Chalky soils: plants for

Chalky soils are alkaline and free-draining, and the depth of soil over chalk varies considerably. The key to gardening in these often drought-prone and nutrient poor soils is to select from the wide range of colourful plants that thrive in dry summers, need sharp drainage and moderate to low fertility.

Limestone soils have similar characteristics.

 

Chalky soils: plants for

Quick facts

Top 5 plants for chalk:
Ceanothus
Campanula
Clematis
Dianthus
Geranium
Lavandula

Introduction

Many chalky soils are shallow, very free-draining and low in fertility, but variations exist. Where there is clay present, nutrient levels may be higher and the water holding capacity greater.

Where chalky soils are deep, they can be moisture-retentive and support a wide range of plants. They will not support ericaceous plants such as camellia and rhododendrons that need acid soil conditions. Very chalky soils may contain lumps of visible chalky white stone. Such soils cannot be acidified, and it is better to choose plants that will thrive in alkaline conditions.

When planting on chalky soils it is important to first establish how deep the topsoil is. Many trees and shrubs that will tolerate alkaline soil conditions may become chlorotic (yellow) on shallow soils over chalks. In some gardens the soil layer may be very thin indeed – only a few inches – before hitting solid chalk. Where this is the case, topsoil will need to be brought in to make planting possible. On shallow soils over chalk where increasing soil depth is not an option, wildflower mixes selected for chalk tolerance may still thrive.

Practical considerations

When planting on chalky soils;

  • Break up the chalk to a depth of 75cm (30in) so that plant roots can spread out and establish
  • Whether bringing in new soil or improving existing soil, add plenty of well-rotted organic matter such as garden compost, composted green waste or farmyard manure
  • Smaller plants get established more quickly than more mature specimens
  • Mulch plants with organic matter to conserve moisture
  • Attention to watering will be required for a longer period than with other soil types as plants on chalky soils may take several seasons to establish and are more prone to drying

    Suitable plants

    (+)   Best grown on deep and moisture retentive soils over chalk
    (gc) Ground cover plants
    (v)   variegated foliage
    (e)   evergreen foliage
    AGM - The RHS Award of Garden Merit

    Many popular species and cultivars are listed below If you would prefer to view a full list of suitable plants for chalky and alkaline soils, try the RHS Find a Plant.

    Trees

    Acer campestre, A. negundo, A. platanoides, A. pseudoplatanus
    Aesculus × carnea, A. hippocastanum
    (horse chestnut), A. indica
    Arbutus unedo
    (+) (e)
    Carpinus betulus (common hornbeam)
    Ceanothus arboreus 'Trewithen Blue' AGM (e)
    Cercis siliquastrum
    Corylus avellana cultivars, C. avellana 'Contorta' AGM, C. colurna AGM, C. maxima cultivars
    Crataegus laevigata (hawthorn)
    Euonymus europaeus (spindle)
    Fagus sylvatica (common beech)
    Fraxinus excelsior, F. ornus (ash)
    Ligustrum lucidum AGM (e)
    Malus (apple, crab apple)
    Morus nigra (black mulberry)
    Prunus
    (flowering cherries)
    Pyrus (common pear and ornamental) (+)
    Quercus robur (common oak)
    Sorbus aria (whitebeam), S. intermedia

    Conifers

    Cedrus including C. atlantica (Atlas cedar), C. deodara AGM (Deodar cedar), C. libani AGM (Cedar of Lebanon) (e)
    Chamaecyparis (+) (e)
    Ginkgo biloba (+)
    Juniperus communis and J. × pfitzeriana (e)
    Larix decidua, L. kaempferi (+)
    Pinus mugo and P. nigra (e)
    Taxus baccata (yew) (e) 
    Thuja occidentalis (White cedar) , T. plicata (Western red cedar) (e)
    Thujopsis dolobrata (e)

    Shrubs

    Aucuba japonica (e)
    Berberis
    Brachyglottis Dunedin Group 'Drysdale', B. Dunedin Group 'Sunshine' AGM, B. monroi,
    B
    Walberton's Silver Dormouse = 'Walbrach' AGM (e)
    Buddleja davidii cultivars, B. fallowiana var. alba AGM, B. globosa AGM, B. lindleyana, B. × weyeriana
    Buxus microphylla, B. sempervirens 'Latifolia Maculata' AGM (v), B. sempervirens 'Suffruticosa' (e)
    Caragana arborescens
    Ceanothus including C. 'Autumnal Blue' AGM, C. 'Dark Star' AGM, C. 'Concha' AGM,
    C.
    'Pershore Zanzibar' (v), C. 'Puget Blue' AGM, C. thrysiflorus var. repens AGM (e)
    Ceratostigma including C. willmottianum Forest Blue = 'Lice' AGM, C. plumbagnoides (gc)
    Cistus including C. × argenteus 'Peggy Sammons', C. creticus, C. × dansereaui 'Decumbens' AGM,
    C. laurifolius, C. monspeliensis, C. × pulverulentus '
    Sunset' AGM, C. × purpureus (e)
    Choisya × dewitteana 'Aztec Pearl' AGM, C. ternata AGM, C. ternata Sundance = 'Lich' AGM
    Collutea arborescens
    Cytisus
    Cornus mas
    Cotoneaster
    Deutzia
    Dipelta floribunda
    AGM, D. ventricosa
    Elaeagnus angustifolia, E. commutata, E.
    'Quicksilver'
    Euonymus fortunei cultivars (gc), E. japonicus cultivars (e)
    Forsythia 'Fiesta' (v), F. × intermedia 'Lynwood Variety' AGM, F. suspensa
    Fuchsia
    Genista cinerea, G. lydia
    × Halimiocistus sahucii
    AGM (gc), × H. wintonensis 'Merrist Wood Cream' AGM (e)
    Halimium calycinum, H. lasianthum, H. 'Susan' AGM (e)
    Hebe (e)
    Hibiscus syriacus, H. sinosyriacus
    Hypericum
    Laurus nobilis
    (+) (e)
    Lavandula (e)
    Ligustrum japoniucm, L. ovalifolium, L. quihoui (e)
    Lonicera nitida, L. pileata (e)
    Mahonia aquifolium, M. × media (+) (e)
    Olearia (e)
    Paeonia delavayi, P. suffruticosa
    Potentilla fruticosa

    Pyracantha including P. coccinea 'Red Column', P. 'Orange Glow' AGM, P. 'Teton' AGM (e)
    Rhus glabra, R. × pulvinata (Autumn Lace Group) 'Red Autumn Lace' AGM (+)
    Ribes laurifolium, R. odoratum, R. sanguineum, R.speciosum
    Romneya coulteri
    AGM
    Rosmarinus officinalis (e)
    Rubus biflorus AGM, R.cockburnianus 'Goldenvale' AGM, R. lineatus, R. spectabilis 'Olympic Double',
    R. thibetanus
    'Silver Fern'
    Sambucus nigra, S. racemosa
    Santolina chamaecyparissus, S. pinnata
    subsp.neapolitana AGM. S. rosmarinifolia (e)
    Sarcococca confusa AGM, S. hookeriana var. digyna, S. ruscifolia var. chinensis 'Dragon's Gate' AGM (e)
    Spartium junceum
    Spiraea 'Arguta' AGM, S.japonica 'Anthony Waterer' (v), S. japonica 'Goldflame',
    S. japonica
    Magic Carpet = 'Walbuma' AGM (v), S. nipponica 'Snowmound' AGM
    Syringa (lilac)
    Tamarix parviflora AGM, T. ramosissima 'Pink Cascade' AGM, T. tetrandra AGM
    Teucrium fruticans, T. × lucidrys (e)
    Viburnum (most)
    Vinca difformis, V. major, V. minor (gc) (e)
    Weigela florida, W. middendorfiana, W. praecox
    Yucca filamentosa, Y. flaccida
    (e)

    Climbers and wall shrubs

    Actinidia kolomikta AGM, A.deliciosa (Kiwi fruit)
    Akebia × pentaphylla, A. quinata, A. trifoliata
    Clematis
    Cotoneaster atropurpureus 'Variegatus' AGM, C. horizontalis
    Fremontodendron
    'California Glory' AGM (e)
    Hedera (ivy) (e)
    Jasminum beesianum, J. nudiflorum AGM, J. officinale cultivars (jasmine)
    Lonicera periclymenum (honeysuckle) (+)
    Parthenocissus henryana (Chinese Virginia creeper), P. quinquifolia (Virginia creeper),
    P. tricuspidata (Boston ivy)
    Passiflora caerulea AGM
    Solanum crispum 'Glasnevin' AGM, S. dulcamara, S. laxum 'Album' AGM
    Trachelospermum asiaticum AGM, T. jasminoides AGM (e)
    Vitis (ornamental vines)

    Herbaceous perennials

    Acanthus mollis, A. spinosus
    Achillea
    Actaea simplex
    Atropurpurea Group 'Brunette' AGM
    Adenophora bulleyana
    Agapanthus
    Agastache
    Alstroemeria
    Anchusa azurea 
    'Lodden Royalist'
    Anemone hupehensis, A. × hybrida
    Anthemis punctata
    subsp. cupaniana AGM, A. tinctoria 'E.C. 'Buxton', A. tinctoria 'Sauce Hollandaise'
    Aquilegia
    Armeria
    Artemisia absinthium 'Lambrook Silver', A. arborescens AGM, A. lactiflora Guizhou Group
    Aster  
    Astilbe
    Ballota pseudodictamnus AGM (e)
    Bergenia 'Bressingham Ruby', B. cilliata, B. 'Morgenrote' AGM, B. 'Overture' (e)
    Calendula officinalis (Pot marigold)
    Campanula glomerata 'Superba' AGM, C. 'Kent Belle' AGM, C. lactiflora 'Pritchards Variety' AGM
    Catanache caerulea 'Major' AGM
    Centaurea
    Centranthus ruber
    Cerinthe major
    'Purpurascens'
    Chelone obliqua
    Convallaria majalis
    (gc)
    Coreopsis
    Corydalis
    Crambe cordifolia
    AGM
    Crocosmia
    Cynara cardunculus AGM (cardoon), C. cardunculus  Scolymus Group (artichoke)
    Delphinium
    Dianthus (most)
    Dicentra 'Adrian Bloom', D. formosa 'Bacchanal' AGM
    Digitalis purpurea
    Doronicum 'Little Leo', D. orientale 'Magnificum'
    Echinacea pallida, E. paradoxa, E. purpurea cultivars
    Echinops bannaticus 'Blue Globe', E. ritro AGM (Globe thistle)
    Eremurus × isabellinus, E. robustus AGM cultivars (foxtail lily)
    Erigeron
    Erodium pelargoniiflorum
    Eryngium bourgatii
    'Oxford Blue' AGM, E. giganteum 'Silver Ghost' AGM, E. × oliverianum AGM,
    E. planum
    cultivars
    Eryisymum 'Bowles's Mauve' AGM (e)
    Euphorbia amygdaloides 'Craigieburn', E. characias cultivars, E. dulcis 'Chameleon', E. mellifera AGM
    Gaillardia × grandiflora 'Burgunder'
    Galega officinalis
    Gaura lindheimeri AGM
    Geranium including G. 'Ann Folkard' AGM, G. clarkei 'Kashmir White', G. endressi AGM,
    G. himalayense '
    Gravetye', G. 'Johnsons Blue', G. 'Mavis Simpson' AGM, G. nodosum,
    G. phaeum
    'Lily Lovell', G. psilostemon AGM, G. renardii AGM, G. Rozanne = 'Gerwat' AGM
    Geum rivale 'Leonards Variety', G. 'Totally Tangerine'
    Gypsophila paniculata
    Helenium
    'Bressingham Gold', H. 'Butterpat' AGM, H. 'Moerheim Beauty' AGM
    Helianthemum 'Fire Dragon' AGM, H. 'The Bride' AGM
    Helleborus argutifolius AGM, H. x ericsmithii 'Winter Moonbeam', H. × hybridus cultivars, H. niger cultivars,
    H. (Rodney Davey Marbled Group) 'Anna's Red', H. Walburton's Rosemary' = 'Walhero'
    Hemerocallis
    Hosta
    Inula hookeri, I magnifica
    Iris
    (bearded)
    Knautia macedonica
    Kniphofia
    Lamprocapnos spectabilis
    Leucanthemum × superbum
    'Aglaia', L. × superbum 'T.E. Killin' AGM, L. vulgare (ox-eye daisy)
    Liatris spicata
    Limonium platyphyllum
    Linum perenne

    Lychnis chalcedonica AGM, L. coronaria AGM
    Macleaya × kewensis 'Flamingo' AGM, M. microcarpa 'Kelway's Coral Plume' AGM
    Malva moschata, M. sylvestris
    Morina longifolia
    Nepeta × faassenii
    AGM, (cat mint), N. racemosa AGM
    Oenothera speciosa 'Siskiyou'
    Origanum 'Kent Beauty' AGM, O. 'Herrenhausen' AGM
    Paeonia 'Buckeye Belle', P. lactiflora 'Bowl of Beauty' AGM, P. 'Duchesse de Nemours' AGM
    Papaver commutatum 'Ladybird' AGM, P. nudicaule 'Summer Breeze Orange' AGM, P. orientale
    Penstemon
    Pensham series, P. 'Port Wine' AGM, P. 'Stapleford Gem' AGM, P. 'Windsor Red'
    Persicaria affinis 'Darjeeling Red' AGM, P. amplexicaulis, P. bistorta 'Superba' AGM
    Phlomis russeliana AGM, P. tuberosa 'Amazone' AGM
    Physostegia virginiana 'Summer Snow' AGM
    Platycodon grandiflorus AGM
    Polemonium caeruleum, P. carneum, P. 'Heavenly Blue'
    Potentilla atrosanguinea, P. nepalensis 'Miss Willmott', P. 'William Rollisson' AGM
    Rudbeckia fulgida var. deamii AGM, R. fulgida var. sullivantii 'Goldsturm' AGM
    Salvia guarantica 'Blue Enigma' AGM, S. 'Indigo Spires', S. nemorosa cultivars, Ssuperba cultivars,
    S. × sylvestris cultivars
    Scabiosa atropurpurea 'Chile Black', S. 'Butterfly Blue', S. caucasica 'Clive Greaves' AGM
    Sedum erythrostictum 'Frosty Morn' (v), S. 'Herbstfreude' AGM, S. 'Jose Aubergine', S. 'Matrona',
    S. spectabile cultivars, S. telephium 'Strawberries and Cream'
    Sidalcea 'Elsie Heugh' AGM, S. 'Party Girl', S. 'Rose Queen'
    Silene dioica, S. fimbriata, S. schafta 'Shell Pink', S. uniflora 'Druett's Variegated' (v)
    Solidago 'Cloth of Gold', S. rugosa 'Fireworks' AGM
    Tanacetum (pyrethrum)
    Thalictrum aquilegiifolium 'Thundercloud' AGM, T. delavayi AGM
    Tiarella cordifolia AGM, T. 'Pink Skyrocket, T. 'Spring Symphony'
    Tradescantia Andersoniana Group 'Bilberry Ice', T. Andersoniana Group 'Osprey'
    Verbascum bombyciferum, V. chiaxii 'Album', V. phoeniceum 'Violetta'
    Verbena bonariensis AGM, V. hastata, V. rigida AGM
    Veronica austriaca subsp. teucrium 'Crater Lake Blue' AGM, V. gentianoides
    Viola cornuta
    AGM, V. elatior cultivars
    Zauschneria californica 'Dublin' AGM, Z. cana 'Sir Cedric Morris'

    The vast majority of bulbs grow well in alkaline soils.
    Most lilies prefer acid soils but some tolerant of alkaline conditions are listed below:

    Lilium amabile var. luteum
    L. bolanderi
    L
    . bulbiferum, L. bulbiferum var. croceum
    L. candidum
    L. × dalhansonii
    L. davidii
    L. duchartrei
    L. hansonii
    L. henryi
    AGM
    L. × hollandicum
    L. lankogense
    L. leucanthemum
    L. longiflorum
    L. martagon
    AGM
    L. monodelphum
    L. pardalinum
    AGM
    L primulinum
    L. pulmilium AGM
    L. pyrenaicum
    L. regale AGM
    L. sulphureum

    Ornamental Grasses

    Although most grasses will thrive in well-drained sunny conditions, some particularly adaptable to dry, chalky or alkaline soils include:

    Calamagrostis × acutiflora 'Karl Foerster'
    Carex dipsacea, C. flacca 'Blue Zinger', C. oshimensis Everest = 'Fiwhite'
    Elymus magellanicus
    Eragrostis curvula
    'Totnes Burgundy', E. elliottii
    Festuca amethystina, F. glauca
    'Elija Blue', F. glauca 'Intense Blue' (e)
    Helicictotrichon sempervirens AGM
    Juncus patens 'Carman's Grey', J. patens 'Elk Blue'
    Miscanthus nepalensis, M. sinensis cultivars
    Muhlenbergia rigens
    Nassella trichotoma
    Pennisetum alopecuriodes '
    Hameln', P. 'Fairy Tails', P. orientale cultivars, P. macrourum
    Poa labillardierei
    Schizachyrium scoparium
    Sesleria caerulea
    Stipa gigantea AGM, S. tenuissima
    (e)

    Alpines

    Alchemilla conjuncta, A. erythropoda
    Androsase cylindrica, A. pubescens, A. pyrenaica
    Anemone blanda
    AGM, A. nemorosa AGM, A. pavonina
    Arabis alpina
    subsp. caucasica 'Schneehaube' AGM (e)
    Arenaria montana AGM (e)
    Armeria juniperifolia AGM
    Artemisia schmidtiana 'Nana' AGM
    Aster alpinus AGM
    Aubretia (e)
    Campanula 'Birch Hybrid' (e), C. carpatica AGM, C. cochlearifolia AGM
    Cyclamen cicilium AGM, C. coum AGM, C. hederifolium AGM
    Daphne cneorum 'Eximia' AGM, D. × hendersonii 'Ernest Hauser' (e)
    Dianthus alpinus AGM, D. anatolicus, D. 'Whatfield Cancan' AGM
    Dryas octopetala AGM
    Erinus alpinus AGM
    Erodium chrysanthum, E. manescavii
    Gentiana aculis, G. septemfida, G. verna
    Geranium
    (Cinereum Group) 'Ballerina' AGM
    Hepatica nobilis cultivars (e)
    Iberis sempervirens 'Snowflake' AGM (e)
    Incarvillea delavayi
    Iris pumila, I reticulata
    Jeffersonia diphylla, J. dubia
    Lathyrus vernus
    Lithodora diffusa
    'Heavenly Blue' AGM (e)
    Oenothera perennis
    Origanum amanum
    AGM, O. dictamnus
    Oxalis adenophylla
    AGM
    Papaver alpinum, P. nudicaule
    Phlox divaricata
    'Clouds of Perfume', P. 'Kellys Eye' AGM, P. subulata 'Purple Beauty'
    Polygala calcarea 'Lillet' AGM
    Pulsatilla vulgaris AGM
    Ranuculus
    Saponaria ocymoides AGM, S. × olivana AGM
    Saxifraga 'Southside Seedling Group', S. 'Tumbling Waters' AGM (e)
    Scutellaria suffrutescens 'Texas Rose'
    Sedum
    Sempervivum (e)
    Thymus pulegioides 'Bertram Anderson' AGM, T. serpyllum 'Pink Chintz' AGM (e)
    Veronica cinerea AGM, V. prostrata 'Spode Blue' AGM
    Viola 'Belmont Blue', V. 'Columbine', V. 'Jackanapes' AGM, V. 'Maggie Mott' AGM (e)

    Annuals 

    Antirrhinum (snapdragon)
    Alyssum
    Arctotis
    Brachyscome
    Calendula
    (pot marigold)
    Celosia
    Centaurea cyanus
    (cornflower)
    Convolvulus tricolor
    Cosmos bipinnatus, C. sulphureus
    Cynoglossum
    Echium vulgare
    (Vipers bugloss)
    Eschscholzia (California poppy)
    Felicia amelloides
    Gazania
    Godetia
    Gomphrena
    Gypsophila
    Helianthus
    (sunflower)
    Lobelia erinus
    Myosotis
    (forget me not)
    Nemesia denticulata AGM, N. 'Wisley Vanilla' AGM
    Nicotiana affinis, N. langsdorfii, N. sylvestris, N. tabacum
    Nigella damascena (love in a mist)
    Papaver commutatum
     (ladybird poppy) , P. nudicaule, P. rhoeas (Shirley poppy), P. somniferum
    Petunia
    Phacelia campanularia, P. tanacetifolia
    Salvia coccinea, S. farinacea, S. involucrata
    AGM, S. patens AGM
    Schizanthus (butterfly flower)
    Tagetes (marigold)
    Verbena
    Zinnia

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