Rock Garden Plants Fact Sheet No. 7.401 Gardening Series|Flowers by J.E. Klett and R.A. Cox* The ideal location for a rock garden is a Plant a variety of species, repeating some Quick Facts natural slope or terrace, such as those found species several times to make the garden look at the side or rear of a house based on a split- natural. Ideally, rock garden plants should • Rock gardens are effective level or garden-level design. spread slowly. Take care not to overplant. if built on a natural slope or Use rocks of one geological type. A terrace. common rock in Colorado is native granite covered with lichens (moss rock). Rocks Plant Selection • Use rocks of one geological are available from nurseries, landscape Many types of plants are suitable for type. contractors and rock dealers. An effective rock gardens. Generally, plants that are • Good drainage is necessary. rock garden should have several large rocks, low growing and have a clumping habit some weighing 200 pounds or more. are preferred. Perennial plants are most • Plant a variety of species in Set the rock into the ground so at least common in rock gardens, although some the rockery. one-third is buried. Place rocks in a natural annuals can be used. Table 1 lists many rock • The garden should not be way, following the grain of the rock. Position garden plants, along with their characteristics rocks to control soil erosion between rocks and cultural requirements. Most plants larger than can be easily and to allow soil pockets of various sizes for listed should be hardy to 8000 feet, some maintained. plants. Use smaller, similar rock as a mulch. higher. Refer to fact sheets 7.406, Flowers for Place lichen-covered rock to expose as much Mountain Communities and 7.413, Ground of the lichen as possible. Covers for Mountain Communities. Provide good drainage. Most plants Plant Select® plants may be viewed online suitable for rock gardens require a well- at www.plantselect.org. drained soil. For most plants, incorporate organic matter into heavier clay soils to improve texture and provide better drainage. Refer to fact sheets 7.222, Soil – the Key to Successful Gardening and 7.235, Choosing a Soil ­Amendment. A rock garden should be no larger than can be easily maintained. Rock gardens have high maintenance requirements. Weed control is the biggest problem. Most rock garden plants need low to moderate watering amounts and frequency. Refer to fact sheet 7.231, Xeriscape: Garden Flowers.

© Colorado State University Extension. 6/00. Revised 7/11. www.ext.colostate.edu *J.E. Klett, Colorado State University Extension horticulture specialist and professor, horticulture and landscape architecture; and R.A. Cox, Extension horticulture agent, Arapahoe County. 7/2011 Table 1: Recommended rock garden plants.

Soil Flower Bloom Plant Name Height Exposure Remarks Preference Color Period Ajuga reptans Carpet bugle 4-10 in. Shade to Well drained Blue, purple May-June Spreading ground cover. ‘Atropurpurea’ 4-6 in. part shade Well drained Violet-blue May-June Bronze-purple foliage. ‘Burgundy Glow’ 4-6 in. Shade to Well drained Blue May-June Pink, white and green foliage. ‘Chocolate Chip’ 2-4 in. part shade Well drained Blue May-June Wavy, chocolate-brown foliage. Shade to part shade Shade to part shade Alyssum montanum 4-10 in. Sun Dry, rocky Yellow April-May Gray foliage. Mountain alyssum Arabis caucasica ‘Snowcap’ 6-9 in. Sun Well drained White April-May Abundant white flowers over gray foliage. Snowcap rockcress Arctostaphylos uva-ursi Kinnikinick 6-8 in. Shade to Acid to neutral, White-tinged May-June Spreading evergreen foliage; red fruits. part sun high in humus, red well drained

‘Massachusetts’ 4-6 in. Shade to Acid to neutral, Pink-tinged April-May Spreading evergreen foliage; red fruits. part sun high in humus, well drained Armeria maritima Sea Pink 4-10 in. Sun Dry, well Pink, white, May-June Grass-like foliage; several varieties. drained purple ‘Victor Reiter’ 2-4 in. Sun Dry, well Pink April-June Small mounded plant. drained Aubrieta deltoidea Sun to part ‘Purple Gem’ 4-6 in. Well drained Purple April-June Mounded to spreading; shear after bloom. shade Purple Gem Rockcress Aurinia saxatilis 8-12 in. Sun Dry, rocky Yellow April-May Grayish-green foliage; shear after bloom. Basket-of-gold Campanula carpatica Carpathian harebell 8 in. Sun Well drained Blue-Lilac June-July Bright green foliage. ‘Blue Clips’ 6-12 in. Sun to part Well drained Blue June-July Compact mound of bright-green foliage. shade ‘White Clips’ 6-12 in. Sun to part Well drained White June-July Compact mounds of wavy, bright green shade foliage.

Campanula poscharskyana Sun to 6-8 in. Well drained Blue June-Aug. Prolific flowers. Serbian bellflower part shade

Campanula rotundifolia 8-12 in. Part shade Well drained Blue May-Sept. Bell-like flowers on slender stems. Bluebell Cerastium tomentosum Dry, well 4-10 in. Sun White May-June Aggressive; shear after bloom. Snow-in-summer drained Ceratostigma Sun to plumbaginoides 8-12 in. Well amended Blue Aug.-Sept. Foliage turns red in fall. part shade Plumbago Coreopsis auriculata Dry and well Orange- ‘Nana’ 4-8 in. Sun June-Sept. Dense compact spreading mounds. drained Yellow Dwarf Coreopsis Delosperma cooperi 2-3 in. Sun Well drained Purple June-frost Succulent foliage; to 7000’. Purple ice plant Delosperma dyeri Dry, well Succulent leaves, carpet-like Plant Select® 1-2 in. Sun Orange-red June-Sept. Red Mountain® ice plant drained 2007. Delosperma floribundum Dry, well Pink with Succulent leaves, clump form. 4-6 in. Sun June-Sept. Starburst® ice plant drained white centers Plant Select® 1998. Delosperma nubigenum Succulent foliage turns reddish-purple in 2-3 in. Sun Well drained Yellow May-June Yellow ice plant winter. Delosperma x ‘Kelaidis’ Dry, well Succulent leaves, carpet-like. ® 2-4 in. Sun Salmon pink June-Sept. ® Mesa Verde ice plant drained Plant Select 2002. Delosperma x ‘John Proffit’ Dry, well Succulent leaves, carpet-like. 2-4 in. Sun Pink-purple June-Sept. Table Mountain® ice plant drained Plant Select® 2002. (Table 1, Continued) Table 1: Recommended rock garden plants.

Soil Flower Bloom Plant Name Height Exposure Remarks Preference Color Period

Delosperma ‘Pstave’ Dry, well 2-4 in. Sun Pink-lavender June-Sept. Succulent leaves, Plant Select® 2009. Lavender Ice™ ice plant drained

Dianthus deltoides Sun to ‘Brilliant’ 6-8 in. Well drained Crimson May-July Dark green; carpet-like habit. part shade Brilliant Maiden Pink Dianthus gratianopolitanus ‘Firewitch’ 6-8 in. Sun Well drained Deep pink May-June Gray-green grass-like foliage. ’Spotty’ 6-8 in. Sun Well drained Rose-red with May-June Gray-green grass-like foliage. white spots

‘Tiny Rubies’ 4-6 in. Sun Well drained Deep pink May-June Pin cushion growth habit with double flowers. Dianthus plumarius Red, pink, 6-12 in. Sun Well drained May-June Several varieties. Cottage pink white Dry, well Eriogonum umbellatum 6-12 in. Sun Umbrella-like flowers; evergreen mounds of drained Yellow May-July Yellow sulfur flower foliage turn reddish in fall. Dry, well Yellow May-July Folliage turns red in fall, Plant Select® 2007. Kannah Creek® 6-12 in. Sun drained Gazania krebsiana Dry, well May need some winter protection. 4-6 in. Sun Orange May-Sept. Tanager® Gazania drained Plant Select® 2003. Geranium x cantabrigiense Cambridge Cranesbill 6-12 in. Sun to part Well drained Bright pink May-July Spreading, mounded form; foliage turns wine ‘Biokovo’ 4-10 in. shade Well drained White-pink May-July red in fall. Biokovo Cranesbill Sun to part Trailing groundcover; foliage turns red in fall. shade Geranium cinereum ‘Ballerina’ Sun to part 4-8 in. Well drained Pink-purple May-Aug. Deeply divided bright green foliage. Ballerina Grayleaf shade Cranesbill Geranium dalmaticum Sun to part Compact Rose 4-6 in. Well drained Rose-pink May-July Dense spreading foliage turns red in fall. shade Cranesbill Geranium magniflorum Sun to part Lacy, dark green foliage turns purplish-red in LaVeta Lace® 6-10 in. Well drained Purple May-July shade winter. Plant Select® 2003. Cranesbill Gypsophila repens 4-8 in. Sun Well drained White or pink June-July Mat-like habit. Creeping baby’s breath Helianthemum nummularium 8-12 in. Sun Dry, well Pink May-June Mounded habit, silvery foliage. Sunrose drained ‘Wisley Pink’ ‘Wisley Primrose’ 8-12 in. Sun Dry, well Yellow May-July Mounded habit, silvery foliage. drained Heuchera sanguinea 8-18 in. Sun to part Dry, well Red May-July Green foliage, bell-shaped flowers. ‘Firefly’ shade drained Firefly Coral Bells ‘Snow Angel’ 8-18 in. Part shade Dry, well Pink-red May-July Variegated foliage. Plant Select® 2003. Snow Angel Coral Bells drained Iberis sempervirens Sun to part May-June 8-12 in. Well drained White Evergreen foliage. Candytuft shade Iris x pumila Dry, well Blue or Short, stiff clump-forming leaves, several 8-12 in. Sun May-June Dwarf Iris drained yellow varieties. Linum flavum ‘Compactum’ 10-15 in. Sun Well drained Yellow May-July Dark green foliage. Dwarf golden flax Nepeta x ‘Psfike’ Low, spreading growth habit. Plant Select® 8-12 in. Sun Well drained Lavender June-Sept. Little Trudy® catmint 2008. Oenothera speciosa 8-12 in. Sun Well drained Pink to white June-Sept. Day-flowering. White evening primrose (Table 1, Continued) Table 1: Recommended rock garden plants.

Soil Flower Bloom Plant Name Height Exposure Remarks Preference Color Period Osteospermum barberiae ‘Compactum’ Sun to part Evergreen clumps of foliage. 8-12 in. Well drained Purple April-Aug. Purple Mountain® shade Plant Select® 1998. Sun Daisy

Osteospermum spp. Evergree clumps of foliage. Plant Select® 8-12 in. Sun Well drained White April-Aug. 'Avalanche'PPAF sun daisy 2011.

Osteospermum spp. Sun to part White to Evergreen clumps of foliage. Lavender Mist® 8-12 in. Well drained April- Aug. shade lavender Plant Select® 1998. Sun Daisy Penstemon caespitosus 3-6 in. Sun Well drained Blue May-June Mat-like; dark green foliage. Creeping penstemon Penstemon pinifolius Needle-like evergreen foliage, trumpet- Pineleaf penstemon 6-12 in. Sun Dry Orange-red June-Sept. shaped flowers.

‘Mersea Yellow’ 6-12 in. Sun Dry, well Yellow June-Sept. Needle-like evergreen foliage, trumpet- drained shaped flowers. Phlox subulata Pink, white, Several varieties based on flower color; may Moss pink or creeping 4-6 in. Sun Well drained April-May lavender winterburn. phlox Potentilla nepalensis ‘Miss Wilmott’ 8-12 in. Sun Well drained Pink to red May-July Strawberry-like leaves on clump plants. Miss Wilmott cinquefoil Prunella laciniata Sun to part 8-12 in. Moist Pink May-June Dark green fuzzy leaves, mat-forming. Lacy Self Heal shade Blue to Pulsatilla vulgaris Sun to part Silky leaves appear after flowering, followed 6-12 in. Well drained purple, red, March-April Pasque Flower shade by long-lasting feathery seedheads. white Saponaria ocymoides 6-10 in. Sun Well drained Pink May-July Shear after bloom; evergreen mat-like foliage. Rock soapwort Saxifraga oppositifolia Sun to ‘Purple Robe’ 6-10 in Well drained Purple June-Sept. Bright green mounds, cup-shaped flowers. part shade Purple Robe saxifrage Sedum spp. Variable Any, well Varies with Some evergreen; some more appropriate as Sun July-Oct. Stonecrop 1-15 in. drained species ground covers. Sedum acre Dry, well Evergreen leaves, fast spreading, 2-4 in. Sun Yellow May-June Gold Moss stonecrop drained star-shaped flowers. Sedum spurium Dry, well ‘Dragon’s Blood’ 2-4 in. Sun drained Rose red June-July Evergreen foliage with red edge, turns red in fall. ‘Red Carpet’ 2-4 in. Sun Dry, well Rose red June-July Red, wedge-shaped evergreen foliage. drained Sempervivum spp. 1-6 in., Houseleek flower Sun Dry, gravelly Pink to red July-Sept. Succulent, evergreen foliage in rosettes. Hen and chicks taller Stachys byzantina Infertile, well Not Not ‘Silver Carpet’ 6-12 in. Sun Rarely flowers; velvety silver foliage. drained important important Silver Carpet Lamb’s Ear Teucrium chamaedrys 6-12 in. Sun Well drained Purple-pink July-Aug. Evergreen; cut back after flowering. Germander Thymus x citriodorus Dry, well 4-12 in. Sun Pink June-July Lemon-scented foliage. Lemon thyme drained Thymus praecox Infrequent, Dry, well ‘Pseudolanuginosus’ 1-3 in. Sun pink and June-July Woolly-gray foliage turns purplish in winter. drained Woolly thyme purple Thymus praecox articus 1-4 in. Sun Dry, well Purple June-July Aromatic foliage; mat-forming. drained

Mother-of-thyme 1-3 in. Sun Dry, well Pink May-June Pink flowers over mat-like foliage. drained Verbena bipinnatifida Dry, well Trailing stems with deeply cut leaves. Valley Lavender® 3-6 in. Sun Purple June-Aug. drained Plant Select® 2005. verbena (Table 1, Continued) Table 1: Recommended rock garden plants.

Soil Flower Bloom Plant Name Height Exposure Remarks Preference Color Period Veronica liwanensis Dry, well Dense mat of small dark green foliage. Plant 1-2 in. Sun Blue May-June Turkish speedwell drained Select® 1997. Veronica pectinata Dry, well Blue to Woolly speedwell 1-2 in. Sun drained purple May-July Gray, mat-like foliage turns purplish in winter. Veronica prostrata Sun to 2-6 in. Well drained Blue May-June Dense mats, dark green foliage. Prostrate speedwell part shade Veronica repens 1-3 in. Part shade Well drained Blue May-June Mat-like habit. Creeping speedwell Veronica x hybrida Sun to part Evergreen, small rounded leaves. Crystal River® 1-3 in. Well drained Blue May-June shade Plant Select® 2003. speedwell Viola cornuta Sun to part 4-10 in. Moist Purple April-July Tufts of dark green foliage. Horned violet shade Viola corsica Sun to part Tufts of dark green foliage. 6-8 in. Moist Purple April- Sept. Corsican violet shade Plant Select® 2003. Zauschneria garrettii ‘Orange Carpet’ Dry, well Reddish- Mounded growth habit with trumpet-shaped 4-10 in. Sun Aug.-Sept. Orange Carpet® drained orange flowers. Plant Select® 2001. California Fuchsia Zinnia grandiflora Dry, well 4-8 in. Sun Yellow June-Sept. Flowers turn papery and last into winter. Rocky Mountain Zinnia drained

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