Forestry Commission ARCHIVE FORESTRY COMMISSION BULLETIN No. 59 SEED MANUAL FOR ORNAMENTAL TREES AND SHRUBS by A. G. Gordon, B.Sc., Agric., Ph.D. and D. C. F. Rowe, B.Sc. LONDON: HER MAJESTY’S STATIONERY OFFICE © Crown copyright 1982 First published 1982 ISBN 0 11 710152 4 CONTENTS Part I: Seed Biology Page 1 Seed Source—Collection or Purchase 3 2 Forest Seed Legislation . 5 3 Seed Formation 7 4 Seed Collection and Processing 13 5 Seed Storage . 2 0 6 Seed Testing and Sowing Density 23 7 Seed Dormancy and Pretreatment 35 Part II: Tables of Data and Recommendations Notes on presentation of data and recommendations 51 1 Classification, nomenclature, and natural distribution, charac­ teristics and recommendations for planting ornamental tree and shrub species. I n d e x .......................................................................... 52 2 Height, seed bearing age and seed crop frequency of ornamental tree and shrub species ........ 80 3 Phenology of flowering, seeding and collection information for ornamental tree and shrub species ...... 8 6 4a Seed yield data 98 4b Seed/fruit collection and processing sheet 1 0 0 5 Summary of storage data and recommendations 1 0 2 6 a Seed quality data 104 6 b Recommended germination temperatures 116 6 c Sheet for assessment of seed quality in the nursery 117 6 d Nursery record sheet 118 7 Recommended seed treatments before sowing 1 2 0 Sources of data 129 iii Introduction The Forestry Commission has, until recently, restric­ It was felt that a manual of this sort would be ted its broadleaved tree seed research to a very small incomplete without some recommendation as to number of species important to the commercial where the species covered should be planted. forestry industry. However two factors have brought Accordingly a summary of the recommendations about a change, firstly a shift in Commission policy made by Alan Mitchell and John Jobling in the towards more amenity and environmental planting book entitled Decorative Trees for Town and Coun­ and secondly a desire in many trade nurseries to try soon to be published by HMSO has been improve on the poor production record from seed included. For tree species and shrubs not covered by for many ornamental tree species. these authors, recommendations were drawn from The British nursery stock industry has tradition­ Brown (1972), Hilliers Manual (1971) and Notcutts ally relied heavily upon vegetative propagation. To Catalogue (1980). The recommendations are given a considerable extent this has been due to the unre­ in Appendix I along with a full list of the botanical liability of production from seed. Vegetative pro­ names, synonyms, common names and origins of pagation is the only method of ensuring complete the species covered by the manual. trueness to type, but there are many situations where The second aim of this manual is to provide the the natural variation inherent in plants raised from student and interested amateur with a complete seed will be acceptable, if not actually beneficial. scientific background to the subject of raising trees There is a paucity of published British work on and shrubs from seed, and to act as a reference the problems of propagating broadleaved species volume should they wish to pursue their interest from seed. Nurserymen have therefore had to rely more deeply. It will also act as a handbook for mainly upon foreign material much of which is anyone involved in seed collection, seed testing and outdated, contradictory and unreliable. This has storage. The manual therefore seeks to fill an often resulted in seeds being sown on an entirely obvious and important gap in the current British unplanned and uneconomical basis. Although the literature on the subject of raising trees and shrubs cost of the seed itself is perhaps relatively small, a from seeds. great deal of time and money can be wasted on This manual is divided into two parts: the first preparing and maintaining seed-beds for seeds which part describes general principles of seed biology and will never germinate. seed handling, while the second consists of tables The aims of this manual are two-fold. Firstly it giving detailed information on many aspects of seed presents the practical plant propagator with all the origin, production, quality and treatment for indi­ relevant information he needs to ensure reliable vidual genera and species. For some species data production from seed of the more commonly grown and experience are sparse and positive recommen­ ornamental broadleaved species. It includes the latest dations to ensure germination cannot be made. results of the Forestry Commission’s own work and However, these are the only results available and summarises existing information gleaned from although improved information is likely to be avail­ experienced nurserymen and the literature. This pub­ able later, present knowledge has been included for lication, therefore, updates those parts of Chapters guidance, and as a reference point for further 6 and 7 of Forestry Commission Bulletin 43 (Ald- research. hous, 1972) relating to broadleaved species and Throughout the chapters of the manual frequent replaces Forestry Commission Research Branch references have been made to individual genera and Paper 10 (Gray, 1953). It does not attempt to discuss species. These have been included by page number establishment, management and financing of nur­ in Appendix 1 to serve as a specific index. A subject series. These topics are adequately covered in Bul­ index is included in its own right at the end of the letin 43 or rather more fully in Hardy Woody Plants manual. fro m Seed (McMillan Browse, 1979). For the benefit Sessile, Pedunculate and Red oak and beech are of the practitioner the recommendations are sum­ grown as widely for ornamental purposes as they are marised in appendices 5, 6 and 7 at the end of the for commercial forestry. They are the only species manual. included in this manual that are subject to legis­ lation. They will be covered fully in a companion to Hilliers (Winchester) Ltd (1971) 2nd ed. Hilliers this, a seed manual of commercial and conifer Manual of trees and shrubs. Hillier and Sons, species, in a Forestry Commission Bulletin but for Winchester. the sake of completeness they are also included here. McMillan Browse, P.D.A. (1979). Hardy woody Students should note that throughout most of the plants from seed. Grower Books, London. 1-163. manual the term ‘seed’ is used in its broadest sense (Mitchell, A.F. and Jobling, J. (1982). Decorative to describe any prime dispersal unit of the species trees for town and country. HMSO—to be pub­ here considered comprising a food storage area, a lished). latent growth axis and a restrictive covering. The Notcutts Nurseries Ltd (1980). Notcutts catalogue exception is Chapter 3 where such lax terminology 1980 edition. Notcutts Nurseries Ltd. Wood- is unsuitable for the topic under discussion and bridge, Suffolk. where the term ‘seed’ is used literally to describe a matured ovule containing an embryo and nutritive tissue enclosed in a coat (testa) or coats (tegmen and ACKNOWLEDGEMENT testa) derived from the integument(s). Apart from the sources of data quoted the authors would like to acknowledge the help given in the preparation of this Manual by many nurseries, but in particular by Denis Fordham and Tom Wood of Oakover Nurseries, Ashford, Kent and by Andrew REFERENCES Fairweather, late of Hillier Nurseries (Winchester) Aldhous, J.R. (1972). Nursery Practice. Forestry Ltd, Winchester. The assistance given by other mem­ Commission Bulletin No. 43, pp. 1-184. bers of the Seed Branch and by members of other Brown, G.E. (1972). The pruning of trees, shrubs Branches in Research and Development Division too and conifers. London, Faber & Faber. numerous to mention, is also gratefully acknowl­ Gray, W.G. (1953). Nursery notes on broadleaved edged. Dr. Gordon would like to acknowledge the trees. Forestry Commission Research Branch time he was allowed to complete this publication Paper No. 10. pp. 1-40. after joining the Seed Unit of EFG (Nurseries) Ltd. PART I: SEED BIOLOGY 1 Seed Source—Collection or Purchase Page 3 2 Forest Seed Legislation 5 3 Seed Formation 7 4 Seed Collection and Processing 13 5 Seed Storage 20 6 Seed Testing and Sowing Density 23 7 Seed Dormancy and Pretreatment 35 Chapter 1 SEED SOURCE-COLLECTION OR PURCHASE? Once it has been decided to grow stock from seed important to see that the fruit does in fact contain rather than by purchasing it from home or foreign some fertile seed. A lot of time and expense can be nurseries, the first decision to be made is on the wasted if a collection is subsequently found to source of seed. There are two alternatives, either the contain nothing but empty seeds. The greater the set seed can be collected locally or it can be purchased of seeds in each fruit, the more seed will be pro­ from one of the commercial seed houses. Each has duced, but it is only by making personal records that merits and demerits which deserve close consider­ knowledge of what constitutes an economical collec­ ation. tion will be built up, although the tables in Part II will help. It is often tempting to collect seed from individual specimen trees in an arboretum or garden because Local collections of ease of access. It should be clearly realised that The local collection of seed has much to recommend there are dangers associated with this practice. Self it and certainly, since becoming more interested in pollination almost invariably leads to a poor set of ornamental broadleaves, the Forestry Commission viable seed. The seed produced may be less vigorous has encouraged nurserymen to collect their own and more susceptible to disease.