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Rock Garden Plants – 7.401   arrow

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by J.E. Klett and R.A. Cox * (7/11)

Quick Facts…

  • Rock gardens are effective if built on a natural slope or terrace.
  • Use rocks of one geological type.
  • Good drainage is necessary.
  • Plant a variety of species in the rockery.
  • The garden should not be larger than can be easily maintained.

The ideal location for a rock garden is a natural slope or terrace, such as those found at the side or rear of a house based on a split-level or garden-level design.

Use rocks of one geological type. A common rock in Colorado is native granite covered with lichens (moss rock). Rocks are available from nurseries, landscape contractors and rock dealers. An effective rock garden should have several large rocks, some weighing 200 pounds or more.

Set the rock into the ground so at least one-third is buried. Place rocks in a natural way, following the grain of the rock. Position rocks to control soil erosion between rocks and to allow soil pockets of various sizes for plants. Use smaller, similar rock as a mulch. Place lichen-covered rock to expose as much of the lichen as possible.

Provide good drainage. Most plants suitable for rock gardens require a well-drained soil. For most plants, incorporate organic matter into heavier clay soils to improve texture and provide better drainage. Refer to fact sheet 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.

Plant a variety of species, repeating some species several times to make the garden look natural. Ideally, rock garden plants should spread slowly. Take care not to overplant.

PlantSelect

Plant Selection

Many types of plants are suitable for rock gardens. Generally, plants that are low growing and have a clumping habit are preferred. Perennial plants are most common in rock gardens, although some annuals can be used. Table 1 lists many rock garden plants, along with their characteristics and cultural requirements. Most plants listed should be hardy to 8000 feet, some higher. Refer to fact sheets 7.406, Flowers for Mountain Communities and 7.413, Ground Covers for Mountain Communities.

Plant Select® plants may be viewed online at www.plantselect.org.

2008.

2008.

Table 1: Recommended rock garden plants.
Plant Name Height Exposure Soil
Preference
Flower
Color
Bloom
Period
Remarks
Ajuga reptans
      Carpet bugle

      ‘Atropurpurea’

      ‘Burgundy Glow’

      ‘Chocolate Chip’

4-10 in.

4-6 in.

4-6 in.

2-4 in.

Shade to part shade
Shade to part shade
Shade to part shade
Shade to part shade
Well drained

Well drained

Well drained

Well drained

Blue, purple

Violet-blue

Blue

Blue

May-June

May-June

May-June

May-June

Spreading ground cover.

Bronze-purple foliage.

Pink, white and green foliage.
Wavey,chocolate-brown foliage

 
Alyssum montanum
      Mountain alyssum
4-10 in. Sun Dry, rocky Yellow April-May Gray foliage.
 
Arabis caucasica
      ‘Snowcap’
      Snowcap
      rockcress

6-9 in.

Sun

Well drained

White

April-May

Abundant white flowers over gray foliage.
 
Arctostaphylos
uva-ursi

      Kinnikinick

      ‘Massachusetts’

6-8 in.

4-6 in.

Shade to part sun

Shade to part sun

Acid to neutral,high in humus,well drained
Acid to neutral,high in humus,well drained

White-tinged red
Pink-tinged

May-June

April-May

Spreading evergreen foliage; red fruits.
Spreading evergreen foliage; red fruits.

 
Armeria maritima
      Sea Pink

      ‘Victor Reiter’

4-10 in.

2-4 in.

Sun

Sun

Dry, well drained

Dry, well drained

Pink, white,purple

Pink

May-June

April-June

Grass-like foliage; several varieties.

Small mounded plant.

 
Aubrieta deltoidea
      ‘Purple Gem’
      Purple Gem
          Rockcress
4-6 in. Sun to part shade Well drained Purple April-June Mounded to spreading; shear after bloom.
 
Aurinia saxatilis
      Basket-of-gold
8-12 in. Sun Dry, rocky Yellow April-May Grayish-green foliage; shear after bloom.
 
Campanula carpatica
      Carpathian
      harebell
     ‘Blue Clips’

     ‘White Clips’

8 in.
6-12 in.

6-12 in.

Sun
Sun to part shade

Sun to part shade

Well drained
Well drained

Well drained

Blue-Lilac
Blue

White

June-July
June-July

June-July

Bright green foliage.
Compact mound of bright-green foliage.
Compact mounds of wavy, bright green foliage.
 
Campanula poscharskyana
      Serbian bellflower

6-8 in.

Sun to part shade

Well drained

Blue

June-Aug.

Prolific flowers.

 
Campanula rotundifolia
      Bluebell

8-12 in.

Part shade

Well drained

Blue

May-Sept.

Bell-like flowers on slender stems.
 
Cerastium tomentosum
      Snow-in-summer

4-10 in.

Sun

Dry, well drained

White

May-June

Aggressive; shear after bloom.
 
Ceratostigma plumbaginoides
      Plumbago

8-12 in.

Sun topart shade

Well amended

Blue

Aug.-Sept.

Foliage turns red in fall.

 
Coreopsis auriculata
‘Nana’
      Dwarf Coreopsis

4-8 in.

Sun

Dry and well drained

Orange-Yellow

June-Sept

Dense compact spreading mounds.
 
Delosperma cooperi
      Purple ice plant
2-3 in. Sun Well drained Purple June-frost Succulent foliage; to 7000’.
 
Delosperma dyeri
      Red Mountain®
      ice plant

1-2 in.

Sun

Dry, well drained

Orange-red

June-Sept

Succulent leaves, carpet-like. Plant Select®2007.
Delosperma floribundum
      Starburst®
      ice plant

4-6 in.

Sun

Dry, well drained

Pink with white centers

June-Sept

Succulent leaves, clump form. Plant Select®1998.
 
Delosperma nubigenum
     
Yellow ice plant

2-3 in.

Sun

Well drained

Yellow

May-June

Succulent foliage turns reddish-purple in winter.
 
Delosperma x ‘Kelaidis’
      Mesa Verde®
      ice plant

2-4 in.

Sun

Dry, well drained

Salmon pink

June-Sept

Succulent leaves, carpet-like.Plant Select®2002.
 
Delosperma x ‘John Proffit’
      Table Mountain®
      ice plant

2-4 in.

Sun

Dry, well drained

Pink-purple

June-Sept

Succulent leaves, carpet-like. Plant Select®2002.
 
Delosperma ‘Pstave’
      Lavender
      Ice™ ice plant
2-4 in. Sun Dry, well drained Pink-lavender June-Sept Succulent leaves. Plant Select®2009
Dianthus deltoides
      ‘Brilliant’
      Brilliant Maiden
      Pink
6-8 in. Sun to part shade Well drained Crimson May-July Dark green; carpet-like habit.
 
Dianthus gratianopolitanus
      ‘Firewitch’

      ’Spotty’

      ‘Tiny Rubies’

6-8 in.

6-8 in.

4-6 in.

Sun

Sun

Sun

Well drained

Well drained

Well drained

Deep pink

Rose-red with white spots
Deep pink

May-June

May-June

May-June

Gray-green grass-like foliage.
Gray-green grass-like foliage.
Pin cushion growth habit with double flowers.

 
Dianthus plumarius
      Cottage pink
6-12 in. Sun Well drained Red, pink, white May-June Several varieties.
 
Eriogonum umbellatum
      Yellow sulfur
      flower
      Kannah Creek®

6-12 in.

6-12 in.

Sun

Sun

Dry, well drained

Dry, well drained

Yellow

Yellow

May-July

May-July

Umbrella-like flowers; evergreen mounds of foliage turn reddish in fall.

Folliage turns red in fall, Plant Select® 2007.

 
Gazania krebsiana
      Tanager® Gazania
4-6 in. Sun Dry, well drained Orange May-Sept. May need some winter protection. Plant Select® 2003.
 
Geranium x cantabrigiense
      Cambridge
      Cranesbill
      ‘Biokovo’
      Biokovo Cranesbill

6-12 in.

4-10 in.

Sun to part shade

Sun to part shade

Well drained

Well drained

Bright pink

White-pink

May-July

May-July

Spreading, mounded form; foliage turns wine red in fall.
Trailing groundcover; foliage turns red in fall.
 
Geranium cinereum
      ‘Ballerina’
      Ballerina Grayleaf
     Cranesbill

4-8 in.

Sun to part shade

Well drained

Pink-purple

May-Aug.

Deeply divided bright green foliage.

 
Geranium dalmaticum
      Compact Rose
      Cranesbill
4-6 in. Sun to part shade Well drained Rose-pink May-July Dense spreading foliage turns red in fall.
 
Geranium magniflorum
      LaVeta Lace®
      Cranesbill

6-10 in.

Sun to part shade

Well drained

Purple

May-July

Lacy, dark green foliage turns purplish-red
in winter. Plant Select® 2003.
 
Gypsophila repens
      Creeping baby’s
      breath
4-8 in. Sun Well drained White or pink June-July Mat-like habit.
 
Helianthemum nummularium
      Sunrose
      ‘Wisley Pink’
      ‘Wisley Primrose’

8-12 in.

8-12 in.

Sun

Sun

Dry, well drained

Dry, well drained

Pink

Yellow

May-June

May-July

Mounded habit, silvery foliage.

Mounded habit, silvery foliage.

 
Heuchera sanguinea
      ‘Firefly’
      Firefly Coral Bells
      ‘Snow Angel‘
      Snow Angel Coral
      Bells

8-18 in.

8-18 in.

Sun to part shade

Part shade

Dry, well drained

Dry, well drained

Red

Pink-red

May-July

May-July

Green foliage, bell-shaped flowers.

Variegated foliage. Plant Select® 2003.

 
Iberis sempervirens
      Candytuft
8-12 in. Sun to part shade Well drained White May-June Evergreen foliage.
 
Iris x pumila
      Dwarf Iris
8-12 in. Sun Dry, well drained Blue or yellow May-June Short, stiff clump-forming leaves, several varieties.
 
Linum flavum
      ‘Compactum’
     Dwarf
      golden flax
10-15 in. Sun Well drained Yellow May-July Dark green foliage.
 
Nepeta x ‘Psfike’
      Little Trudy®
      catmint
8-12 in. Sun Well drained Lavender June-Sept Low, spreading growth habit. Plant Select®
 
Oenothera speciosa
      White evening
      primrose
8-12 in. Sun Well drained Pink to white June-Sept. Day-flowering.
 
Osteospermum barberiae
      Purple Mountain®
     Sun Daisy

8-12 in.

Sun to part shade

Well drained

Purple

April-August

Evergreen clumps of foliage. Plant Select®
1998.
 
Osteospermum spp.
      ‘Avalanche’PPAF
      sun daisy
8-12 in. Sun Well drained White to lavender April-August Evergreen clumps of foliage. Plant Select®
1998.
Osteospermum spp.
      Lavender Mist®
      Sun Daisy
8-12 in. Sun to part shade Well drained White to lavender April-August Evergreen clumps of foliage. Plant Select®
1998.
 
Penstemon caespitosus
      Creeping
      penstemon

3-6 in.

Sun

Well drained

Blue

May-June

Mat-like; dark green foliage.

 
Penstemon pinifolius
    Pineleaf penstemon
    ‘Mersea Yellow’
6-12 in.

6-12 in.
Sun

Sun
Dry

Dry, well drained
Orange-red

Yellow
June-Sept

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

Mother-of-thyme
1-4 in.

1-3 in.

Sun

Sun

Dry, well drained

Dry, well drainer

Purple

Pink

June-July

May-June

Aromatic foliage; mat-forming.
Pink flowers over mat-like foliage.
 
Verbena bipinnatifida
      Valley Lavender®
      verbena
3-6 in. Sun Dry, well drained Purple June-Aug. Trailing stems with deeply cut leaves.
Plant Select® 2005.
 
Veronica liwanensis
      Turkish speedwell
1-2 in. Sun Dry, well drained Blue May-June Dense mat of small dark green foliage. Plant Select®
1997.
 
Veronica pectinata
      Woolly speedwell
1-2 in. Sun Dry, well drained Blue to purple May- July Gray, mat-like foliage turns purplish in winter.
 
Veronica prostrata
      Prostrate
      speedwell
2-6 in. Sun to part shade Well drained Blue May-June Dense mats, dark green foliage.
 
Veronica repens
     Creeping
      speedwell
1-3 in. part shade Well drained Blue May-June Mat-like habit.
 
Veronica x hybrida
      Crystal River®
      speedwell
1-3 in. Sun to part shade Well drained Blue May-June Evergreen, small rounded leaves.
Plant Select® 2003.
 
Viola cornuta
      Horned violet
4-10 in. Sun to part shade Moist Purple April-July Tufts of dark green foliage.
 
Viola corsica
      Corsican violet
6-8 in. Sun to part shade Moist Purple April-Sept Tufts of dark green foliage. Plant Select®
2003.
 
Zauschneria garrettii
      ‘Orange Carpet’
      Orange Carpet®
      California
      Fuchsia

4-10 in.

Sun

Dry, well drained

Reddish-orange

Aug.-Sept.

Mounded growth habit with trumpet-shaped flowers. Plant
Select® 2001.
 
Zinnia grandiflora
      Rocky Mountain

      Zinnia
4-8 in. Sun Dry, well drained Yellow June-Sept. Flowers turn papery and last into winter.

*J.E. Klett, Colorado State University Extension horticulture specialist and professor, horticulture and landscape architecture; and R.A. Cox, Extension horticulture agent, Arapahoe County. 6/00. Revised 7/11.

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