PRACTICAL BOTANY for GARDENERS ACANTHUS bear’s breeches PRACTICAL Geoff Hodge is a gardening and horticultural writer living in Peterborough, BOTANY UK, and the former gardening editor for Gardening News. His most recent books include The RHS Allotment Handbook, RHS Propagation Techniques, and RHS Pruning & Training. The University of Chicago Press, Chicago 60637 The University of Chicago Press, Ltd., London © 2013 Quid Publishing All rights reserved. Published 2013. Printed in the United States of America GARDENERS 22 21 20 19 18 17 16 15 14 13 1 2 3 4 5 ISBN-13: 978-0-226-09393-2 (cloth) Over 3,000 Botanical Terms ISBN-13: 978-0-226-09409-0 (e-book) Explained and Explored DOI: 10.7208/chicago/9780226094090.001.0001 Library of Congress Cataloging-in-Publication Data GEOFF HODGE Hodge, Geoff, author. Practical botany for gardeners / Geoff Hodge. pages ; cm Includes bibliographical references and index. ISBN 978-0-226-09393-2 (cloth : alk. paper) — ISBN 978-0-226-09409-0 (e-book) 1. Botany—Popular works. 2. Gardening. I. Title. QK50.H63 2013 580—dc23 2013025538 ∞ This paper meets the requirements of ANSI/NISO Z39.48-1992 (Permanence of Paper). PRACTICAL BOTANY for GARDENERS Over 3,000 Botanical Terms Explained and Explored GEOFF HODGE The University of Chicago Press Chicago and London Contents How to use this book 6 CHAPTER 2 GROWTH, FORM, AND FUNCTION A short history of botany 8 Plant growth and development 44 Buds 51 CHAPTER 1 Roots 56 THE PLANT KINGDOM Stems 62 Algae 12 Leaves 66 Mosses and liverworts 14 Flowers 71 Lichens 18 Seeds 74 Ferns and their relatives 19 Fruit 78 Gymnosperms: conifers and their relatives 22 Bulbs and other underground food storage organs 82 Angiosperms: flowering plants 25 Monocotyledons versus dicotyledons 28 Plant naming and common names 29 CHAPTER 3 Plant families 31 INNER WORKINGS Genus 34 Species 36 Cells and cell division 86 Hybrids and cultivars 39 Photosynthesis 89 Plant nutrition 91 Nutrient and water distribution 96 Dahlia × hortensis, Plant hormones 98 dahlia CHAPTER 4 REPRODUCTION Vegetative reproduction 102 Sexual reproduction 110 Plant breeding—evolution in cultivation 118 CHAPTER 5 THE BEGINNING OF LIFE Development of the seed and fruit 124 Seed dormancy 125 Seed germination 126 Sowing and saving seeds 132 Seed saving 134 4 CHAPTER 6 EXTERNAL FACTORS The soil 138 Soil pH 144 Soil fertility 145 Soil moisture and rainwater 148 Nutrients and feeding 152 Life above ground 153 CHAPTER 7 PRUNING Why prune? 160 Pruning trees 164 Pruning for size and shape 170 Aloe brevifolia, short-leaved aloe Pruning for display 172 Index 220 CHAPTER 8 Bibliography 223 BOTANY AND THE SENSES Credits and websites 224 Seeing light 178 Sensing scent 184 Scent as an attractant 185 BOTANISTS AND BOTANICAL Feeling vibrations 186 ILLUSTRATORS Gregor Johann Mendel 16 Barbara McClintock 32 CHAPTER 9 Robert Fortune 54 PESTS, DISEASES, Prospero Alpini 60 AND DISORDERS Richard Spruce 76 Insect pests 190 Charles Sprague Sargent 94 Other common pests 194 Luther Burbank 108 Fungi and fungal diseases 198 Franz and Ferdinand Bauer 116 Viral diseases 203 Matilda Smith 130 Bacterial diseases 205 John Lindley FRS 150 Parasitic plants 207 Marianne North 168 How plants defend themselves 209 Pierre-Joseph Redouté 182 Breeding for resistance to pests and diseases 214 James Sowerby 196 Physiological disorders 215 Vera Scarth-Johnson OAM 218 boTANY for GARDENErs How to use this book otany for Gardeners is written for those botanical look at pruning (chapter 7). Chapters 6 B interested in gardening with a desire to dip and 9 move beyond the realm of botany into the very a toe into the science behind plants. The science is closely related subjects of soil science, plant pathology, kept at a level so as not to be indecipherable, and any and entomology. Botany for Gardeners is not designed botanical language used is always qualified with an to be read in any particular order, rather each chapter explanation. Furthermore, the author and editors have is almost a subject in its own right, and where been careful never to stray too far from the interests of information touches on that of another chapter, the practical gardener, and as a result many examples clear cross references are supplied. used to illustrate the text come from plants that a Periodically through the book, the lifetime gardener might know, and might even have grown achievements of various botanists and botanical themselves. “Botany in Action” text boxes can be illustrators are introduced. This serves to remind found throughout the book and highlight informa- the reader of the historical context of botany, and the tion that is of particular practical interest to gardeners. debt gardeners owe to the pursuits of plant scientists The book is structured into nine chapters, each over the centuries. The fifteen botanists chosen are dealing with an important area of botany relevant to not intended to be a definitive list by any means— gardeners. Consequently, there are chapters on the the history of botany is populated by a huge number plant kingdom and plant naming (chapter 1), seed of fascinating characters who made equally fascinating germination and growing (chapter 5), as well as a discoveries and sometimes struggled to have their ideas accepted. Botany is a subject that deserves further study. While Botany for Gardeners is intended to inform gardeners, the practical examples and practical advice given are not intended to be comprehensive. Readers will find many pests and diseases discussed in chapter 9, and some suggested treatments; likewise, in chapter 6, many pruning cuts are described. Gardeners wishing to explore the practical side of these subjects in more detail are advised to read further afield. It is hoped that this book will inspire a greater understanding of the subject and a lifetime of informed gardening. Prunus persica, peach Prunus is a large genus of ornamental and edible plants, including cherry and plum. The species name persica refers to Persia (now Iran). 6 how TO USE This booK BOTANY FOR GARDENERS GROWTH, F ORM AND F UNCTION Heartwood Cambium MAIN PAGES confused because of their similarly shaped leaves, but Getting woody with Sapwood they are distinguished by their buds: alternating in secondary growth Liquidambar and opposite in Acer. If it weren’t for its opposite leaves, the Sydney red gum (Angophora As stems age, the vascular cells divide laterally to cause All nine chapters are led by the content of these ) of eastern Australia could be easily confused radial growth, leading to an increase in circumference. costata Phloem with the many Eucalyptus trees of the same region. Secondary xylem is produced to the inside, and secondary phloem to the outside. Secondary xylem cells core pages. Clear introductions and category Stem internal structure produce wood, and the seasonal variations in growth seen in deciduous trees create the yearly tree rings. Imagine a young or non-woody stem, cut across its The secondary phloem does not become woody and headings make the text easy to understand, while width as if by a pair of secateurs. The cut surface will the cells remain alive. But between the phloem and show a readily identifiable outer layer, called the epidermis a corky layer of cells begins to appear, Xylem annual growth ring Bark epidermis, and within this – unseen to the naked eye forming a ring. A water-repellent substance called accompanying plant illustrations are annotated – lies a ring of vascular tissue, made up of vascular Magnolias are either grown suberin is deposited in the cork cell walls, forming the parenchyma cells, or through thickening meristems, bundles. At the pithy centre of the stem and around as multi-stem shrubs or as bark and providing strength and reducing water loss. derived from the apical meristem (growing tip). single-stemmed trees. the vascular bundles lies a region of parenchyma tissue. Lenticels are breaks in the cork layer, made up of loose They either produce no secondary growth or, in the The epidermis covers the outside of the stem cells; they allow the passage of gasses and moisture, case of bamboos, palms, yuccas and cordylines, ‘anoma- with both Latin and common names. and usually functions to keep it waterproof and layer of each vascular bundle and is used for transport- and are clearly seen on the bark of many cherry trees lous’ secondary growth. If the dead wood of any of protected; some gas exchange may be able to take ing dissolved organic substances (such as nutrients and (Prunus) as distinctive horizontal markings. Suberin is these plants is compared with that of any deciduous place through it to allow the cells within to respire plant hormones). Sometimes when a stem is cut you produced in abundance in the bark of the cork oak tree, for example, there is a huge difference: it is less and photosynthesise. The vascular tissue serves to can see droplets of moisture collect in a peripheral ring, (Quercus suber), from where it derives its name. dense and much more porous. transport water and nutrients around the plant, and which shows the position of the vascular tissue. Because of the scattered arrangement of the as the cell walls are thickened it gives structural The main exception to this stem anatomy is found vascular bundles in monocotyledons, they grow in a support to the stem. in monocotyledonous plants, where the vascular different way. While radial growth is still possible, the BOTANY IN A CTION Vascular bundles are made up two types of vessels: bundles are scattered throughout the stem rather than larger monocots (like the palm trees) increase their xylem and phloem vessels. The xylem is found on the in a peripheral ring.