Alpines From The Wild To Your Garden
By Howard Drury
The growing of Alpines can be undertaken in any garden. If there is space for a rock garden then a wide range of Alpine plants can be grown. Failing this, a dry wall or scree garden may be constructed. Miniature Alpines can be grown in sinks or troughs and paving looks its best when inter-planted with a few suitable Alpines.
What is an Alpine Plant?
The term "Alpine plant" has been applied in a loose way to all dwarf plants suitable for a rock garden. All zones, from the warm temperate to the Arctic regions furnish some plants which find their way into the rock garden; for example:
Alpine Phlox from sandy soil New York to Florida
Stonecrop native to the British Isles
Anemone pulsatilla Swiss Alps
The true Alpine is restricted to those parts of the world between the limits of eternal snow and the line at which even coniferous trees cease to flourish. The altitude at which they grow varies greatly; from sea level in Arctic zones to several thousand feet in the warmer parts of the world. In the European Alps its lowest limits lie between 1500 and 2000m (5000 6500 feet.) above sea level.
What are the Natural Soil Conditions?
In the Alpine zone the physical conditions of the soil varies greatly as also does the supply of moisture. The moraines consist of boulders and stones of varying size alone or mixed with the finely ground deposits of the glaciers. The screes consist of debris fallen from mountain sides where water trickles only far below the surface.
What is the Natural Climate?
Rainfall usually increases with the height up to a point dependent upon climate and location. Above this it rapidly diminishes and the air becomes dry. Air temperature fluctuations are greater, i.e. very warm with the sun's rays by day and far colder by night. Soil temperatures are often higher than air temperatures (2 4 degrees Centigrade) at 2300m (7500 ft.). Light intensity is greater at 1800m. (6000ft.) or more and also the spectrum is different. It has more blue, violet and ultra violet light. Snow covering is common. With 1.3m (4 feet) depth of snow, freezing takes place to 0.3m depth (12 inches). With less than 0.3m depth of snow, frost penetrates much deeper than 0.3m. Melting snow in spring gives plentiful moisture and so plays an important part in the seasonal growth of Alpines.
How Alpines Adapt to Their Environment
a) Low Habit of Growth
The mat forming plants, (e.g. Saxifrage) enable them to endure exposed conditions, which would be impossible for taller growing subjects. The mat like association of shoots also confers additional protection from the drying winds and also helps to retain snow that may be necessary.
b) Reduction of Transpiration (loss of water)
Short stems, thickened foliage reduced in size, hairiness of leaves and horizontal growth all help to reduce loss of water from the plant and protect the chlorophyll (green colouring matter) from destruction by high intensity light. Examples of this are seen in:
i) The thick succulent like leaves of Sedum (Stonecrop)
ii) The hairy covering of the Edelweiss
iii) The chalk glands of encrusted Saxifrages
c) Extensive Root System
Compared with many plants, the roots of Alpines are very extensive. In their mountain homes the roots may go to a considerable depth in rock crevices etc. This ensures that a sufficient volume of soil is exploited to enable the plant to obtain an adequate amount of moisture and food. In addition, fluctuations of temperature hardly affect the root system.
Your rock garden
Many people have the misconception that Alpines will grow in any soil, however poor. This is far from the truth. With few exceptions, most Alpines require a light porous soil, rich in humus in the form of peat or leaf mould. If you are unfortunate enough to have heavy soil, every effort must be made to lighten it by digging in gravel, sand and peat moss. Raising the level of the bed will allow maximum drainage. In lower areas it may be necessary to incorporate drains. Many Alpines will flourish if given special conditions that often bewilder the beginner. These special conditions can be grouped and are briefly described as follows. (It must be said that it is impossible to "lay down the law" in any way regarding the treatment of any particular species and experimentation is often the answer).
The scree or moraine
In nature, certain mountain plants prefer to grow in specialised conditions provided by the screes and moraines caused by mountain erosion. These are made up of about 75% rock, ground up into small pieces and 25% rotted vegetation and soil. The drainage is therefore, speedy and perfect. In order to grow these plants successfully in the garden these conditions must be provided and the following indications for doing so may be helpful.
Choose a shallow slope facing south or west. If your soil is heavy dig out 18 inches and fill in the bottom 6 inches with coarse drainage material such as broken bricks etc. Cover with upturned turves or half-rotted leaves to prevent clogging of the drainage. If the soil is light and porous this extra drainage will not be required and only 12 inches need be dug out. Obtain some stone chippings (or gravel) such as is used for road making. We prefer granite chippings of about ¼-½" diameter but limestone or sandstone can be used. If limestone is used, remember you are limited to lime loving plants only. Make up a compost of roughly 50% good top soil loam, 25% peat moss or leaf mould and 25% coarse sharp sand. Mix 50% chippings and 25% of the compost mix and fill in to the top. Give the whole a good dressing of bonemeal and introduce a few well placed rocks.
This type of gardening is fascinating and becoming more popular. Choose a low bank, or make a mound, preferably facing west. Obtain blocks of heather peat, such as is used for burning and build, as if with bricks, shallow undulating walls not more than 12 inches high and preferably less, thus forming a series of irregular ledges. As the peat walls are primarily for growing peat-loving, lime hating plants, be sure to obtain acid soil for your compost. Make up a mixture of 50% good lime free loam, add 50% leaf mould or peat moss with some coarse sand added to keep it open. Use like cement when building the walls and ram firmly round the peat blocks, filling in all the ledges and beds with the same material.
Try and plant some of the low ericaceous creeping plants such as Gaultheria, creeping Rhododendrons, Cassiope, Pernettya and Phyllodoce between the peat blocks when building. This type of garden is most suitable for all dwarf ericaceous plants, the choicer Primulas, Omphalogrammas, Ourisias, Nomocharis, autumn Gentians etc. Try and pay a visit to the peat wall garden at the Edinburgh Botanic Gardens or the Northern Horticultural Society's Garden at Harlow Carr, Harrogate to see fine examples of construction and planting.
The alpine house
Many plants too small, too difficult or flowering too early in the year to grow in the open make beautiful specimens in the Alpine House. A blaze of colour can be enjoyed in the early spring. There are also many other plants, such as Lewisias, Auriculas, dwarf bulbs etc. which, although perfectly easy outside, make superb pan specimens. The perfect Alpine House is a low spanned structure with ample ventilation along the whole length of the roof. Ventilation is of prime importance. Many ordinary greenhouses can be adapted to make suitable homes for Alpines. No heat whatsoever is required.
Staging can be either covered with a layer of fine shingle on which to stand the pots and pans; or the staging can be boxed in to take sand or other plunging material in which the plant containers can be plunged. This saves much watering. The pots or pans should be filled with a good porous compost on top of drainage material. We use the ordinary John Innes compost which is satisfactory for the majority of plants and can be obtained, ready to use, from most reputable sundriesmen. The plants should never be over potted, the container being only slightly larger than the one in which the plant was growing when purchased. Top dress the plant with chippings after potting for cleanliness, conservation of moisture and the prevention of moss etc.
Watering should be reduced to almost nil during winter. "When in doubt don't water" is a good maxim. If it is felt to be absolutely necessary, soak the pot from below in two inches of water for ten minutes. As soon as growth starts in the spring, the watering should be increased and from now on, during the growing season, the plant should never be allowed to dry out. Light shading in the form of Cool Glass (Made by Bio) will be required during the summer. Here all plants, as they finish flowering, are plunged outside in suitable plunging materials. At all times, give as much ventilation as possible. A visit to the Alpine House at the RHS Gardens, Wisley, would be rewarding.
Dry stone walls
Many plants succeed and look their best when planted sideways in dry walls. It must be remembered that no plant will grow without ample soil in which to root. It is therefore useless (except in one or two cases) to attempt to plant a freestanding dry wall in which there is no soil. Even if soil is added in the form of pockets, success will be very limited. The proper kind of wall in which to plant is a retaining wall, i.e. a wall that is holding up a bank of soil. When planting make sure that there is no gap between the roots of the plant and the soil being held up by the wall. Any space of this sort must be rammed with soil before planting.
The wild and bog gardens
This is an area usually consisting of a track wandering through very informal beds among sparsely planted trees and shrubs which give shade and cool conditions where needed. It is devoted to plants that would look out of place in a formal border, such as Meconopsis, Primulas, many Irises, Euphorbias, Thalictrums etc. The soil should be well dug and heavily dressed with compost, leaf mould or very old manure. If there is natural moisture in the form of a stream, spring or ditch, this can easily be made into a bog garden. Where there is no water it can be introduced by one of the little electric pumps on the market. Only a small trickle is required to keep the soil sufficiently moist to grow Primulas and Calthas etc. to perfection.
Use of rocks
a) They should look as natural as possible
b) They should be as large as possible, but still in proportion with the rest of the garden.
c) Stone natural to the district is often best and certainly the cheapest.
Types of rock used
Westmorland Stone weathered limestones of Westmorland, grey in colour showing natural strata.
Limestone the weather worn limestone from Somerset, Cumberland and Derbyshire is very attractive and is often used. In the limestone, pockets of organic matter are often found which are suitable for ericaceous plants. Check for free lime content if considering planting an acid feature.
Cheddar Limestone weather worn limestone from Cheddar in Somerset. The natural rocks provide a good foil for Alpine plants. At Cheddar, plants such as the Cheddar Pink can be seen growing naturally.
Tufa the material deposited by calcareous springs, usually white or yellow, sometimes soft in texture as seen in the Cheddar caves of Somerset and sometimes hard enough to use to form a building stone as seen in the crypt of Rochester Cathedral. Plants usually grow in the soft form. Source of supply C. Field, Glasfrym, Bodfari, Denbeigh, North Wales.
Granite an igneous rock composed of crystals of quartz, felspar and mica of coarse grain. It results from the slow cooling of a large molten mass. It is an example of a harder stone, used in rock garden construction in Wales, Devon and Cornwall. The hard stone does not absorb moisture and so does not encourage plants to cling to it.
York Stone found in Yorkshire and other areas, it is often used as kerbing stones for pavements etc. It is also found as flooring in some districts. In Yorkshire it is used in dry walls and is ideal for this purpose.
Sandstone/Millstone such as is found in Sussex and the Cotswolds are very suited to plant growth but do not weather well and are often angular in shape and difficult to use.
Building a rock garden
To plan, build and plant a rock garden successfully a number of simple, but important basic principles must be observed.
Choice of Site
It is not always easy to select the perfect situation and the right conditions may have to be created artificially. The three main requirements are :
1. An open site away from large trees and hedges but protected from easterly winds.
2. A really good fall on the site from end to end.
3. Good drainage.
Before construction starts it is advisable to consider the aims of the exercise. Nature produces as an example to us, thousands of beautiful rock gardens which can be seen all over Derbyshire and other rocky districts. To build a rock garden is to construct one of these natural gardens in miniature to provide a perfect foil and ideal conditions for Alpine plants.
Canon Ellacombe sums this up well in the following quotation: "Avoid everything that suggests artifice and even suggests Man's labour. Of course there must be artifice and there must be human labour But they should be kept out of sight as much as possible."
In natural conditions the best-weathered outcrops seem to grow into their bold sentinel positions leaving huge areas of stone buried beneath, so start with the biggest piece of rock and build up to the highest elevation. Choose for the top, the more rounded stones for these give the correct appearance of gradual weathering. The more angular harder stones will go into the lower part and especially near water where they would have persisted in this form.
Anything normally spread out horizontally out to form layers is the definition of strata. The term is used to denote the layers which constitute many rocks and soils which can be seen in section at quarries etc. They arise from the manner in which the materials of rock etc. have been deposited through the ages. The arrangement of these layers in a natural fashion in building rock gardens is important and should be carefully studied. The strata it will be found, are usually inclined and often undulated. Not all rocks show them. Those like granite which have been exposed to such great heat that they have been melted are not stratified.
Only plant if conditions are suitable never when the soil is frozen or waterlogged. "Plant as you go" is a very good principle, less damage will be done to roots and crowns if this is followed, but it does require careful forethought. Build deep pockets containing soil mixtures suitable for the plants. Plant at the correct depth and in irregular groups of three or five of a species. A wide variety of Alpines need differing conditions and these can be varied in the soil mixtures. Cover as large an area of the plant roots as possible with rock to provide natural conditions. Finally, remember that Alpines like space, light and air so give them room to breathe and spread.
Calendar of work in the rock garden
March - Remove debris (frost protection), leaves etc. Remove dead growths leaving the bud protected. Topdress with suitable mixture if required.
April / May - Firm any loose soil and plants, fill any gaps with new plants. Use group plantings. Weed if required. Consider watering.
June / September - Weed carefully, water carefully. Watch out for pests and diseases. Collect seed e.g. Primula vialii.
October - Provide winter protection e.g. glass for Primula whitei etc., pine needles for Cyclamen coum etc.
Note - Topdressing can be made to suit the particular needs of the plant,e.g. granite chips, leaf mould, shredded turves 1:1:1 or leaf mould and forest bark 1:1.
Pests and diseases
Mice eat bulbs, especially Crocus and Cyclamen. Damage is done underground and is often unobserved until too late.
Birds can be a problem to many plants of cushion habit. Use wreath wires to protect the plants.
Slugs & Snails may eat whole rare Alpines overnight e.g. Campanulas. Use slug pellets or granules or other biological methods.
Aphids such as greenfly, whitefly etc. may also attack roots e.g. Primulas. Use insecticide as directed, repeat as required.
Caterpillars can devour foliage. Remove by hand or spray with a suitable insecticide.
Earwigs these can be a problem in the Alpine house. Control with suitable insecticide.
Red Spider Mite are difficult to eradicate but use of insecticides will help.
Ants can be a problem to both plant and gardener. There are many good chemical controls available. Make certain that ants are not attracted by honeydew created by infestations of aphids.
Vine Weevil – Armillatox can be used to deter egg laying and suffocate larvae, Provado maybe used in pots and containers but must never be used in the open ground due to persistence of the material in the ground.
There are many ways to increase your stock of Alpines, besides paying a visit to the local garden centre!
Purchasing seed (can be costly) to be sown green in summer of March to April.
Collecting seed (fun and cheap) e.g. Primulas etc.
Softwood cuttings taken in early summer and overwintered in cold frame.
By division in autumn or spring.
Layering of Rhododendrons etc.
Grafting Daphne petrea, Pinus pumila etc.
There are numerous books on the subject of Alpines and the list given below is only a small selection of those available from book shops, garden centres and your local library.
Manual of Alpine Plants by W. Ingwerson
Propagation of Alpines by Lawrence Hills
Rock Gardens by W. Schacht
Gentians by Mary Bartlett
Collectors Alpines by Royton E. Heath
The Dry Garden by Beth Chatto
Collins Guide to Alpines by Anna N. Griffiths
Miniature Shrubs by Royton E. Heath
Dwarf Bulbs by B. Mathew
Alpine Flowers of Europe by Wilson/Blamey
Sources of supply
Mail order unless otherwise stated. We recommend that you telephone to check opening times etc. before visiting any of these nurseries.
Paul Christian, PO Box 468, Wrexham, Clwyd LL13 9XR. Tel: 01978 366399. Mail order only.
Holden Clough Nursery, Holden, Bolton by Bowland, Clitheroe, Lancs.BB7 4PF. Tel:012007 615.
Glendoick Gardens Ltd., Glencarse, Perth, Scotland. PH2 7NS. Tel: 0173 886735.
Edrom Nurseries, Coldingham, Eyemouth, Berwickshire, Scotland. TD14 5TZ. Tel: 018907 71386
Potterton Nursery, The Cottage Nursery, Moortown Road, Nettleton, Nr Caistor, Lincs. LN7 6HX. Tel: 01472 851792
Hartside Nursery Garden, Low Gill House, Alston, Cumbria, CA9 3BL. Tel: 01434 381372.
Alpine Garden Society, Avon Bank, Pershore, Worcestershire WR10 3JP.
Scottish Rock Garden Club, Richard Green, Cedar Cottage, Balfron Station, Glasgow G63 0SQ. Telephone: +44 (0)1360 440701
Plants for the rock garden
AETHIONEMA ARMENUM summer flowering, pink 4 inches high.
Silvery saxifrages e.g. SAXIFRAGA BURSERANA summer flowering, white, rose and yellow, 4 inches high.
Encrusted Saxifrages - SAXIFRAGA AIZOON summer flowering, white, rose, yellow & purple 4 6 inches high.
PHLOX SUBULATA April May flowering, rose purple, 6 inches high.
DIANTHUS GRATIANOPOLITANUS May July flowering, pink red up to 12 inches high.
DIANTHUS NEGLECTUS July August flowering, rose red up to 6 inches high.
CAMPANULA COCHLEARIFOLIA June August, blue, 4 6 inches high.
DRYAS OCTOPETALA June flowering, white, 4 6 inches high.
SAPONARIA OCYMOIDES June flowering, rose, 4 6 inches high.
ONOSMA ECHIOIDES flowering June onwards, pale yellow 6 12 inches tall.
MORISIA MONANTHOS March to May flowering, golden yellow 6 12 inches high.
ANDROSACE SARMENTOSA May June flowering, rose with silvery foliage 3 4 inches high.
ANDROSACE LANUGINOSA flowers June-October, pink, silvery foliage, 3 4 ins high.
SAXIFRAGA LONGIFOLIA June flowering, white 8 24 inches high.
LEWISIA spp. Spring flowering, white, pink & red. 2 9 inches high.
HYPERICUM REPTANS autumn flowering, yellow, 1 inch high.
DRYAS OCTOPETALA June flowering, white, 3 inches high.
MAZUS REPTANS Flowers in summer,purplish/blue, 1 2 inches high.
MOSSY SAXIFRAGES flowering in spring 3 9inches high.
ACAENA MICROPHYLLA Crimson flowers in summer 1 2 inches high.
ARENARIA BALEARICA Flowers March August 3 inches high.
VERONICA REPENS September flowering, whitish, 4 inches high.
CROCUS VERNUS February April, white purple.
CROCUS SPECIOSUS Sept. October, lilac.
NARCISSUS BULBOCODIUM February May, yellow or white, 4 8 inches tall.
NARCISSUS CYCLAMINEUS February flowering, lemon coloured inches high.
NARCISSUS POETICUS April, white with red centres, 12 inches tall.
CAMASSIA QUAMASH White blue 2 3 eet tall.
GLADIOLUS BYZANTINUS June flowering, red colour 2 ft. high.
LILIUM MARTAGON June July, purplish red, 2 4ft. high.
LILIUM MARTAGON ALBUM June July, white 2 4 ft. high.
TULIPA SYLVESTRIS April flowering, yellow and red 12 inches high.
PULSATILLA VULGARIS April flowering, mauve or white, 8 inches high.
GERANIUM PRATENSE June September, blue, 3 4ft. tall.
SAXIFRAGA GRANULATA White, 12 inches high.
THYMUS SERPHYLLUM purplish in colour flowers 1 3 inches high.
HELIANTHEMUM NUMMULARIUM hybrids June July flowering, various colours, 1ft. high.
Scree & Moraine
GENTIANA VERNA May June, deep azure, 4 inches high.
PAPAVER ALPINUM summer flowering white or yellow, 10 inches tall.
POTENTILLA NITIDA July August flowering, pink, 4 inches high.
LEONTOPODIUM ALPINUM June July, enveloped woolly bracts, 6 inches high.
CARLINA ACANTHIFOLIA June flowering, white, 2 ft. tall.
DAPHNE PETRAEA Flowering in May June, rose, 3 6 inches.
DRABA BRUNIIFOLIA March flowering, yellow, 4 inches high.
OMPHALODES LUCILIAE Summer flowering, rose, blue, 3 6 inches high.
RAOULIA AUSTRALIS Mat forming yellow plant.
ASPERULA SUBEROSA June July, pink 3 inches.
LUPINUS ORNATUS May October, pinkish flowers, 18 30 inches tall
DIANTHUS ALPINUS June August, pink/red, 4 inches high.
PENSTEMON MENZIESII June, violet blue 1 foot tall.
OXALIS ADENOPHYLLA May July flowering, lilac pink 4 6inches high.
RHODOHYPOXIS BAURII June Sept. rose red flowers, 4 inches high.
Moist Lower End of Moraine
GENTIANA FARRERI August flowering, blue, 8 inches high.
NIEREMBERGIA REPENS July, white & yellow, 2 3 inches tall.
SAXIFRAGA OPPOSITIFOLIA early spring, purple, pink & red. 1 2 inches high.
Hot & Dry Situations
SEDUM varieties June/July, various colours 1 6 inches tall.
SEMPERVIVUM varieties June, various colours, 2 12 inches high.
MESEMBRYANTHEMUM varieties June July, red, pink, white, yellow, mauve, 2 3 ins high.
Wall plants for a sunny aspect
CAMPANULA PORTENSCHLAGIANA June/July, light blue 6 9 inches high.
CAMPANULA COCHLEARIFOLIA June August, blue flowers, 4 6 inches.
AUBRETIA DELTOIDEA April/May flowering, lilac red/purple 6 9 inches high.
ALYSSUM SAXATILE April June, yellow flowers, 12 inches high.
DIANTHUS GRATIANOPOLITANUS _ May to July floweing, pink red in colour 1ft.tall.
HELIANTHEMUM garden hybrids June, various colours, 3 9 inches.
PHLOX SUBULATA hybrids April May, rose purple, 6 inches high.
ARABIS ALBIDA January to May flowering, white, 6 9 inches.
IBERIS SEMPERVIRENS spring & summer flowering, white, 9 12 inches.
SAXIFRAGA UMBROSA early summer, pink flowers, 12 18 inches high.
SAXIFRAGA DECIPIENS & all mossy saxifrages spring, white pink & red, 3 9inches high.
HUTCHINISIA ALPINA May July, white flowers, 1 3 inches high.
MAZUS REPTANS summer flowering, purplish blue flowers, 1 2 inches tall.
GENTIANA ASCLEPIADEA July August, azure blue flowers, 6 24 inches tall.
AQUILEGIA GLANDULOSA var.JUCUNDA May June, blue & white flowers, 8 12 in high.
MECONOPSIS CAMBRICA June August, yellow, orange blooms, 9 15 inches high.
LEIOPHYLLUM BUXIFOLIUM May flowering, white/pink, 12 15 inches.
HOUSTONIA CAERULEA June onwards, light blue/white, 3 6 inches tall.
North Facing Joints
SAXIFRAGA OPPOSITIFOLIA early spring, puple, pink or red flowers, 1 3 inches high.
RAMONDA MYCONI May June, purple flowers, 4 8 inches high.
PRIMULA EDGEWORTHII April flowering, pale mauve white-eye, 4 8 inches high.
ARENARIA BALEARICA March to August, white flowers, 3 inches tall.
PRIMULA ROSEA early spring, purple, pink or red flowers, 1 3 inches high.
DODECATHEON MEADIA May June, rose coloured flowers, 9 24 inches tall.
TROLLIUS EUROPAEUS June August, yellow flowers, 1 2 feet high.
PRIMULA JAPONICA May June, purplish red, 18 inches high.
PRIMULA PULVERULENTA June flowering, deep red, up to 3ft. tall.
Abies procera glauca prostrata
Chamaecyparis obtusa nana gracilis
Chamaecyparis obtusa nana lutea
Juniperus horizontalis Blue Chip
Juniperus communis compressa
Juniperus procumbens nana
Picea glauca Albertiana conica
Taxus baccata standishii
The information given in this Fact Sheet is provided in good faith. It is however of necessity general information and advice on the topic. Howard Drury will not be under any liability in respect of the provision of such advice and information and you are strongly advised to seek independent advice on any particular gardening problems or queries you may have, preferably from experts who can (when appropriate) inspect the problem before providing advice.
(C) 2020. This material has been produced by Howard Drury and must not be reproduced in part or full without the written consent of Howard Drury, Kings Heath Birmingham B13 0SJ.