The Glasshouse borders is the section running from the Glasshouse Landscape to the Fruit Mound and was formerly designed by Piet Oudolf, who took his name off it after disputes. It was planted in 2001. Alex Cairns manages this section.
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| Photo 1: View of the Glasshouse Borders on top of the fruit mound in June. |
The borders are designed into diagonal strips of 'rivers' of grasses and perennials flanked by colourful Salix alba var. vitellina 'Yelverton', S. aurea, Cornus sericea ‘Cardinal’, different Cotinus, at the back of the borders, which are also dotted with Rhus and Glycyrrhiza yunnanensis, which has incredible seedheads throughout winter. As the designer had removed himself from it and it has not necessarily been successfully managed the interests of the borders fluctuate, it comes in and out of interest early summer and probably at its best in autumn, in spring much of it is cut to the ground revealing the gravel bed that it sits upon so is quite barren. The Cotinus is pruned also. It has its moments and is best viewed not head on or from the bottom or the top of the borders but horizontally although it is meant to be best viewed from the fruit mound, as the plants seemed to bleed into each other more and have more impact in terms of combinations. Intermittent smaller gravel paths cut between the borders give the sense of walking through and in between the planting.
The plant palette is pre-dominantly North American Prairie species. The same plants are used more than once with different partners in other rivers. The ethos behind the borders is that plants are left to grow as they are, without staking, feeding or irrigation,. These borders mirror the shape of the traditionally English, cultivated Mixed Borders on the Formal Ornamental team, but are a contrast to the way they are managed.
Over the years many plants have come and gone, gradually moving away from Oudolf’s original plan. This culminated in a name change in 2011, however the philosophy of lower maintenance horticulture, with an emphasis on long seasonal interest grasses and perennials that thrive in the free draining, lower nutrient ground remains. Some of the original key species that have been lost due to not tolerating the conditions or poor performance so therefore removed include: Actea simplex (Atropurpurea Group), Astilbe chinensis ‘Purpurlanze’, Astrantia major, Liatris elegans and Festuca mairie. But if Oudolf was still involved he may well have made changes to the plans himself of choosing plants that better suits that environment, as he had down of his other designs, e.g. the Highline.
Key Plant Species throughout the seasons
Late spring/ early summer
Allium ‘Purple Sensation’, A. ‘Cristophii’ and A. ‘Pinball Wizard’ are the first splash of colour to emerge from the new season’s basal growth. This is followed by among others Tradescantia ‘Concord grape’ and ‘Perinne’s pink’, Centranthus ruber, Salvia ‘Dear Anja’ (from Oudolf's plant breeding days and Phlomis tuberosa ‘Amazone’. Slightly later are the purple Veronicastrum ‘Adoration’, V. ‘Fascination’, and the lilac coloured ‘Lavendelatum’ as well as Phlox paniculata ‘Blue evening’.
Mid-summer
The Borders are in full flow with Echinacheas playing a starring role, mixed in with grasses such as Molinia ‘Karl Foester’ and Calamagrostis x acutilflora ‘Karl Foerster’. Drifting throughout all the rivers is the highly and slightly too successful Eryngium gigantium ‘Silver ghost’. Cool colours come from Echinops ritro ‘Veitch’s blue’ and Perovskia atriplicifolia ‘Little Spire’, whilst in the shrub layer the rarely grown Glycyrrhiza yunnanensis complements the pink flowers of Sambucas nigra
‘Gerda’.
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| Photo: Calamagrostis x acutilflora ‘Karl Foerster’ |
Gaura lindheimeri 'Whirling Butterflies' and Eupatorium ‘Purple bush’ are two of the late summer flowerers along with Helenium ‘Riverton Beauty’ (Alex talked about Hampton Court chopping these
so that they didn't get so leggy).
Mid-autumn
The grasses are now the key attraction along with the herbaceous seed heads. The borders have evolved in to colours of gold and yellows which look stunning in the sunlight. Many species of bird enjoy the chance to feed on the seed heads which will stay stand well in to winter, and the back of the borders show their fantastic autumn colours of reds, browns and yellows.
Winter
On frosty days the seedheads and grasses can provide an amazing winter scene. Most of the plants stay standing until the big cut back around February to give maximum interest through the year before the new growth starts.
Management of borders
Originally the beds were bare soil but to help reduce weed growth, a decision was made to put down a thick layer of gravel mulch. This has been topped up over the years and was last done in February 2011 where 60 tonnes of gravel was used at a cost of £3500. There are also other issues, though the borders don't get much pests and diseases, plants like the Phlomis tuberosa 'Amazone' gets alot of powdery mildew.
Growing season
Weeding is a mammoth task due to the size of the borders so more attention is paid to the front of the borders removing weeds and keeping the front edge looking smart. The Eryngium ‘Silver ghost’ needs to be controlled at this point to prevent it taking over. Hoeing large areas is an effective method as the large tap roots are too difficult to dig out and herbicide spraying has proven ineffective when tried. There is unfortunately a huge equisetum problem there, these are at present weeded out by hand and thrown away (not in the compost).
In early summer anytime from May to July the Helenium ‘Riverton beauty and Sedum ‘Matrona’ benefits from cutting back by up to half. This technique often referred to as ‘Chelsea chopping’ can be applied to many species to prevent plants from becoming too leggy, encouraging a more compact plant with delayed flowering to prolong the season. This creates a more interesting view with varied heights of cut on the same plants, so your eye follows to the back of the border, rather than facing a block of tall plants.
*Further reading on cutting back and pruning: The Well-tended Perennial Garden: Planting and Pruning Techniques by Tracy Di Sabato-Aust
Late winter
The herbaceous plants are cut back using brush cutters then the debris is raked in to piles and loaded on to trailers for composting. The process can take two days with a group of up to around ten people.
The varieties of Cotinus and Rhus respond well to late winter hard pruning, producing larger leaves although this will sacrifice the flowers. Each year it is decided which plants would benefit from hard pruning and those that would look good being left to flower. They have found it better to work on a program of several years in order that plants are not over-pruned, so there will always be some flowers particularly from the Cotinus. Cultivars that look particularly good for inflorescence are C. ‘Flame’ and ‘Pink Champagne’. C. ‘Royal purple’ and ‘Grace' look fantastic when hard pruned with bigger dark purple leaves.