Plants as Design Elements: Contrast, Form, and Color

Contrast: Big Leaves
Canna; Colocasia; Darmera peltatum; Hosta; Hydrangea; Ligularia; Rodgersia

Contrast: Variegated Foliage
Athyrium niponicum var. pictum
Caladium species and cultivars
Canna ‘Pretoria’
Carex oshimensis ‘Evergold’
Cornus alba ‘Elegantissima’
C. sericea ‘Silver and Gold’
Euonymus fortunei ‘Emerald Gaiety’
Hosta ‘Patriot’
Hydrangea macrophylla ‘Mariesii Variegata’
Ilex aquifolium ‘Aurea Marginata’
Iris ensata ‘Variegata’
I. pallida ‘Argentea Variegata’
L. Silvery Sunproof (L. muscari ‘Variegata’)
Miscanthus sinensis ‘Variegatus’
Polygonatum odoratum var. pluriflorum ‘Variegatum’
Pulmonaria saccharata ‘Mrs. Moon’
Solenostemon (coleus) cultivars
Weigela ‘Florida Variegata’
Yucca filamentosa ‘Color Guard’

Form: “Minarets”
Many plants in the garden naturally form rounds, or “domes,” but fewer plants serve as verticals, or “minarets.” I list here some of my favorite plants to use as vertical elements in garden design.

Agastache ‘Black Adder’
Allium species
Cynara cardunculus
Digitalis purpurea
Eremurus species and cultivars
Gladiolus murielae
Ilex crenata ‘Sky Pencil’
Juniperus communis ‘Compressa’
J. scopulorum ‘Wichita Blue’
Kniphofia ‘Alcazar’, ‘Little Maid’, ‘Percy’s Pride’
Persicaria bistorta ‘Superba’
Thuja occidentalis ‘Smaragyd’
Verbascum bombyciferum ‘Polarsommer’ (biennial)

Color

Dark Red Foliage
Acer palmatum ‘Bloodgood’
A. palmatum var. dissectum ‘Garnet’, ‘Tamukeyama’
Actaea simplex Atropurpurea Group
Alternanthera dentata ‘Rubiginosa’
Berberis thunbergii ‘Crimson Pygmy’
Canna ‘Australia’, ‘King Humbert’
Cordyline australis ‘Red Sensation’
Cotinus coggygria ‘Royal Purple’
Dahlia ‘Fascination’
Euphorbia cotinifolia
Heuchera ‘Plum Pudding’
Hibiscus acetosella ‘Red Shield’
Imperata cylindrica ‘Rubra’
Pennisetum setaceum ‘Rubrum’
Penstemon digitalis ‘Husker Red’
Prunus × cistena
Solenostemon ‘Red Carpet’

Grays and Silvers
Artemesia ‘Powis Castle’
A. ludoviciana ‘Silver Queen’
Centaurea gymnocarpa
Cynara cardunculus (biennial)
Lavandula angustifolia ‘Hidcote’
Nepeta racemosa ‘Walker’s Low’
Perovskia atriplicifolia
Plectranthus argentatus
Santolina chamaecyparissus
Stachys byzantina ‘Countess Helen Von Stein’
Verbascum bombyciferum ‘Polarsommer’ (biennial)

Blues
Aconitum carmichaelii
Agastache ‘Black Adder’
Ageratum houstonianum ‘Blue Horizon’
Anemone blanda ‘Blue Star’
Baptisia australis
Browallia americana
Brunnera macrophylla
Campanula lactiflora ‘Pritchard’s Variety’
Chionodoxa luciliae
Festuca glauca ‘Elijah Blue’
Geranium ‘Brookside’, ‘Johnson’s Blue’, ‘Jolly Bee’
Helictotrichon sempervirens
Hibiscus syriacus Blue Bird, ‘Blue Satin’
Hyacinthoides hispanica
Hydrangea macrophylla ‘Blue Wave’, ‘Enziandom’, ‘Nikko Blue’
H. serrata ‘Blue Billow’
Juniperus squamata ‘Blue Star’
Muscari armeniacum
Nepeta racemosa ‘Walker’s Low’
N. sibirica ‘Souvenir d’Andre Chaudron’
N. subsessilis
Picea pungens ‘Montgomery’
Platycodon grandiflorus
Plectranthus ‘Mona Lavender’
Ruellia brittoniana
Salvia guaranitica ‘Black and Blue’
S. ‘Indigo Spires’
S. × sylvestris ‘Blauhügel’ (Blue Hill), ‘Ostfriesland’, ‘Mainacht’ (May Night)
Scaevola aemula ‘Blue Wonder’
Scilla siberica
Tibouchina urvilleana
Vitex agnus-castus

Yellows
Achillea ‘Moonshine’
Acorus gramineus ‘Ogon’
Amsonia hubrichtii (fall foliage color)
Berberis thunbergii ‘Aurea’
Carex elata ‘Aurea’
Chamaecyparis pisifera ‘Golden Mop’
Coreopsis verticillata ‘Moonbeam’ 
Corylopsis pauciflora
Geum ‘Lady Stratheden’
Helianthus argophyllus ‘Japanese Silver Leaf’
Helianthus augustifolius
Heliopsis helianthoides var. scabra ‘Prairie Sunset’, Summer Sun H.
Hemerocallis ‘Happy Returns’,‘Hyperion’
Jasminum nudiflorum
Kirengeshoma palmata
Kniphofia ‘Little Maid’, ‘Percy’s Pride’
Lilium Citronella Group
Melampodium paludosum ‘Lemon Delight’
Nicotiana langsdorffii
Rudbeckia lacinata ‘Herbstsonne’
R. maxima
Solidago rugosa ‘Fireworks’
Spiraea japonica ‘Golden Elf’, ‘White Gold’
S. thunbergii ‘Ogon’
Yucca filamentosa ‘Color Guard’

Reds and Oranges
Begonia ‘Bonfire’
Begonia × hybrida ‘Dragon Wings’
Bouvardia ternifolia
Crocosmia ‘Lucifer’
Cuphea ‘David Verity’
Geum ‘Fire Opal’,‘Mrs. J. Bradshaw’
Gomphrena ‘Strawberry Fields’
Hemerocallis ‘Poinsettia’
Hibiscus moscheutos ‘Lord Baltimore’
Kniphofia ‘Alcazar’
Lantana camara ‘Miss Huff’
Lilium canadense
L. henryi
Lychnis chalcedonica
Persicaria amplexicaulis ‘Firetail’, ‘Atrosanguineus’
Salvia coccinea ‘Lady in Red’
Spiraea japonica ‘Goldflame’(orange spring foliage)
Tithonia rotundifolia ‘Fiesta del Sol’, ‘Torch’  

Pinks
Allium cristophii
Anemone tomentosa ‘Robustissima’
Astilbe chinensis var. taquetii ‘Superba’
Dahlia ‘Fascination’, ‘Onesta’
Digitalis purpurea (biennial)
Echinacea purpurea
Eupatorium maculatum ‘Gateway’
Geranium macrorrhizum
Gomphrena ‘Lavender Lady’
Helleborus × hybridus
Hibiscus moscheutos ‘Lady Baltimore’
Lespedeza thunbergii ‘Pink Fountain’
Lilium speciosum var. rubrum
Magnolia × soulangeana
Nicotiana mutabilis
Pennisetum alopecuroides ‘Karley Rose’
Persicaria bistorta ‘Superba’
Phlox paniculata ‘Bright Eyes’
Rosa ‘Betty Prior’, Simplicity (pink form)
R. glauca (R. rubrifolia)
Salvia splendens ’Van-Houttei’
Sedum cauticola ‘Lidakense’
S. Autumn Joy
Thalictrum rochebruneanum ‘Lavender Mist’