Cambridge Botanic Garden Report 29-10

Cambridge Botanic Gardens 29th October 2011

Group picture (courtesy of Raoul) on the roof terrace of the Sainsbury Laboratory

A group of 20 Kew guild members were delighted to be welcomed by Tim Upson, Curator, of the Cambridge Botanic Gardens at the Trumpington Road garden gate last Saturday with temperatures well above normal for the time of year and the sun breaking through. It was an ideal time of year to be visiting to see some autumn colour, for late flowering salvias and grasses as well as to hear of the new developments at the garden.

Liquidambar styraciflua 'Worplesdon'

Notes on the Gardens

Cambridge Botanic Garden comprises 40 acres as part of the teaching facility of the University of Cambridge, Department of Botany. Founded in 1846, it follows the abandonment of a physic garden which existed in the centre of the city from 1762, contemporaneous with the Chelsea Physic Garden and Oxford Botanic Gardens.

Key to its development was Professor John Stephen Henslow, Professor of Botany (1825-61) whose interest in trees led to more space being required than that afforded by a physic garden. His collection of trees amongst which the pines are notable (and much appreciated on the day), were selected for the variation they showed within species and make a fine feature. He was already beginning the move to consider what Darwin was to demonstrate much later that species were not immutable, and it is significant that he had mentored Darwin and wrote the letter of recommendation which enabled Charles Darwin to join HMS Beagle in 1831.

The gardens were designed and developed to display strong taxonomic links and, formed as they are as a plan of 4 quarters, today succinctly accommodate lake, rockgarden, two sets of glasshouses, the systematic beds and the arboretum. The systematic beds follow the traditional system established by the Swiss botanist De Candolle rather than the APG system (Angiosperm Phylogeny Group) in current use.

Order beds according to De Candolle

The gardens are worked and managed by a total of 20, including 6 teams of 3 to look after different areas of the garden, plus 6 paid trainee gardeners who receive an accredited award following the 1 year course. Funding for the garden is 1/3^rd from the University (probably going down), 1/3^rd from the Reginald Cory fund (stable) and 1/3^rd from public admissions and visitors whose numbers have now reached 200,000 a year (potentially going up!).

From 1950 more land became available from allotments and due the endowment of Reginald Cory, there was an opportunity to increase the area of the garden in which to develop the woody plant collection and replant many of species in the original garden. Bounded by the town’s residential building programme of flats and houses today, this area provides a suitable complement to them but with almost none being visible from the gardens itself due to the planting. One building which is visible is the brand new iconic Sainsbury Plant Sciences Laboratory (architects Stanton Williams) endowed by David Sainsbury and opened in April this year which we were privileged to visit. A strong but restrained design in warm Caen stone and glass, with a courtyard of olives, and a well-planted and diverse landscape by Brita von Schoenaich, it completes a composition which includes a restaurant for the public and the old directors house, Cory Lodge now absorbed as part of the gardens.

Plant Notes

At the Trumpington Road Gate, the first immediate view is of a large group of Pterocarya fraxinifolia. Once two single trees planted either side of the existing small lake feeder stream, they are now a multi-stemmed mass of trunks which have formed as suckers from the original trees. The high water table has favoured their success, although their current size is a difficulty to maintain. Opposite this group a large specimen in the same family, Juglans nigra was displaying a clear autumn yellow characteristic of the tree. Trees form the backbone of the garden and the warmer climatic conditions experienced seem to be helping many trees. Quercus velutina and Q shumardii are two from the warmer parts of Eastern N America which have done well and are showing autumn colour. Showing no colour at all but eagerly producing fruit (for demonstration purposes?) was a seedling tree from Newton’s original apple tree growing nearby.

The garden generally emphasizes less separation than previously between amenity, botanical resources and education and over the course of time the traditional bedding plants in front of the glasshouse range have been replaced by herbaceous perennials and supplemented with bee hives.

Salvias (in particular Salvia elegans, both the tangerine and pineapple forms; S leucantha and S involucrata Bethellii), are very much in evidence in the area between the greenhouse wings behind the hives where a sheltered microclimate exists.

Salvia elegans

Salvia leucantha

Instruction being taken

Salvia enclave with S. elegans and S. leucantha in the foreground

A distant look at the oleaceae collection identified copious amounts of mistletoe on the limes. 30 years ago, this was the most northerly occurrence of mistletoe (now it is found as far as Nottinghamshire) but its abundance here is a mystery. Spread by birds, most noted in the Cambridge gardens by mistle thrushes and blackcaps, the explosion of mistletoe has also been found at EA Bowles garden (Myddelton House, Enfield). Although only about 10 species of trees are colonised by mistletoe, its spread is thought to be caused by the protection of a limited number of bird species which are known distribute it, and the proximity, safety and reliability of suitable habitats for them.

Mistletoe in lime amongst the Oleaceae collection

Parrotia persica in fruit

Parrotia persica had, unusually, not coloured this year, but had redeemed itself by producing seed and was also notable in the Cambridge specimen for the cross-grafting between branches. Seedlings and invasive species go together and Tim had noted more Broussonetia papyrifera progeny than usual. Hamamelis virginiana is one of the first to flower despite not losing its leaves in our climate. This is a disadvantage since the flowers become invisible. Quercus warburgii, the Cambridge oak is a garden hybrid between the Mexican oak and common oak (Q. rugosa x Q. robur). As a huge tree it may have been favoured by the warmer climate we have experienced, but it is famous for the bright red foliage it produces in early spring. Now infected with ganoderma, its decline is being managed and it is treated as a veteran tree with the dead wood left in place.

Varieties of Pinus nigra which date from Henslow's day.

A magnificent wide-spreading brown-orange Zelkova (Zelkova serrata) planted in 1960 contrasted with its green relative Z carpinifolia and showed it to be the more attractive tree. Enjoying wide-spreading trees such as the Zelkova and Pterocarya is becoming an increasingly rare experience, especially in towns.

Zelkova serrata

Malus trilobata (it could almost be a Crataegus?)

Pistacia chinensis

Autumn colour was most notably represented by Liquidambar styraciflua ‘Worplesdon’ (see above: first photograph) (with Liquidambar orientalis still green and yet to show). Malus trilobata was an unusual inclusion being of almost Middle Eastern origin, and in particular Pistacia chinensis, from central China a vivid yellow-orange) One further tree, in fruit rather than colour, was Platycarya (Platycarya strobilacea) an Asian relative of Juglans which uniquely showed its winged (and airbourne) fruits suggesting a lineage predating animals which characterize its relatives in Juglandaceae. Platycarya fruits have been found laid down in the London clays. Malus transitoria (a NW Chinese species: See under M. toringoides in Bean ) made a significant impact in clear yellow adjacent Cory Lodge.

Platycarya strobilacea (wing-seeded Juglandaceae)

Besides the usual colour subjects of Cotinus and Euonymus which featured towards the Station Road gate, Prunus verecunda 'Autumn Glory’ was significant. This is now a new area in which to demonstrate the species of new plant research and showcase them.

Aesculus califonica against a backdrop of 'leylandii', (the correct use of the conifer?)

View of the Sainsbury laboratory from the arboretum. (Malus transitoria (yellow) to the right in dintance)

The walk trough the gardens concluded with a visit to the Sainsbury Laboratory in which we were treated to an inside view of the main building. Fantastic laboratories with rest and discussion areas (complete with white boards!) surrounded two side of a courtyard of olives (Olea europea). A further plant growing centre and amenity facility for the garden made up the complex. An integral public restaurant has also been included, with a patio enhanced by Tilia henryana flat-trained as ‘roofs’ to provide future shade. (This species, along with T. x euchora and T. petiolaris, have the advantage of discouraging aphids by their hairy leaves). Flat ‘tables’ of yew laid out in a formal manner divide areas of herbaceous perennials and grasses which will give all year interest. The frontage of the building is formed as a grove of Ginkgo biloba surrounded by cut yorkstone paving. Whether these are male or female has yet to be seen.