Rock gardens: how to make and maintain them

Preface

A WORD of introduction seems needed to explain the purpose of this book. No branch of horticulture at the present time occupies so much general attention as rock-gardening. Yet not a single book deals with the subject of the cost, which I have attempted to estimate, basing it on my own practical experience. It is superfluous to observe that I have not aspired to any literary graces, but merely to tell simply what I believe to be needed.

My aim has been to provide a practical volume which will enable anyone to make and plant a rock garden. When making my own, I know what I had to find out for myself, and in the following pages my endeavour has been to save others the trouble. If I may occasionally seem to repeat myself, it is because I wish viii PREFACE

to emphasise more clearly the salient points of my subject. A rock garden is one of the most fascinating of possessions. It is an inexhaustible mine of pleasure ; it entails no heavy labour, and is within the most modest means. If others derive half the enjoyment from their rock gardens that I have from mine, they will be abundantly repaid for any trouble they may take. Should I be of use to any unknown reader, I trust he will not hesitate to write to me, as I shall be delighted to reply to any questions he may care to put.

My warmest thanks are due to Mr Frederick W. Moore, Curator of the Royal Botanic Gardens, Glasnevin, who not only assisted me throughout by his kind advice, but also for ushering in my book. A preface from an acknowledged authority of his renown dignifies my own modest effort and gives it an importance to which it could not otherwise aspire. I am also deeply indebted to Mr W. Irving, of the Royal Botanical Gardens at Kew, for so kindly checking the lists of plants at the end of the book. Passed by him, they can be safely commended both to the novice

PREFACE ix

and to the more experienced owners of rock gardens. Grateful acknowledgments must also be made to Mr F. W. Moore and Mrs Delves - Broughton, who have so graciouslygiven me photographs, and to the Editor of the Ladies' Field for kind permission to reproduce some of them.

LEWIS B. MEREDITH.

Introduction

Literature treating of gardens and of gardening has been offered in plenty to garden lovers in recent years. It may fairly be said that much of it had better have been left unwritten, as it really has served no useful purpose, and has only tended to confuse rather than to assist novices, or even those with some experience of plants and their requirements. Such strictures cannot apply to this volume. It is a practical work, written by a practical man about a subject which he thoroughly understands, and by one who has experienced all the joys and sorrows connected with the cultivation of rock plants and alpines. The rock garden is no longer a feature to be found only in large establishments or in Botanical Gardens. The pleasure which is derived from the successful xii INTRODUCTION

cultivation of miniature gems and of dwarf alpine plants is now fully recognised, and rock gardens have become a popular feature in gardening of to-day. In a properly constructed rock garden many little plants which refuse to grow and live under the ordinary conditions of an herbaceous border, and which resent the aggressive attentions of their more robust neighbours, generally demonstrating their resentment by dying, can be cultivated and kept in health and vigour for many years, protected by stones, sheltered from drying winds, and from shade or sunshine, dryness or moisture, according to their requirements. They can, owing to their raised position, be seen and tended in a manner more conducive to the comfort of the observer and cultivator than would be possible if they were grown on the flat.

To ensure even moderate success in rock gardening two main points are essential : a properly constructed rock garden, and a reliable guide to the nature and requirements of plants to be grown on it. There existed a demand for a sound practical work, giving explicit and detailed information on these

INTRODUCTION xiii

points, and this volume meets it. Mr Meredith writes with practical experience. His own rock garden, constructed by himself, is artistic in conception, covers a considerable area, and suits the requirements of a large and varied collection of all classes of alpines. In it many difKcult subjects, such as Edrianthus Pumilio, Morisia, Androsace Sarmentose, Carnea, Villosa^ Saxifraga retusa^ aretioides^ casia, Diapensoides, Daphne cneorum and Blagayana, flourish and grow into good-sized tufts.

The details of how this success has been achieved are fully explained, concisely but clearly, and all necessary information is given. F. W. MOORE, M.A., A.L.S.

Part I Chapter I

Surroundings — What to avoid — Objections to trees —Aspect — Contour — Nature of soil — Chief points to be noted — Typical site

Chapter II

The natural — The artificial — Types of the natural — The old quarry — The amphitheatre — The horseshoe — The valley — The cliff — The rocky bank — The rocky knoll — Points to be noted — Types of the artificial — The sunken — The gravel- pit — Bank and knoll types — The rocky bed — The very large rock garden — Advantages and disadvantages of the natural — Advantages and disadvantages of the artificial

CHAPTER III First preparations — Cleaning ground — Exposing and

preparing the rock — Pockets natural and artificial 32

Chapter IV

What can be done with a level field — Laying out the garden — Boldness of design — Preparing banks xvi CONTENTS

FACE

for rockwork — Treatment of natural valley — Formation of banks — Example of a " valley " garden — Points to be noted in excavations — The hollow garden — Gradient of slopes — Drainage — Aspect — Bank and knoll types and their treatment — Rock bed — Very large rock garden — Difficulties connected w^ith this type of garden — Points to be noted in artificial rock gardens ....... 3^

Chapter V

Kind of rock to use and w^hat to avoid — Principles of particular construction — Types of rockw^ork to avoid — The placing of individual rocks — Fissures and how to make them — Strata — Principles of general construction — Paths — Steps — The moraine ....... 64

Chapter XI

Climatic difficulties — Contrasting natural and artificial conditions — Tendency to loss of characteristic growth — Methods of overcoming climatic difficulties — Importance of proper planting — Time to plant — Importance of top-dressing in spring — Weeding — Garden pests and how to|fdeal with them . . . . . . -155

Chapter XII

Points for consideration — Difference between alpines and rock plants — Grouping — Examples of same — Planting bulbs — Ferns — Caution against rampant-growing plants — Importance of proportion — Planting shrubs . . . .183

XVlll

CONTENTS

Chapter XIII Cost

Points affecting the cost — Labour — Clearing scrub — Drainage — Estimated cost of rocks, sand, etc. — Cost of making artificial bog garden — Cost of plants ........

PART II Alphabetical list of plants suitable for the rock garden 215

A selection of plants for dry and sunny positions, and

time of flowering ...... 369

A selection of plants for full sun or partial sunny

positions, and time of flowering . . '370

A selection of plants for positions in deep shade . 371

A selection of plants for partial shady positions. . 372

A selection of plants for moist positions in sun or

A selection of plants suitable for trailing over rocks . 373

A selection of dwarf shrubs, pines, and conifers . 375

A selection of hardy ferns suitable for rock garden in

sun or half shade . . . . . -376

A selection of hardy ferns for shady position . -377

A selection of bulbous plants . . . . -377

Plants for massing . . . . -379

LIST OF ILLUSTRATIONS

Rock Garden and Stream, Mount Usher Frontispiece

Valley Type .....

„ „ Portion of Author's Garden

Knoll Type .....

Bank Type. (In course of construction)

,j „ (Site being cleared)

„ „ (Rocks in place)

Rocky Bed . .

Haberlea rhadopensis

The Bank. (Roughly formed before rocks are put into place) .

First Line of Rocks laid

Second Line of Rocks in Position .

rockwork advancing up the hill .

Nearing Completion

The Complete Rockwork

Example of Rockwork

14 20 20 22 22 26 26

40 40 50 50 58

58 64 64

XX

LIST OF ILLUSTRATIONS

Bog Garden in Author's Rock Garden

Water-Lily Pond, Mount Usher .

Water Garden .....

Part of Wall Garden, Mount Usher .

Dianthus alpinus .....

Romazoffia sitchensis ....

Saxifraga apiculata ....

Saxifraga oppositifolia ....

Androsace lanuginosa, in the Author' Garden ......

IIO

120 176 176 184 184

PART I

Chapter I

Surroundings — What to avoid — Objections to trees — Aspect — Contour — Nature of soil — Chief points to be noted — Typical site.

"Where shall I lay it out?" This is the first of the many problems to confront one who intends to become the happy possessor of a rock garden. In some cases this unfortunately presents but few difficulties — unfortunately, I say, for then the ground that is available, frequently not of the most suitable, is so limited that there is little, if any, choice in the matter. But others, who have a greater variety of positions to select from, will need to give the question more careful consideration. Therefore it would be a mistake to lay down any hard and fast rule as to where the site should or should not be, for this must obviously greatly depend on what choice of positions there is.

A rock garden can be made almost anywhere — almost, be it emphasised ; for under certain conditions, which I shall point out later on, the chances of success would be but small.

But no matter what the position is, whether the spot selected be the most ideal, or the most unpromising, it will require considerable thought and no little skill to lay out the garden to the best advantage.

The object of this book is to help the reader to approach as near as circumstances will allow to the ideal rock garden : that earthly Paradise, which, alas ! the skill of mortal man has not yet achieved, nor ever will, I fear.

Though there is a great difference of opinion as to what this lovely spot should be like, at the same time there are many points on which all agree. Some indeed are absolutely essential to the well-being of those alpine gems, which one hopes to see grow and thrive as they do in their natural home, though too often one is doomed to disappointment. Yet be not discouraged, for there are many and lovely plants which are not in the least difficult to cultivate, and which will amply repay the care devoted to them. But two conditions they do require, light and pure air, which, as with all plants, are essential to success, and indeed I may add a third, sufficient drainage. One has only to remember where most of these treasures make their home in order to realise how important these factors are.

Let us for a moment imagine ourselves on some mountain slope where the alpines are in their natural state ; where the Androsaces and Saxifrages carpet the boulder-strewn ground, or beautify the weather-beaten rock with their dainty loveliness ; where by the tiny stream can be seen the lovely Soldanellas and Ranunculus and a thousand other plants to delight the heart of man. Standing there, gazing around, what a picture meets the eye ! The craggy height above ; below, the wind-swept pines ; and, far as the eye can reach, range upon range of mountains with their eternal snow-capped peaks glistening in the sunshine. Here is no jarring note ; all is peace and quiet. Nowhere has the hand of man marred the beauty of the landscape. We see Nature as she is.

With this picture in our minds let us see how best to apply the lesson it has taught us.

First we learn that the rock garden should, where possible, be out of sight of all stiff surroundings ; out of sight of the formal garden, with its trim beds and smooth lawn, its close-clipped hedges and rose-clad walls, in some quiet and secluded spot merging from the shrubbery or wild garden. At the same time let it not be so far from the house as to prevent us snatching odd moments amongst our treasures to see what flower has at last bloomed out, or what special plant was raided by the slugs last night.

As variety of outline is one of the keystones of success, endeavour to select a spot that will afford this with the minimum amount of labour.

As the spots to choose from are so many and varied, perhaps it would be best, first of all, to find out what should be avoided and what conditions would militate against success.

The worst and perhaps really the only hopeless site is one with large overhanging trees ; for the drip from their branches would all too soon prove fatal to the plants underneath. Although there are some plants that will live and even thrive beneath trees, they are not sufficiently attractive to cultivate exclusively. So to choose such a spot would be but to court disaster ; and in addition to the damage caused by the drip from the branches, the roots of the trees would very soon exhaust the soil that had been so carefully prepared for the alpine treasures. It would surprise many to find to what a distance these roots extend. So, above all, let there be no trees overhead, and, if possible, none within at least 1 5 yards — this is the minimum, — and then only to the north and west. On the other points, south and east, they should be still further away — at least 30 yards, — and even at that distance, as few of them as possible. For if they are closer, the air, which all plants so urgently require, will be shut out, and part at least of the garden will be in constant shade during the winter, with fatal results to many of the plants. Therefore, when feasible, choose a position where there is no chance of trees intercepting the low winter sun, for this is more valuable when the days are short than during the summer months.

In cases where, owing to unavoidable circumstances, the trees on the north and west are rather close, provided there is no drip on the garden from their branches; much may be done to overcome the root trouble. A narrow trench sunk rather deeper than the roots of the trees descend, and filled with rough concrete, will form an effectual barrier.

Now, having decided that the site must not be overshadowed nor shut in by trees, the next point to be considered is the aspect.

This is all-important. The problem is to find out at what point sufficient, but not too much, sunshine can be obtained with due regard to shelter from cold winds. A spot should be selected having an aspect as nearly as possible south-east ; and if there be a wood or a belt of trees some distance off" on the northwest, so much the better. This aspect will give the maximum amount of the winter's sun, and, as south-west is theoretically the hottest point, the rock garden will not be so liable to be burnt up during the summer.

The next point to be investigated is the contour of the land, and on this will depend to a great extent the type of rock garden to be constructed.

Sloping ground, undulating if possible, is undoubtedly the best, for thus more pleasing effects can be obtained, with less labour and expense, than can be expected on level ground, and the fact that the drainage can be made more effective is by no means the least important consideration. Hollows should at all times be avoided when there are any difficulties in the way of draining them effectively. Nothing is more fatal to alpines, and indeed to all plant life, than stagnant moisture, which so quickly makes the ground sour.

The nature of the soil should be also taken into account. It is a great mistake to imagine that rock plants do not require good soil ; the very best fibrous loam, the deeper the better, with a light sandy subsoil, is what they delight and revel in. Therefore, in the selection of a site, avoid as far as possible anything in the lo ROCK GARDENS

nature of a heavy clay soil in which it will be found difficult if not impossible to grow many of the choicer plants, and which will require more drainage and be always hard to work, whether in very dry or wet weather. A stream should be brought through the garden, if it can be obtained by fair means or foul. The merest trickle will suffice, so long as it is constant, but constant it must be, and it will add tenfold to the charm of the garden and afford unlimited possibilities.

Having fully described the chief conditions favourable and unfavourable in selecting a site, I briefly recapitulate them as follows : — The garden, when circumstances will permit, should be away from and out of sight of anything formal, approached through the wild garden or shrubbery, but still within reasonable distance of the house ; the ground should be undulating, with good light fibrous loam, facing south-east, with, when possible, a stream ; but, most important of all, it must be free from encroaching or overshadowing trees and have plenty of air and sunshine.

Bearing these points in mind, a typical

THE SITE II

position for this would-be garden of delights may be considered. Perhaps at the foot of a nicely wooded hill facing south-east, with undergrowth around, there may be some open spot, the extent of which is not altogether important ; by removing some shrubs and perhaps a few trees, it can be enlarged, if too small, and, on the other hand, if too big, it will afford scope for judicious planting. This open ground may be in the form of a little valley sloping up the hill, or, again, a small prominence thrust out from the surrounding and gradually rising ground, or undulating with natural hills and hollows. Or, perhaps, the site could be a miniature gorge with wooded heights on either side and a stream flowing through it. These are indeed ideal positions from which to select, provided always that they afford sufficient air and sunshine.

But with far less promising material — for instance, a sloping field, or even a level one — much can be done. The former is by far the better of the two, for on level ground the question of drainage would probably arise and cause serious difficulties.

Sunken ground in the form of a large hollow, such as an old sandpit, can be utilised to some advantage, as can also an old quarry. These, if wooded above, will make charming sites ; but here again attention must be given to the essential necessity of obtaining sufficient fall for the drains. On that point let there be no uncertainty, for, if the drains prove defective, but a poor return will be made for time and money expended.

The foregoing are, I think, a few of the most usual sites to select, and their description will, I hope, suggest to the reader how to make the best choice of the ground he has at his disposal. What form the garden will eventually take, and how it can most advantageously be laid out, will in a great measure depend on such details as soil, locality, contour of ground, money to be expended, etc. All these will be dealt with in the following chapters.

Chapter II

The natural — The artificial — Types of the natural — The old quarry — The amphitheatre — The horseshoe — The valley — The clifF — The rocky bank — The rocky knoll — Points to be noted — Types of the artificial — The sunken — The gravel-pit — Bank and knoll types — The rocky bed — The very large rock garden — Advantages and disadvantages of the natural — Advantages and disadvantages of the artificial.

The different types of rock garden may be divided into two sections, which can be called the natural and the artificial.

In the Natural garden the rocks are already placed there by Nature, and all that is required is to utilise them to the best advantage.

In the Artificial garden — the name speaks

for itself — the rocks have to be placed, and in

some cases even the banks on which to lay

them have to be formed.

In the first section, the Natural, there are three types — the old quarry, the rocky bank, and the rocky knoll.

The second section is more varied, and in it may be included the sunken garden, the old gravel-pit, the bank, the knoll, the rocky bed, and the very large rock garden.

The old quarry^ a favourite and very charming site for a rock garden, and one that has many points to recommend it, is hard to deal with owing to the difficulty of adorning the large masses of perpendicular rocks, which, although capable of giving very striking effects with their cataract of flower and foliage, require years of growth even under the most favourable conditions. It usually takes one of four forms, which may be called the amphitheatre, the horseshoe, the cliff, and the valley.

First let us note the amphitheatre^ a very uncommon type. This formation, as the name would imply, is a hollow almost or entirely surrounded by rocky sides, and will seldom be a really suitable site. Most probably it will be found very difficult to drain thoroughly, and even were this done, there would still be that

VALLEY TYPE.

VALLEY TYPE. PORTION OF AUTHOR'S GARDEN.

( Veronica Lavaudiana and Atibrieiia Dr Meeles in foreground.)

want of air which causes plants to damp off, especially during the winter. The only occasion on which this form of quarry is admissible is when it is on a very large scale, at least 25 yards across, and even then it will generally prove but a doubtful success.

The next and perhaps the commonest form is the semicircle or horseshoe, usually an excavation into the side of a hill, giving bold rocky places for planting. This is an excellent form to choose, provided it fulfils certain conditions. It should not open towards the north, for then it would be exposed to the cold winds and the greater part of the rocks would constantly be in shade, and although some shady corners will be found useful, the majority of plants like the sun. In fact, any point but this will do, for so long as the entrance is sheltered from the north it is a matter of no great importance where it may be ; but the south-east is preferable, for it gives greater variety of position, both for sun- and shade-loving plants.

The valley or defile form can be made very effective. The best way for it to lie is east and west, but this is not so important provided that its course winds sufficiently. The more it winds the better, for it then provides the greatest variety of aspects and sheltered and shady nooks, the advantage of which will be duly appreciated when the time comes for planting. It will also be beneficial if the bottom of the valley slopes gradually from one end to the other, thereby ensuring more efficient drainage. A stream down the centre, when it can be obtained, greatly enhances the charm and considerably enlarges the scope for variety in plants that can be cultivated, because those preferring moisture can be planted on its banks, and those requiring a dry soil will find a home on the heights above.

The cliff type, as the name implies, is of abrupt formation, rising from comparatively level ground, and is one of the best and most effective forms, provided the aspect is suitable. South-south-east is the best, but any other point will do so long as it does not face towards the north, for with a northern aspect the garden would get but little sun, certainly not the amount all alpines so imperatively require.

In this type the surroundings should be carefully noted, so that they may be in keeping with the proposed rock garden. The ideal approach is through some open and undulating stony ground, with occasional patches of stunted gorse and heather, dotted here and there with oak, holly, or birch trees ; then a stretch of grassy sward, with occasional rocks, which become more numerous as the slope gently rises towards the foot of the clifF. Even this is a delightful scene ; but picture the face of the rock, now bare, clothed with sheets of Aubrietias, Rock Roses, Dianthus, and innumerable other equally lovely plants, the Silver Saxifrages springing from some almost invisible chink or cranny, and nestling close to the rock, with their airy blooms waving in the breeze, while from some shady nook the Ramondias peep forth. This is indeed a delightful picture, therefore care should be taken to see that the frame is worthy of it.

There are now a few points to be noted which apply equally to all the foregoing forms of garden made from an old quarry.

The first and most important is to observe the state of the quarried face of the rock. By this is meant, whether it is much broken in outHne or presents a sheer, perpendicular face. It should be rough and jagged, so as to give a number of ledges — the more numerous they are and the greater their variety the better — forming steps or terraces, by which easy access can be had to all parts. Otherwise it will probably be necessary to plant the alpines and examine them from the steps of a ladder, which, to say the least, is not desirable. But, bad as a too smooth surface may be, an overhanging rock face is even worse. An odd protruding ledge here and there does not so much matter, in fact they may prove of service, but even they should not be of sufficient size to prevent the rain from reaching the plants below. The whole tendency of the rock should be to slope back from the ground at the foot, for it is necessary that rain should have access to every part. Though it is wonderful in what apparently dry and arid spots alpines will thrive, it is certain that their roots must find moisture somewhere. Few people realise to what an extent rocks retain moisture even during a dry season, so it is important that the slope should be sufficient to catch and store the rain. If it is intended to conduct a stream through the garden, make sure the outlet will be such as to prevent any risk of the garden suffering from flood.

The next type is the rocky bank. This, as its name would imply, is a bank of natural rock, and may be the face of a small hill, or form part of a large one.

It is, in fact, rather similar to the quarry cliff, already described, except that the rock, being as nature left it, will probably have a more gradual slope, and therefore possess the advantage of being easier to clothe.

The advice as regards surroundings applies equally here. The rock garden should be approached through shrubbery or wild garden, and situated in some open, though not too exposed, spot facing south-east, with a background of suitable trees, such as oak, holly, or birch, or any of the Conifer family.

The rocky knoll is the next and the last of the natural types. It may be a small eminence of rocky ground standing out by itself, or a sort of promontory on the side of a hill, or on sloping ground.

This type is practically identical with the last described, except that in this case the whole or the greater part of the hill is dealt with, whereas in the former only one face of it was. The knoll is undoubtedly the better of the two, for with it a much greater variety of aspects can be obtained, and also more scope for developing the different natural undulations of the ground. The aspect is, of course, unimportant, for a hill standing by itself will be open to all points of the compass ; and even if it be part of a larger hill, it will be shaded only on one side, which will not so greatly matter. With this type, also, care should be taken that the surroundings are suitable.

As this concludes the types of the natural rock gardens, a few points in connection with them may be mentioned before proceeding to the artificial.

In the first place, large masses of rock have to be dealt with as placed by Nature's allpowerful hand, and we must therefore adapt ourselves to whatever conditions we may find.

KNOLL TYPE.

BANK TYPE.

(In course of construction.)

Since the chief object is to provide as many spots as possible to plant in, select the type of rock that will give the greatest variety of pockets, remembering at the same time that all pockets, no matter of what size, must be able to be drained. The necessity of draining having already been emphasised in the first chapter, it is superfluous to dwell further on it here.