Maritime Pacific Northwest

    Our Maritime Pacific Northwest region covers an extensive area with a climate characterized by relatively high precipitation, long, cool summers and somewhat mild winters. The southern parts – roughly from Vancouver southward – experience dry summers, while the northern regions, due to the influence of cold ocean currents, have no dry season. This generalization is complicated, however, by rain-shadows and microclimates created by the numerous mountains in the area.

• Good Plants for the Beginning Rock Garden
• Good Doers in High-Precipitation Areas of the Pacific Northwest

Good Plants for the Beginning Rock Garden

Aethionema grandiflorum

Tiny shrubby plants produce masses of fragrant light pink flowers in spring. They will self-sow widely if you don’t shear them after flowering. Needs: sandy, gritty soil, excellent drainage, full sun.

Alyssum species

Don’t plant “basket of gold” (Aurinia saxatilis, often called “alyssum”). Choose some of the tiny, silver-leaved, yellow-flowered species, many from Turkey, such as A. propinquum and A. tortuosum. Grow them from seed from the NARGS Seed Exchange – they will germinate in a week or two in moderately warm conditions.

Aquilegia flabellata ‘Nana’

Miniature columbines in blue and white. Seed from the Seed Exchange may produce a wide variety of forms because columbine hybridize in the garden, but these are so easy to grow you can pick out the keepers. Suitable for any site with moderately good drainage.

Calluna vulgaris ‘Sister Anne’

A very slow, mat-forming, silver-leaved heather. Needs: Some summer water, moderate drainage, full to half-day sun.

Campanula ‘Birch Hybrid’

Moderate growth rate, bright lavender-blue flowers, and no seedlings. Suitable for the rock garden or dry wall. Widely sold.

Campanula cochlearifolia

Tiny mat plant, spreads underground. Try to get a single-flowered selection, not the double forms. Needs: Moderate drainage, full to half-day sun, tolerates summer water.

Daphne cneorum (sold as “rock daphne”)

Low, spreading shrubs with bright pink fragrant flowers. ‘Eximia’ is a good variety widely available; many other named forms can be obtained from specialist nurseries. Needs excellent drainage, full sun, and no disturbance after planting.

Dianthus cushion-forming varieties

Look for “pinks” that grow as tight cushions and mats, such as ‘Little Jock’, ‘Inshriach Dazzler’, and ‘Tiny Rubies’. The plant widely sold as Dianthus simulans may be misnamed; it forms an impressive cushion but flowers sparsely.

Epilobium canum

Much better known under its former name Zauschneria. Numerous selections bear fiery scarlet flowers in late summer (pale forms are not so showy). Spreads underground and can take too much room, so best for larger sites or confined. Dormant in winter. Needs: full sun, good drainage; tolerates but doesn’t need summer water.

Erodium cheilanthifolium

This and hybrids of similar appearance form spherical mounds and flower for a long period. Needs: Good drainage, full sun.

Gentiana septemfida

The easiest gentian here. Small deep blue flowers in late summer. Needs: moderate drainage, summer water, full to half-day sun.

Geranium dalmaticum

A tiny pink hardy geranium that will not cause you trouble by seeding (most others would). Spreads slowly underground. Needs: Moderate drainage, full sun; tolerates summer water but doesn’t need it.

Helianthemum nummularium

Many varieties of “sun rose” are available. Shear them after flowering to keep compact. Needs: Good drainage, full sun; tolerates but doesn’t need summer water.

Iris, Miniature Dwarf Bearded

Seek the tiniest selections from iris nurseries for a nice contrast on the garden. You may eventually move on to species. Needs: Moderate drainage, full sun; tolerates but doesn’t need summer water.

Iris tenax

The hardiest of the Pacific Coast irises (there are also hundreds of beautiful hybrids available from specialist iris nurseries). Great for holding a slope and contrast with heathers. Needs: Moderate drainage, full sun, little summer water.

Leucanthemum weyrichii (aka Chrysanthemum weyrichii)

Low plants creep between rocks and bear big pink or white daisies in summer. Needs: good drainage, cool root run, sun, some summer water.

Lewisia cotyledon

Native to the Siskiyou Mountains of southern Oregon and northern California. Requires very good drainage and at least half-day sun. Succeeds best if you buy very small plants and get them in the ground right away; big, flowery nursery plants are likely to have been forced in greenhouses and rarely settle into the garden in healthy condition. Easily grown from seed, too.

Lithodora diffusa

Widely planted groundcover shrub with deep blue flowers in spring to summer. Suitable if you have plenty of space, which it will cover fast. You can grow bulbs through it. Needs: Moderate drainage, full sun; tolerates but doesn’t need summer water.

Origanum ‘Kent Beauty’

Drooping flowering stems look perfect above a rock or atop a wall in late summer. ‘Barbara Tingey’ is similar. Needs: full sun, good drainage; tolerates but doesn’t need summer water. (Never plant the tall oreganos such as ‘Herrenhausen’ in a rock garden, they are invasive.)

Paronychia argentea and related species.

Slowly expanding flat mats of silvery foliage, papery everlasting floral bracts. Needs: good drainage, full sun, little or no summer water.

Penstemon rupicola

Native to the Pacific Northwest with gray leaves and brilliant pink flowers. Requires very good drainage, little or no summer water, and flowers best in full sun. Choose well-rooted small plants. If you can only get a big plant, set the crown 2 inches below the soil surface to induce new basal branching.

Phlox hybrids

Some may be sold as “Phlox douglasii,” a misnomer. Look for cultivars such as ‘Crackerjack’, ‘Red Admiral’, ‘May Cushion’. Don’t buy dull, loose-growing common varieties of Phlox subulata–look in specialist nurseries for compact selections.

Primula elatior

The light yellow “oxlip” one of the best perennial primulas for the PNW. Easy from seed, as is the “cowslip,” P. veris. Needs: afternoon shade, moderate drainage, some summer water.

Ptilotrichum spinosum ‘Roseum’

Sometimes called Alyssum spinosum. A low, silver-leaved shrub that once settled with good drainage and sun will produce pink flowers forever.

Pulsatilla vulgaris

The “pasqueflower” comes in many colors and forms. Small plants establish better than big ones and can live for decades. Needs: good drainage, full sun; tolerates but doesn’t need summer water.

Sedum spathulifolium

Widespread on rocky sites in the PNW, from Coast to Cascades, this mat-forming succulent tolerates sun or part shade and needs perfect drainage. ‘Cape Blanco’ is a popular variety, but many wild populations closely resemble it.

Sempervivum

“Hens and chicks” deserve a place in every rock garden. Choose those with smaller rosettes; fuzzy-leaved kinds don’t handle wet winters as well as smooth ones. Best form is achieved in full sun but they tolerate part shade and some summer water.

Veronica prostrata

Deep blue flowers on a lax mat. Needs: full sun, good drainage; tolerates summer water.

Good Doers in High-Precipitation Areas of the Pacific Northwest

Aethionema armenum ‘Warley Rose’

Low shrublet, leaves blue-grey, red tints, flowers deep pink

Alchemilla alpina

Dainty, silver-backed foliage

Alyssum spinosum

Small shrub to 24”, spiny grey mound, flowers pink or white

Androsace sempervivoides

Flat pink rosettes

Astelia nervosa

Silvery bronze spiky foliage to 10”

Aubrieta spp.

Many cushion or mat-forming forms in shades of pink & purple

Bergenia ciliata

Low waxy foliage, early pink flowers

Campanula spp.

Creeper; many selections available, flowers blue to white

Dianthus spp.

Many dwarf selections are available

Erysimum alpinum

Low mat-forming, flowers yellow, scented

Euphorbia myrsinites

Grey, textured foliage, flowers acid-green

Geranium cinereum

6”, many good cultivars, flowers pink to carmine

Globularia cordifolia

Dwarf creeping shrublet, 6”, flowers deep blue puffs

Hacquetia epipactis

Clump-forming, 6”, early spring with acid-green flowers

Hieracium lanatum

Felty grey foliage, yellow flowers in late spring–summer

Hypericum olympicum

Dwarf shrub 4” to 20”, mounds of soft yellow flowers

Iberis pruitii

Evergreen sub-shrub with twiggy foliage, white glistening flowers

Iris cristata

Dwarf iris to 6”, spreading, blue flowers

Iris, Pacific Coast hybrids

6” to 10” in many colors and shades

Phlox subulata

Forms dense mats, flowers pink to white to blue, many good cultivars available

Phyteuma nigrum

Purple-blue spikes to 10”, summer

Potentilla cinerea

Spreading dwarf to 4”, leaves grey-green above, grey below, flowers yellow

Primula x ‘Wanda’

4”, rosettes of purple-flushed leaves, deep reddish-purple flowers

Pulsatilla vulgaris

6”, basal leaves, bell-shaped pale or dark violet flowers, rarely white

Saxifraga callosa

Encrusted saxifrage, low mat of silvery rosettes, white flowers on 12” stem

Silene alpestris

Low mat of white flowers, early summer

Veronica peduncularis ‘Georgia Blue’

8” semi-prostrate, flowers blue, in spring