Plants to look for in May

Hot weather over Easter this year (2019) meant that many plants have come into bloom somewhat earlier than usual. These are some which have featured as previous May Plant of the Month.
Camassia leichtlinii - S Turner Davidia involucrata - K Keeton Lathrea clandestina - K Keeton Paeonia mlokoseitschii - S Turner Piptanthus nepalensis - S Turner
Camassia leichtlinii
In the AGM Borders (Area S) there is lovely display of misty blue Camassia leichtlinii. The six petalled flowers grow round a straight, leafless spire, 70cm tall, rising from the bulbs and basal leaves. Named after a German bulb enthusiast, Max Leichtlin, this is one of 6 species of Camassia, all originating in north west America where they grow in profusion in moist meadows. They naturalise easily and associate well with grasses. The bulbs were a food source for native Americans who used them rather like potatoes and made a flour for bread. In 1805 Lewis and Clark almost died of starvation on their pioneering expedition to the Pacific coast until a native tribe gave them this food.
Davidia involucrata var. vilmoriniana
One of the most spectacular flowering trees is appearing in ‘flower’, and will be looking lovely once we have some warm sunshine. It is the handkerchief tree, Davidia involucrata var. vilmoriniana. We have two trees of this genus in the Gardens. One may be found in the Asia garden (area N), and the other, much younger specimen is in the Marnock garden. It was originally discovered in China by the French missionary Péreé David in 1869, but unfortunately at that time no seed was collected, so it wasn’t until Ernest Wilson sent seed back to Veitch’s nursery in 1903 that this tree became commercially available. What appear to be flowers are, in fact, large white bracts. Wilson considered it to be ‘the most interesting and beautiful of all trees of the north-temperate flora’ and likened the white bracts to ‘huge butterflies hovering among the trees’.
Lathrea clandestina
An exotic, botanic specimen may be found growing on the poplar tree opposite the South Lodge (area V). Lathrea clandestina (purple toothwort), is growing at ground level. It is a parasitic plant growing on the roots of poplars, willows and hazels, and making brilliant patches of large purple flower clusters with hooded upper lips. There are no leaves, and the plants feed entirely on the roots of its host. It was introduced from Western Europe in the 19th century, but can now be seen growing in the wild.
Paeonia mlokosewitschii
In Fours Seasons Garden (Area A), in the second Spring bed on the left after entering from the Botanical Road entrance, a highlight of the garden in May is Paeonia mlokosewitschii From the fat red buds pushing through the soil in late winter the maroon stems slowly unfurl the soft, glaucous-green leaves, followed by gradually swelling flower buds. These open into the loveliest delicate yellow petals with a mass of golden stamens within. The foliage continues to look good through the summer, then in autumn the plant produces a further show when the seed pods burst open to reveal the astonishing fuchsia pink lining with shiny black seeds. This is a plant to enjoy for a good seven months of the year. In its native Caucasus Mountains, it grows in hornbeam, oak and beech forests and although it grows well in full sun it's best in a little shade. The Polish botanist, Ludwik Mlokosiewicz, came upon the plant in 1897 and it was introduced to cultivation in Britain in 1908. In 1929 the RHS bestowed the Award of Merit on it.
Piptanthus nepalensis
This upright, mostly evergreen shrub is one of 2 species in the pea (Leguminosae) family, subfamily Papilionoideae. The leaves of shiny, quite leathery green leaflets make a good foil for the attractive yellow flowers, unmistakably pea-like in loose heads. These are followed by 8cm flat brown pods holdling several seeds. First introduced in 1838 and native in the Himalayas from India to western China, this specimen was grown from wild collected seed and can be seen at the front of the Himalayan Bed (Area N11) at the entrance to the bearpit.
Rhododendron 'Loderi King George' - S Turner Rhododendron 'Old Port' - S Turner Tulipa sprengeri - S Turner viburnum_'Mariesii' - S Turner
Rhododendron 'Loderi King George'
The exquisite scent of R. 'Loderi King George' may first alert you to its presence on the left of the little glade which leads into the Bearpit. The Loderi Group of hardy evergreen rhododendrons were raised by Sir Edmund Loder at Leonardslee Estate, Sussex, at the beginning of the 20th century, when he crossed R. fortunei with R. griffithianum. 'King George' is widely thought to be the best of these hybrids, with huge trusses of lily-like flowers, rose pink in bud and becoming pure white with a touch of green in the throat. The papery reddish-brown bark peels attractively.
Rhododendron 'Old Port'
Springtime in the Gardens always brings an enormous variety of rhododendrons into flower. They enjoy the moist, slightly acidic, fertile soil with a degree of shelter. The genus Rhododendron is one of the largest, numbering over five hundred species, and an enormous number of hybrids. This hybrid, known to be over 100 years old, exudes subtle charm: at 10ft high, its spreading dome is covered in rich plum coloured flowers with wavy lobes in dense clusters. You will find Rhododendron 'Old Port' where the Evolution and Asian gardens meet, not far from Davidia involucrata. Visit throughout the month to see a succession of rhododendrons come into bloom.
Tulipa sprengeri
Later in the month, Tulipa sprengeri, the last tulip to flower, makes an arresting sight where it has colonised the woodland (Area Q10) beneath the grove of Betula albo-sinensis var. septentrionalis. Atop tall, straight stems, the pointed petals are clear red, the outer ones with backs of buff with olive green. Tulipa sprengeri is the only tulip to colonise in this way; the deep bulbs do not tolerate disturbance and propagation is by seed. This species is native to Turkey, but no longer seen in the wild.
Viburnum plicatum f. tomentosum 'Mariesii'
The AGM (Award of Garden Merit) beds display plants which the Royal Horticultural Society consider to be of special worth in gardens. In SBG these beds extend from above South Lodge on the Thompson Road drive to near the fountain, and are crammed with lovely specimens. In the top bed, nearest the fountain, grows a sensational shrub: Viburnum plicatum f. tomentosum
'Mariesii', a Japanese beauty introduced in the 1840s. The wide-spreading branches grow naturally in horizontal tiers with the white lacecap flowers thickly arranged in even rows along each side of the branches, producing a snow like effect. The leaves can colour a vibrant red in autumn.