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Cambridge University Botanics Mountain Plants Diary

This entry: September 2012 Mountain Display House by Simon Wallis and Helen Seal

After a couple of months outside in the Garden it’s time to move under glass and have a peak at our Mountains house. The Mountains house is part of the larger Glasshouse Range, originally built in the 1920s, that is themed to explore the drama of plant diversity and visits a variety of different habitats, including life in a cold climate in the Mountains house. A major renovation started back in the summer of 2006 when all the old landscaping and plunge beds were removed and replaced with new hard landscaping and display beds. This month’s dairy focuses on the main, larger section of the house.

This section has a large central raised bed landscaped with tufa and contains a wide variety of horticultural alpine plants including Towsendia incana, Primula allionii, Campanula fragilis and various Saxifraga and Sempervivens species.


The tufa bed

Campanula fragilis tumbling over the tufa bed



One of the plants looking good and this time of year is Polygala chamaebuxus ‘Rhodoptera’. A rather gaudy milkwort with its yellow keel and pinkish-purple laterals, this is mat forming perennial, flowering for many months of the year. We let it ramble amongst other plants close by. Some plants such as Saxifraga maderensis and Erodium reichardii are growing directly in the tufa. In these cases they are grown in naturally occurring holes or a small pre-drilled hole and then the alpine is planted directly into the tufa with the additional of a gritty compost mix.






Saxifraga maderensis growing in tufa with Verbascu

The tufa in the bed is well watered using rain water, twice a week in the summer months, but less often in the winter months. The tufa acts as a natural sponge, retaining some water, but allowing excess to drain away. Amongst the alpines, some self-sown ferns such as Asplenium scolopendrium are happily growing away, indicating that the bed is getting enough water from just soaking the tufa around the plants. The growing media used in this bed is an experimental mix of 25% composted bark, 25% sterilised soil, 25% grit, 15% sand and 10% Toresa wood fibre with some additional minerals. Judging by the healthy and stocky plant growth, it seems to provide a good balance of drainage and nutrient.     

Asplenium scolopendrium self seeding in the Pimele

An unidentified fern growing in our tufa bed

Down the east and west sides of this section of the house are long plunge beds. These displays change continually through the year, as sub-alpine and alpine plants usually held in the reserve collection are brought in at their peak interest. Again these beds are watered twice a week and the plants checked over.  Any plants past their best are then exchanged to ensure the displays continue to look attractive all year (a real challenge in mid to late summer).  


One area of the eastern bed is used to display shade-loving plants, and can include Saxifraga stolonifera, Soldanella villosa, and Roscoea alpina. At this time of year, flower is minimal but we see this as a great opportunity to highlight the great variety of foliage colour and shapes, and different growth forms. All the pots are plunged in a mix of coir and sand topped off with a layer of sieved leafmould.  


The shade lovers' plunge bed

The northern end of the east plunge bed displays a wide variety of our geophytes. This is always a popular display with many showstoppers making an appearance during the year


The geophytes plunge bed

The real star this month is the flamboyant summer dormant, Nerine sarniensis. This spectacular crimson flowered member of the Amaryllidaceae family originates from South Africa and has naturalised some cliffs in Guernsey, hence its common name the Guernsey lily. The flower buds emerge in early autumn with each inflorescence carrying up to fifteen flowers, followed shortly afterwards by the leaves.

Nerine sarniensis

Other geophytes looking good at this time of year include many of the frost intolerant cyclamen such as Cyclamen africanum, C. mirabile and C. graecum. Just coming into their own also are the autumn flowering Colchicum species. All the geophytes are plunged into a sand plunge and topped off with a fine grit. They have recently been displayed into areas of origin such as South Africa, the Mediterranean, andN. America.


Over the last month some remedial maintenance has had to be carried out on the plunge beds as the concrete slab flooring was not proving strong enough to hold the several tonnes of sand. This has required the alpine team to decant the beds and remove all the sand in order for the contractors to have access to rectify the situation. We are halfway through this work and hope to remake the western plunge display very soon.


Tamping out the sand plunge bed

The western plunge beds are thus sadly bare at the moment but will soon once again house such alpine specialities as Androsace vandelii, Ranunculus calandrinioides and Dionysia involucrata. Also displayed here, when at peak interest, are our National Collections of species Tulipa, and European Saxifraga.


 A final word about our sworn number one enemy in our Mountains House - the dreaded vine weevil. This year many seemed to take cover under the protection of the lush foliage of Campanula fragilis. These and more have been actively searched out and any adults removed and destroyed as necessary. The larvae we try to control with a bio-control drench of a nematode (Heterorhabditis bacteriophera) during the warmer summer months.


We hope this gives you glimpse of what we may grow in the Mountains House and we will certainly revisit the House in future blogs

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