasonably resistant to pests & diseases


 

Cassiope ‘Muirhead’

This plant is a little star. Related to Pieris, but much smaller, each pure-white bell is held in a brilliantly contrasting red calyx and nods brightly on a neat little evergreen plant. Blooming in April, and sometimes again in the autumn, the greyish green foliage is laid like scales along the shoots. Needs bright light, though not full sun, and humus-rich, well-drained, lime-free soil. Perfect in a trough. H5, height to 15cm (6in).

 

Cypripedium formosanum

Orchids were recently added to the AGM roster for the first time - including garden orchids such as this species from Taiwan. Fresh green, fan-like, pleated leaves set off the delightful white slippers speckled with pink or red freckles. The pouches look a little like deflating balloons. Flowers in late winter and needs frost protection, grow in well-drained, humus rich soil in light shade and feed well. Ideal in a pot. H3, height to 20cm (8in).

 

Dactylorhiza elata

For damper areas of alpine plantings, this is easy, vigorous and colourful - ideal for newcomers to hardy orchids. It has bold spikes of vivid purple flowers, 'each like a neon purple flying seagull with a bulky pelican bill' as it states in the RHS Encyclopedia of Perennials. They are held above dark green leaves from May to July. It spreads steadily into large specimen clumps with impact from afar. Best in light shade, but needs damp soil. H5, height to 45-60cm (2ft6–3ft), sometimes more.
 

Daphne × susannae ‘Cheriton’

This prolific and very strongly scented mounding evergreen is a hybrid between two garden favourites, D. collina and D. arbuscula, created in Hampshire by Robin White. Developing into an impressive plant twice as wide as high, flowers open in April and May and then again from July onwards, each bloom is deep rosy purple and fades a little as it matures. Happy in full sun and well-drained soil. H5, height to 38cm (15in).

 

Dionysia aretioides

Some dionysias take experience and expertise to grow well – or at all. This is the easy one. Making low dense evergreen mounds four times wider than high, the neat little rosettes of tiny green leaves are packed tightly together and topped in March with bright, buttercup yellow, five-petalled flowers. Lovely in a pot in a cold greenhouse, but good outside in a sunny trough or scree protected from winter wet. H5, height to 7.5cm (3in).

 

Hebe recurva ‘Boughton Silver’

Hebes are neat and compact evergreen shrubs that are easy to grow and also boast a bold impact. They are indispensible and this one has real presence. The 2.5cm (1in) blue-green leaves turn down distinctively at their tips and are not only a lovely-all year feature but make a harmonious background for the short spikes of white flowers that keep coming in the tips of the shoots all summer. Appreciates sunshine and good drainage. H5, height to 75cm (2ft6in), eventually.
 

Lithodora diffusa ‘Heavenly Blue’

This easy-to-find garden centre favourite is the perfect impact plant trailing over the wall of a raised bed.

Easy and hardy, it trails effectively or can spread to 60cm (2ft) as sparkling ground cover. The narrow, dark, evergreen foliage is the ideal background for the five-lobed flowers in deep gentian blue which open over a long period from May and through summer. Best in full sun in a lime-free humus-rich soil. H5, height to 15cm (6in).
 

Saxifraga ‘Tumbling Waters’

For the retaining wall of your alpine raised bed, this is unbeatable. Tight clusters of rosettes of narrow silvery leaves are encrusted in white-lime speckles and, in spring, produce reddish stems which cascade downwards carrying a long crowded mass of small white starry spring flowers. The flowers can trail to 60cm (2ft), or even more. Not all rosettes flower each year, individual rosettes die after flowering leaving more for the following years. H5, height to 60cm (2ft).
 

Trillium chloropetalum var. giganteum

Big bold and impressive, originating in just a few California counties this plant has proved easy to grow in Britain. Three bold, diamond-shaped green leaves, spotted in grey and/or maroon, are held at the top of single stems and show off upright, fragrant, three-petalled flowers in reddish or purplish tones or even in white. A shade lover which spreads into dramatic clumps and best in well-drained humus rich soil. H5, height to 45cm (18in) or more.
 

Verbascum ‘Letitia’

We usually think of verbascums as tall and upright, but this prolific plant is the opposite: broad and mounded. A little wider than it is tall, the repeatedly branching stems are clothed in grey green evergreen foliage and all summer are tipped with short branching spikes of bright yellow sterile flowers, each with a purplish ring around the centre. A chance hybrid found at Wisley in 1966, and flowering when most alpines are over. H4, height to 25cm (10in).

 

H1 - H7 indicates the new RHS hardiness ratings.

Full details of RHS hardiness ratings (510kB pdf)

 

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