Cool conservatory and greenhouse plants

There is a big choice of plants from diverse habitats for gardeners with cool but frost-free conservatories and greenhouses.

Introduction

There is a big choice of plants from diverse habitats for gardeners with cool but frost-free conservatories and greenhouses. Plants such as citrus, cool growing orchids and cacti, provide opportunity to establish collections of one group or, if preferred, an interesting mix of forms and flowers from those listed here.

Practical considerations

The general requirement for cool growing conservatory or greenhouse plants is the provision of a minimum night-time temperature of 5°C (41°F) through the winter months, as they are not frost hardy.

Suitable plants

For heated structures see our page on plants for warm conservatories and greenhouses.

Key
AGM
= Denotes plants which have received the Society's Award of Garden Merit
(f) = Denotes plants with fragrant flowers or foliage

Climbers

Aristolochia macrophylla: mottled, mid-green flowers in summer. Height and spread 8m (25ft) by 10m (33ft)
Bomarea caladsii AGM: spotted red to orange flowers from spring to autumn. Height to 4m (13ft)
Bougainvillea: bracts in all colours except blues in summer and autumn. Height and spread 12m (40ft) by 8m (26ft)
Cobaea scandens AGM: flowers cream to purple in summer and autumn. Height to 20m (66ft)
Distictis buccinatoria: purple-red flowers in summer and autumn. Height to 25m (82ft)
Eccremocarpus scaber: orange-red flowers in spring to autumn. Height to 5m (16ft)
Hoya carnosa AGM: (f) white flowers with red coronas in spring to autumn. Height to 6m (19ft)
Jasminum mesnyi AGM: yellow flowers in spring and summer. Height and spread to 3m (10ft) by 2m (6½ft)
J. polyanthum AGM: (f) white flowers in late winter to spring. Height to 6m (19ft)
Kadsura japonica: yellowish white flowers in summer and autumn. Height 4m (13ft)
Kennedia nigricans: purple black flowers in late winter to early summer. Height to 6m (19ft)
K. rubicunda: dark red flowers in spring and summer. Height to 3m (10ft)
Lapageria rosea AGM: pink to red flowers in summer to autumn. Height 5m (16ft)
Mandevilla laxa AGM: (f) white flowers in summer and autumn. Height to 5m (16ft)
Mutisia decurrens: orange flowers in summer. Height 3m (10ft)
Pandorea jasminoides AGM: red-throated white flowers in spring and summer. Height 5m (16ft)
P. pandorana: purple-spotted yellow flowers in winter and spring. Height 6m (19ft)
Passiflora ‘Amethyst’ AGM: purple flowers in summer and autumn
P. caerulea AGM: white and blue flowers in summer to autumn. Height 10m (33ft)
P. × exoniensis AGM: pink and white flowers in summer. Height 6m (19ft)
P. mollissima AGM: oink flowers in summer to autumn. Height 5m (16ft)
P. × violacea AGM: red-purple flowers in summer and autumn. Height 6m (19ft)
Plumbago auriculata AGM: sky-blue flowers in summer to autumn. Height and spread to 6m (19ft) by 3m (10ft)
Solanum laxum ‘Album’ AGM: white flowers in summer to autumn. Height 6m (19ft)
Sollya heterophylla AGM: blue flowers in summer to autumn. Height to 2m (6½ft)
Thunbergia alata: chocolate-centred orange flowers in summer to autumn. Height to 2m (6½ft)
Tropaeolum tuberosum: yellow to orange flowers from summer to autumn. Height: to 4m (13ft)
Tweedia caerulea AGM: turquoise blue flowers in summer to autumn. Height 1m (3¼ft)

Shrubs

Abutilon: flowers in all colours including blue, from spring to autumn. Height and spread to 3m (10ft) by 2m (6½ft)
Acacia dealbata AGM: (f) yellow flowers in winter to spring. Height and spread to 30m (100ft) by 10m (33ft)
A. pravissima (f) yellow flowers from winter to spring. Height and spread to 8m (26ft) by 7m (23ft)
Agave: grown for ornamental foliage forming rosettes. Height and spread variable according to species
Aloysia citrodora AGM: (f) grown for lemon-scented foliage. Height and spread both to 3m (10ft)
Banksia: flowers range from cream to orange red. Height and spread to 10m (33ft) by 8m (26ft) although some species are smaller.
Caesalpinia gilliesii: yellow flowers in summer. Height and spread to 3m (10ft) by 2.5m (8ft)
Callistemon citrinus 'Splendens' AGM: red flowers in spring and summer. Height and spread both to 8m (26ft)
C. rigidus: deep red flowers in summer. Height and spread to 2.5m (8ft) by 3m (10ft)
Camellia (need lime-free soil):  flowers from white through to red, rarely yellow, from winter to spring. Height and spread to 9m (30ft) by 8m (26ft)
Cestrum aurantiacum: orange flowers in spring to early summer. Height and spread to 3m (10ft) by 2m (6½ft)
Chamaerops humilis AGM: dwarf palm, grown for foliage. Height and spread to 3m (10ft) by 2m (6½ft)
Citrus: (f) white flowers generally in spring and summer. Height and spread to 12m (40ft) by 5m (16ft)
Clianthus puniceus AGM: red flowers in spring and summer. Height and spread 4m (13ft) by 3m (10ft)
Coprosma: produce ornamental white to orange berries. Height and spread to 8m (25ft) by 3m (10ft)
Cordyline australis AGM: (f) Grown for foliage. Height and spread to 10m (30ft) by 4m (13ft)
Coronilla valentina subsp. glauca AGM: (f) yellow flowers from winter to spring. Height and spread both 80cm (32in)
Correa: cream to red flowers from autumn to spring. Height and spread both to 3m (10ft)
Cyathea: genus of tree ferns. Height and spread: to 15m (49ft) by 6m (19ft)
Daphne mezereum: (f) purplish-pink flowers in late winter and spring. Height and spread 1.2m (4ft) by 1m (3¼ft)
Dicksonia antarctica AGM: Genus of tree ferns. Height and spread to 6m (20ft) by 4m (13ft)
Dodonaea viscosa: grown for evergreen foliage. Height and spread to 5m (16ft) by 3m (10ft)
Erica canaliculata AGM: pale, pinkish-white flowers in late winter to spring. Height and spread 2m (6½ft) by 1.2m (4ft)
E. gracilis: pink to cerise flowers from autumn to spring. Height and spread both 50cm (20in)
E. pageana: yellow flowers in late winter to early spring. Height and spread 60cm (2ft) by 30cm (1ft)
Eucalyptus citriodora: (f) grown for its lemon scented foliage. Height and spread to 50m (165ft) by 20m (66ft)
Eupatorium ligustrinum AGM: cream to pink flowers in autumn. Height and spread both to 5m (16ft)
Fuchsia procumbens: green, purple and orange flowers in summer. Height and spread to 15cm (6in) by 1.2m (4ft)
Genista canariensis AGM: yellow flowers in spring and summer. Height and spread to 2m (6½ft) by 1.2m (4ft)
Lantana camara: flowers in shades from white, yellow to red. Height and spread both 2m (6½ft)
Leptospermum scoparium: pinkish- white flowers in spring and summer. Height and spread both 3m (10ft)
Lotus berthelotii : black-centred scarlet flowers in spring and summer. Height and spread 20cm (8in) by indefinite.
Mimulus aurantiacus AGM: yellow to scarlet flowers from summer to autumn. Height and spread both 1m (3¼ft)
Myrtus communis AGM: white flowers in summer. Height and spread both 3m (10ft)
Nerium oleander: (f) pink red or white flowers in summer. Height and spread 6m (19ft) by 3m (10ft)
Phoenix canariensis AGM: palm, grown for foliage. Height and spread to 15m (50ft) by 12m (40ft)
Pittosporum eugeniodes: greenish-yellow flowers in summer. Height and spread 12m 40ft) by 5m (16ft)
P. eugenioides ‘Variegatum’ AGM: f) as above, but with bold cream margins to the leaves
P. tobira AGM: (f) white flowers in spring and summer. Height and spread 10m (33ft) by 3m (10ft)
P. tobira ‘Variegatum’ AGM: as above, but leaves are greyish green margined with white.
Protea cynaroides: flower heads with red, pink or cream bracts in spring and summer. Height and spread both 2m (6½ft)
Punica granatum: orange-red flowers in summer. Height and spread 6m (20ft) by 5m (16ft)
Rhododendron ‘Fragrantissimum’ AGM: white flowers in spring. Height and spread both 2m (6½ft)
Solanum laciniatum: blue flowers in summer and autumn. Height and spread 2m (6½ft) by 1.5m (5ft)
Sutherlandia frutescens: red flowers in spring and summer. Height and spread 2m (6½ft) by 1.5m (5ft)
Telopea specioissima: red flowers in spring. Height and spread 3m (10ft) by 2m (6½ft)
Tibouchina urvilleana AGM: purple flowers in summer and autumn. Height and spread 6m (19ft) by 3m (10ft)
Trachycarpus fortunei AGM: palm, grown for its foliage. Height and spread to 20m (66ft) by 2.4m (8ft)
Yucca aloifolia: white flowers from summer to autumn. Height and spread 8m (26ft) by 5m (16ft)


Bulbous, rhizomatous and herbaceous plants

Agapanthus: blue flowers in late summer. Height and spread 90cm (3ft) by 45cm (1½ft)
Alstroemeria aurea: orange with red streaks in summer. Height and spread 90cm (3ft) by 45cm (1½ft)
Amaryllis belladonna AGM: (f) pink flowers in autumn. Height and spread 60cm (2ft) by 10cm (4in)
Anigozanthos flavidus: greenish yellow flowers in late spring and summer. Height and spread: to 3m (10ft) by 90cm (3ft)
A. manglesii AGM: red and dark green flowers in spring and summer. Height and spread to 1.2m (4ft) by 60cm (2ft)
Argyranthemum frutescens subsp. canariae: yellow flowers in summer and autumn. Height and spread both 70cm (28in)
A. foeniculaceum: white flowers in summer and autumn. Height and spread both 80cm (32in)
Arthropodium cirratum: purple and yellow spotted flowers in summer. Height and spread 90cm (3ft) by 30cm (1ft)
Aspidistra elatior AGM: green foliage plant. Height and spread both 60cm (2ft)
Babiana stricta AGM: (f) mauve or yellow flowers in spring. Height and spread 30cm (1ft) by 5cm (2in)
Begonia grandis subsp. evansiana AGM: pink or white flowers in summer. Height and spread 50cm (20in) by 30cm (1ft)
Billbergia nutans: green flowers with navy-blue margins from a pink bract. Height and spread 50cm (20in) by indefinite
Bletilla striata AGM: magenta flowers from spring to early summer. Height and spread 30cm (1ft) by 60cm (2ft)
Calceolaria integrifolia AGM: yellow flowers over summer. Height and spread to 1.2m (4ft) by 30cm (1ft)
Campanula isophylla AGM: pale blue to white flower in midsummer. Height and spread 20cm (8in) by 30cm (1ft)
Canna iridiflora: cerise flowers from midsummer to autumn. Height and spread 3m (10ft) by 50cm (20in)
Clivia miniata AGM: orange red to yellow flowers in spring and summer. Height and spread 45cm (18in) by 30cm (1ft)
Crinum × powellii: (f) pink flowers from late summer to autumn. Height and spread 1.5m (5ft) by 30cm (1ft)
C. moorei: (f) pink flowers produced in autumn. Height and spread 90cm (3ft) by 30cm (1ft)
Cyrtanthus elatus AGM: scarlet flowers in late summer. Height and spread to 60cm (2ft) by 10cm (4in)
Freesia lactea: (f) white flowers in spring. Height to 40cm (16in) 
Gazania cultivars: flowers in red orange and yellow with central markings. Height and spread both to 25cm (10in)
Geranium maderense AGM: pink flowers in early spring to late summer. Height and spread both to 1.5m (5ft)
Gerbera: flowers in all colours except blue from late spring to late summer. Height and spread to 45cm (18in) by 60cm (2ft)
Hedychium 'Tara' AGM: red or orange flowers in late summer to autumn. Height and spread 3m (10ft) by 1m (3¼ft)
H. coronarium: (f) white flowers with yellow centres in mid to late summer. Height and spread
H. gardnerianum AGM: (f) 3m (10ft) by 1m (3¼ft)
H. greenii: orange red flowers in summer. Height and spread 2m (6½ft) by 60cm (2ft)
Hesperantha coccinea: scarlet flowers in autumn (Height and spread to 60cm (2ft) by 30cm (1ft)
Lachenalia aloifolia: scarlet –tipped yellow flowers in winter or early spring. Height and spread to 28cm (11in) by 5cm (2in)
Moraea polystachya: violet-blue flowers with yellow centres in summer. Height and spread to 80cm (32in) by 8cm (3in)
Nerine bowdenii AGM: pink flowers in autumn. Height and spread 45cm (18in) by 8cm (3in)
N. sarniensis: crimson to orange red flowers in early autumn. Height and spread 45cm (18in) by 8cm (3in)
Pelargonium citronellum: (f) pinkish-purple flowers from spring to summer. Height and spread both to 2m (6½ft)
Salvia confertiflora: orange-red flowers in late summer to autumn. Height and spread to 1.2m (4ft) by 60cm (24in)
S. fulgens AGM: red flowers in summer. Height and spread 1m (3¼ft) by 90cm (3ft)
Sandersonia aurantiaca: orange flowers in summer. Height and spread 75cm (30in) by 10cm (4in)
Schizanthus pinnatus: spotted flowers in white, red, pink or purple with yellow throats from spring to autumn. Height and spread to 50cm (20cm) by 30cm (1ft)
Soleirolia soleirolii: grown as foliage plant. Height and spread 5cm (2in) by indefinite (note: can have invasive properties if planted in the garden)
Sparaxis tricolor: orange red or purple flowers from spring to summer. Height and spread to 40cm (16in) by 8cm (3¼in)
Strelitzia reginae AGM: red and purple flowers from winter to spring. Height and spread to 2m (6½ft) by 1m (3¼ft) 
Veltheimia capensis AGM: white or pink spotted flowers in spring. Height and spread 45cm (18in) by 30cm (1ft)
V. bracteata AGM: yellow-spotted, pinkish-purple flowers in spring. Height and spread 45cm (18in) by 30cm (1ft)
Watsonia pillansii: orange to orange-red flowers from summer to autumn. Height and spread to 1.2m (4ft) by 10cm (4in)
Zantedeschia aethiopica: white flowers from spring to midsummer. Height and spread both 90cm (3ft)
Zephyranthes grandiflora: pink flowers from summer to early autumn. Height and spread to 30cm (1ft) by 5cm (2in)


Aquatic Plants

Nelumbo nucifera: pink or white flowers in summer. Height and spread height to 1.5m (5ft) by indefinite
Thalia dealbata: violet-blue flowers in summer. Height and spread to 3m (10ft) by 2m (6½ft)

<EM>Geranium maderense</EM>
<EM>Nelumbo nucifera</EM>
<EM>Strelitzia reginae</EM>
    Geranium maderense Nelumbo nucifera Strelitzia reginae

    References

    A useful reference for conservatory gardening is Indoor Conservatory and Greenhouse Gardening by Ann Bonar, Alan Toogood, Deenagh Goold-Adams and Ray Waite. RHS/Cassell 1994 ISBN 0 304 32075 7

    Conservatory and Indoor Plants Volume 1 (ISBN0 333 67737 4) and Volume 2 (ISBN 0333 67738 2) by Roger Phillips and Martyn Rix. Macmillan 1997, provides a wealth of colour photographs and descriptions.

    These books are made available through the RHS Lindley Library online catalogue.

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