As observed during April 2008
1/4/2008
Pillars and palms, the very best of Victoriana
Come in, look up, and appreciate the leafy canopy of the palms and the Victorian ironwork of the Temperate Palm House. April the first is the day 150 years ago that the Temperate Palm House opened its doors to the public allowing access to many newly collected plants.
It is, at 21.95 metres (72ft), the tallest traditional glasshouse in Britain. Reading the description of the building in the July 1858 edition of the Transactions of the Edinburgh Botanical Society, Professor Balfour wrote "that he believed it was the tallest palm house in the kingdom".
A vote in 1855 of £6000 from Parliament enabled work to commence in May 1856. On completion, the total cost was £6500. The iron work for the double roof dome and the 14 supporting cast iron pillars were cast at the Shotts Foundry. The mellow sandstone blocks originate from a quarry at Bishopbriggs where the pale grey to white coloured sandstone of the Carboniferous age was laid down in a sedimentary basin.
The house was constructed slightly earlier than the Kibble Palace, another iconic botanic structure in Scotland, which has also recently undergone refurbishment of its glass frame and planting within Glasgow Botanic Garden.
Walk in from the cold and there is often a scented air to the interior. During March this was the white-flowered Jasminum polyanthum, a scandent plant from China that revels in the support allowing it to climb with ease from ground level to the height of the first balcony. A few flowers remain allowing the occasional drift of scent to be appreciated.
We do need to concentrate on the palms, the group of plants the house and its earlier (1834) tropical neighbour were named after. The tallest plant in the house is Howea forsteriana, commonly known as the Kentia palm, from Lord Howe Island. It is laden with fruit, green to red to black in colour - the raw material which provides work for islanders on Lord Howe Island, a Pacific paradise to the east of mainland Australia.
Once the whaling industry declined, the collection and export of seeds from this and H. belmoreana developed. Seed collection in the wild is a regulated process as both endemic species are categorised as vulnerable on the IUCN red data list. A specialist nursery on the island germinates and grows on for export worldwide seedlings to fulfil the constant demand for specimen plants in the interior landscape industry. It is the most popular palm sold in the garden centre trade. Kentias are ideally suited to office buildings, shopping centres and indeed as a pot plant in the home due to its tolerance of relatively low light levels.
7/4/2008
Ercilla volubilis collected in Chile during 1996 by the ICE team, a collaboration between the Royal Botanic Garden and the Instituto de Investigaciones Ecologicas Chiloe. It was observed in the wild growing to 3m in height with clusters of fleshy orange-red fruits. Located at the giddy altitudinal height of 14m, inland from the coast by 1km, forming the original coastal forest margin.
At Edinburgh, it is growing very successfully with the protection of a south facing wall behind it in the Chilean area to the north of the Glasshouses, with the support of which it has reached 2m+. Fresh growth in a favourable south west lee of the wall has already shot to 200mm this year.
Brown adhesive pads emanate from behind the leaf axils to hold the stems to the brickwork. It is essential these grip into the bricks surface when the vigorous growth is young as the combined weight of stem, leaves and flowers will cause growth to collapse away from the wall. Where this happens it is best to cut these out and allow fresh shoots to fill the space.
The evergreen leaves are ovate rounded with a firm feel to them. From the leaf axils the flowers drop out on stalks 75mm in length, not attractive, but noticeable. The ball-shaped buds open and the whole drooping spike then resembles a faded pink candyfloss-like tail up to 60mm long. Having a slight musty fragrance, more noticeable as the temperature rises. These also attract early bees on the lookout for a nectar source.
11/4/2008
Two twiggy shrubs
The deciduous woody shrub Parrotiopsis jacquemontiana is a member of the Hamamelidaceae family and hails from the Himalayas. Plants are found growing in the north-west frontier province of Pakistan on west facing slopes with scree at 2700 to 2980 metres.
The terminal brown felted buds open slowly to reveal the conglomerate mass of flowers, of which the yellow anthers are prominent. Further opening of the bracts reveals the inner white colour. The combined flowering gives a light appearance to the mass of twigs. At this time the new leaves are forcing through at the corners of the flowers. Planted near the road edge within the Hamamelis collection, the twiggy mass is flowering well this year. The individual flowers are relatively attractive but don't expect the seductive scent that the Hamamelis plants provided. It's not a thing of beauty when in flower but will attract the botanically interested.
For a delightful scent and showy blooms, walk over to the Demonstration Garden, here Viburnum carlesii 'Aurora' is changing from tight red bud to open white blooms. The scent thrown out from the rounded cymes by a mature plant on a warm day is exceptional.
The species is native to Korea and Japan's Tsushima Island, in the Korean Strait from where seed was sent to Slieve Donard Nursery in Northern Ireland. Here Leslie Slinger selected out seedlings and introduced 'Aurora' to the trade in 1958. It received a well deserved Award of Garden Merit from the RHS in 1984.
Our plant is a very good form, displaying a mass of flowers. In bud, they are carmine red and on opening they're white tinged pink. Within some of the individual flowers the anthers are prominent, on others subtended. The stigma lies at the base of the tube red in colour.
Leaf growth and development is well advanced, highlighting the flower colour. The plant has a rounded shape with vigorous water shoots arising from its centre.
14/4/08
Spines from the southern hemisphere
If there was ever a plant to deter all comers this is it. The leaves of Berberis darwinii are clothed in lethal spines. Anyone who has cultivated around or weeded beneath the canopy of this plant will have experienced the spines hanging from the flesh of their hands and gathered on clothing during the process. This however did not deter Charles Darwin, who, as naturalist on the voyage of the Beagle discovered the plant in 1835. It was subsequently introduced to Britain by William Lobb in 1849 from Chiloe.
The tri-pointed, dark, glossy evergreen leaves sport a spine at each point of the apex. Other spines are found on the leaf edge. What makes this plant so useful is the prolific flowering and strong evergreen mass that it grows into. It is ideal as a boundary screen or due to the vigorous growth, as a shelter belt plant. Prune flowered growth immediately after flowering before the black fruit has a chance to ripen and shed its fertile seed.
Our plant to the west of the Glasshouses Front Range towers to five metres and has a stabilising root system rarely damaged by wind. A row of these plants will also make a thick, impenetrable hedge.As the golden yellow flowers held on drooping racemes disintegrate the ground beneath becomes a yellow sea of spent flower parts.
18/4/08 
Clematis armandii
This evergreen climber is found growing at altitudes from 100 - 2400 metres in forests and along forest margins in its native China. Gripping, for want of a better term, hold of anything to haul itself up through the branch framework of supporting vegetation for exposure to sunlight.
The leaf is made up of three glabrous, leathery, narrowly ovate leaflets. It is the petiole of these individual leaflets that on touching a potential support kinks itself around and grips tightly. This supports the advancing growth which in the corner of the quadrangle at the Front Range has gained five metres in height through a Viburnum tinus. The new vegetative shoots are a deep bronze red.
Needing a sheltered spot to avoid winter die back and to promote flower bud formation; this specimen has thrown out a couple of flower trusses that open pure white from globose silvery buds. The individual flowers comprise 6 petals with a central boss of stamens, topped by light coffee brown anthers.
22/4/08
A worthy champion
On the Pyrus lawn to the south west corner of the garden is Pyrus korshinskyi. Registered in the Tree Register of the British Isles as a champion tree, it was last measured in 2004 at 8 metres height with a trunk girth of 1.26 metres. This is one of several specimens to be given champion status in the collection at Inverleith.
The ornamental pears are truly magnificent in blossom and this specimen excels in expectation. A deciduous tree that is sending out fresh leaf but this is overwhelmed by the profusion of blossom terminating the shoots.
The leaf petiole is tinged red matching in with the tight bud colour. As development continues the 5 petals become pure white which contrast with the vermillion red anthers. In the centre of the flower is the split stigma, three pin like points triangulating away from each other.
The bark is deeply and attractively fissured from the trunk into the mature and extensive branch framework.
Go now to appreciate this venerable addition to the garden.
25/4/08
An early flowering perennial
Underestimated and undervalued, Doronicum ‘Miss Mason', this early flowering, early leafing perennial is worth a place in all gardens. Reliable is its middle name, not a year will pass without a generous supply of single yellow composite flowers sent to a maximum height of 400mm.
Easily propagated by division, this is best done in late autumn allowing the rejuvenated roots to establish, resulting in flowering the following spring. Due to its growth pattern and its dislike of a dry root zone during the summer it is prone to grow outwards from the centre of the clump. This leaves the middle with weak growth, necessitating regular division to maintain the vigour of the clump.
Due to the brightness of colour it looks out of place when planted in a sea of green. Doronicum is best appreciated as a larger group, placed with other seasonal flowers, e.g. the later flowering daffodils, the perennial honesty, Lunaria rediviva. Tolerant of shade and here watch the flower heads twist to face the sun. In bud the flower is protected by the green sepals which have a parcel twist at the top. On opening these green sepals spread beneath the ray florets enhancing the petal colour.
A semi double flowered cultivar also worth growing is D. orientale ‘Spring Beauty', seen growing in the herbaceous border. Slightly less vigorous, to 300mm, producing large heads, 65mm in diameter with masses of yellow ray florets. Both cultivars have green stems with a white pithy inner, holding heart shaped, mid green leaves with a serrated edge.
29/4/2008
Floral structure to delight students of botany
Akebia trifoliata a deciduous woody climber native to China and Japan. Found growing in full sun in moist heavy loam in a valley bottom of the Kamagone River at 655 metres. Climbing to 2 metres through Sasa sp., Euonymus sp., Viburnum opulus and Ulmus davidiana.
The flowers are of botanical interest rather than aesthetic beauty. The racemes hang down from the leaf axils, composed of separate male and female flowers on the same raceme.
The wine red female flowers are largest and individually made up of 3 sepals containing the stigma and styles, hanging beneath these are the smaller male flowers. The smaller sepals reflex back to show the black anthers which open to release white pollen.
At this stage the trifoliate leaves are developing with an indented notch at the tip. There are three interesting lobes on the leaf edges. Growing on the west facing wall on the East side of the garden, twining anticlockwise to a height of six metres.
For previous years' highlights during this month, see the April Garden Highlights Archive page.