Managing Plant Collections Report

Contents

Section 1. Introduction

1.1 The Brief Page 2

1.2 Report objectives Page 2

1.3 Description of the site Page 3

Section 2. Suggested introductions

2.1 Profiles of suggested introductions Page 5

2.1.1 Alnus, Salix and Populus profiles Page 5

2.1.2 Profiles of under planting species Page 14

2.2 Explanation of selected plants and evidence supporting choices Page 21

Section 3. Evaluation of specimens currently on site

3.1 Accessions to stay Page 23

3.2 Proposed removals Page 25

3.3 Proposed landscaping Page 26

Section 4. References Page 27

1. Introduction

1.1 The Brief

"Management at RBGE wish to extend the collection of Alnus, Salix and Populus spp and to display them in a more natural/ecological setting under-planted in suitable areas with appropriate herbaceous plants.

The current proposal is that this new collection will be established within Garden Area K02. The site and collection will form part of the general public display area in the Garden and provide material of interest to the amateur and professional horticulturalist alike as well as scientific staff studying the biology, conservation and taxonomy of the genera."

1.2 Report objectives

This report aims to advise on the suitability of the area K02 at The Royal Botanic Gardens Edinburgh Inverleith site for redevelopment in the manner specified in the brief. The report will suggest a cohesive list of native species which could be used to recreate a natural habitat. On the grounds that RBGE has policies in place to increase its wild collected material no cultivars will be included in the list.

The report will also make recommendations as to any required removal or relocation of existing trees on the site after considering their value to the garden; taking into account historical links (i.e. collected by a famous plant hunter), aesthetics, origin of material and if they are likely to be damaged or disturbed leading to death during the redevelopment.

The report will look at what conditions Alnus, Salix and Populus need to grow successfully and if the suggested site can provide this for them or could be made suitable. It will also look at which species have good stories for interpretation, are currently of scientific or conservation interest and have growth habits which compliment each other. It will finish with an outline of how the area could be landscaped to best display the new planting.

1.3 Description of the site

The Garden is located in the south east of Scotland and has a maritime climate, is at an elevation of 20-40m above sea level and has an annual rainfall of 637mm.

The bed itself is reasonably level and sheltered by surrounding tree canopy. It has a predominantly mature canopy with virtually no wild collected material and only 6 recent plantings, there is a gap in the canopy; where the mature specimens that are currently on site will die and there will be no semi-mature trees to take their place. There is no theme to the selection of trees in the bed, it seems like bits and pieces have just been added in over the years. Presumably because there was no plan for the bed there is no interpretation.

View from the north east corner of the bed.

Water runs off the Chinese hillside extension onto the site and just beyond the east edge of the site the ground drops away to a pond fed by a natural spring. The bed is surrounded by soak away drains (a pit filled with gravel) there is no other drainage in place. These factors combine to make it a very damp site which is useful for the cultivation of Alnus, Salix and Populus. Apart from trees the site is currently covered with closely mown grass. It has surface compaction and is waterlogged in the north east corner. The whole garden is on a raised sand bed, hitting sand at two spades depth. No soil pits have been dug to investigate further; local records and knowledge were used. There are no overhead services, limited underground services and there is clear.

Water lying on the surface in the north east corner.

Given that it is already a wet site that has a disjointed, aging population of non-wild origin trees and is easily accessible this report recommends that K02 is perfect for redevelopment to bring it in line with the Garden's aim of showing plants in a more natural setting. Creating a more natural environment with Salix, Alnus and Populus and working with a site that is already somewhat predisposed to suit their needs will hopefully lead to increased biodiversity with thriving populations of unplanted but welcome bryophytes, insects, invertebrates and more. Having a theory behind the planting will make it possible to have meaningful interpretation, this site could be turned into a star attraction in the garden for education, research and for visitors who just want to walk through something pretty.

2. Suggested introductions

2.1.1 Plant profiles of native Alnus, Salix and Populus.

Scientific name: Alnus glutinosa

Family: Betulaceae

Common name: Alder

Description: Fast growing tree up to about 21m tall, girths of up to 4.3m but often appears as a shrub. Said to be mature at 60 years with a lifespan of 150. Dark glossy leaves, male and female catkins on same tree; the female catkins look like small cones

Distribution Native to Britain and Europe, all the way down to North Africa and eastwards towards Siberia.

Habitat: Grows on wet or flooded sites, often next to streams,