MeetingsQuestions?PublicationsSeeds BooksGardensSlides & VideosLinksSite Map

Part II: Good Rock Garden Plants

by NARGS contributors

These plants are selected for ease of cultivation and availability. That said, most are not tolerant of arbitrary environmental choices; you ignore the cultural suggestions at your plant's peril. Moreover, what is easy in the Northwest is not necessarily easy in the Southeast.

Though we have attempted to counter our Northeast bias with review from around the country, the blame for inappropriate recommendations remains with us. Still, you can read this advice with a view towards adapting it to your own climate. If you are in Seattle and the advice is "part or full sun," choose full sun. If you are in the Rockies with a third of the Northeast's rainfall, figure out how you are going to accommodate woodland plants before you tackle them. If you are in the Piedmont, where summer heat murders alpines, the saving grace may be replacing "full sun" with afternoon shade.

USDA ratings are given for the minimum and maximum Zones where these plants grow well. (If you don't know your Zone, ask your county extension agent.) The high end was chosen to reflect the rigorous heat and humidity of the Southeast. If you are subject to a drier or more moderate climate, you can stretch the upper limits.

No matter what you do, you will have failures; all rock gardeners do. When that happens, look at the brethren of the recently deceased in rock gardens near you. Note the differences in cultural conditions; ask what's under the gravel mulch; ask about the pH factor of the soil; ask about watering. Use the local chapter of the American Rock Garden Society for access and invitations.

Where do you get these plants? Even in a list like this, chosen for availability, only a smattering will be at your local garden center. You'll have to seek them out, and again your local chapter of the ARGS will have suggestions; they may have a plant sale, and they may even have included an insert giving sources with this pamphlet.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Acantholimon [ah-kan-tho-ly-mon]. This handsome evergreen perennial, a native of Turkey, does well on sunny slopes, in scree beds, the alpine house, and, sometimes, in the open garden. The needle-like foliage makes a fine background for pink summer flowers, which are followed by papery bracts. The plant makes a compact mat, and will grow comfortably in Zones 6-9, and sometimes even in Zones 4 and 5. The acantholimons grow wild from Greece eastward to Asia and several varieties are well known. A. glumaceum [gloo-mah-see-um], native to Russia, has deep rose pink flowers and is the easiest species to grow.

Achillea ageratifolia [ah-kil-lee-ah a-ge-ra-ti-fo-lee-ah]. (syn. A. serbica). Profuse 1" white daisies in May on 6" stems above a creeping mat of silvery, felted, lance-shaped leaves. Sun, well-drained soil, scree or between paving stones. From mountains in Greece and the Balkans. Zone 5.

Achillea tomentosa [toe-men-toe-sa]. Yellow flowers on 6" stems over downy, wooly, finely cut aromatic foliage. Tough and dependable. Can be mowed. There exists a fine dwarf form 'Aurea'. Full sun, good drainage. Eurasia. Zones 2-8.

Adiantum venustum [a-dee-an-tum ve-new-stum]. A Maidenhair Fern with 6-12" triangular fronds that are brilliant soft green in spring, bluish green when mature. Spreads fairly rapidly; good wall plant. Likes rich, humusy soil, and should not be planted too deeply. Himalayas. Zones 2-8.

Aethionema armenum [eeth-ee-oh-nee-ma ar-mee-num]. Shrublet with gray-blue foliage and spikes of soft pink flowers in late spring. The hybrid cultivar 'Warley Rose' is especially nice, with deep pink flowers. Grows in full sun in well-drained soil. Prolific bloomer. 3-8". Fragrant. Asia Minor. Zones 5-8.

Alchemilla alpina [al-keh-mil-lah al-pie-nah]. Foliage is green on top, silvery underneath, and more attractive than the short sprays of green-tinged flowers in spring. Sun or partial shade, in well-drained but moisture-retentive soil. Good wall plant. 6-8" high. Europe. Zones 3-7. A. saxatilis [sachs-a-til-lis] is similar and even easier.

Alyssum saxatile [ah-lis-sum sachs-sah-ta-lee]. (syn. Aurinia saxatilis). Basket of Gold. Clouds of tiny yellow flowers in May, very floriferous. Up to 6" with strap-shaped silvery foliage but can spread to 2'. The cultivar 'Citrinum' is pale yellow and combines better with other spring flower colors. Europe. Zones 3-7.

Allium thunbergii 'Ozawa' [al-ee-um thun-ber-jee-eye]. Strap-like leaves, bright rosy purple flowers on 8-12" stems. Likes moist, well-drained soil and half-day of sun. Late-blooming treasure from Japan. Zones 2-8.

Anacyclus pyrethrum var. depressus [an-ah-cy-klus pie-ree-thrum de-press-us]. (Commonly known simply as A. depressus). Mt. Atlas Daisy, 3-6", grows in a well-drained sunny location. White daisy-like flowers, with red underside, in May-June, so it opens white and closes red over gray-green filigree foliage. Morocco. Zones 5-8.

Androsace lanuginosa [an-dross-ah-see lah-noo-gi-noh-sa]. A summer-flowering trailing species, with wooly leaves and umbels of pale pink flowers. 3-4". Likes a light sandy soil and afternoon shade in the Southeast. Himalayas. Zones 4-8.

Androsace sarmentosa [sar-men-toe-sah]. Perennial rosettes, slightly hairy leaves. Umbels of pink flowers with yellow eyes in late spring. Sun or partial shade. Limy scree. 4-6" high, slowly spreads via strawberry-like runners to 2'. The overwintering form has tight, small rosettes. The variety 'Chumbyi' is densely tufted and hairy. Himalayas. Zones 2-8.

Anemone nemorosa [ah-nem-oh-nee nem-oh-roh-sa]. European Wood Anemone. A few inches high. Many colored formswhite, red, lavender, and blue. Deeply cut leaves. A fine spring ephemeral for the woodland. Place in an undisturbed location as it goes dormant at the end of June. It may take two or three years to establish, but will spread rapidly if well-sited. Zones 3-8.

Anemone sylvestris [sill-vess-tris]. Clump-forming perennial, with tufts of dark leaves. Fragrant, nodding 2" white flowers in late spring. Grows in partial shade in humus-rich conditions. 6-15" high. Eurasia. Zones 2-7.

Anemonella thalictroides [ah-nem-oh-nell-ah tha-lick-troy-i-dees]. Tuberous-rooted perennial with delicate 3-lobed leaflets. Single, white flowers. Double forms and pink-flowered forms also exist. A favorite Northeastern woodland native. Humus-rich soil. 4-10" high. Zones 4-8.

Antennaria dioica [an-ten-nay-ree-ah dye-oh-ee-ka]. Pussytoes is a mat-forming perennial with wooly, gray leaves, white underneath and bears heads of gray everlasting flowers in mid-spring. Full sun, no competition and dry, lean soil. There are forms with pink or reddish coloring. 2-4" high. Circumpolar. Zones 3-8.

Aquilegia bertolonii [a-kwi-lee-jee-ah ber-toe-low-nee-eye]. One of the best of the columbines for the rock garden. Dark green leaves. Large, rich purple flowers in May with incurved spurs on 3" stems. Woodland or cool scree. Southern Europe. Zones 3-8.

Aquilegia canadensis [kan-uh-den-sis]. A 1-2' columbine. Spring flowers, with scarlet sepals and yellow petals ending in scarlet spurs. Sun or half shade. Cultivar 'Nana' is better proportioned for the rock garden. Nova Scotia to Florida, west to Minnesota. Zones 2-8.

Aquilegia flabellata [fla-bell-lah-tah]. Short-spurred blue and white flowers on 8-10" stems in early summer. Light green glaucous foliage. There are dwarf ('Nana', 3") and larger white-flowering ('Alba') cultivars. Japan. Zones 2-9.

Arabis caucasica [ar-ah-biss kaw-kah-si-ka]. 8-14", white fragrant flowers on loose racemes in early spring. There is a magenta and a double white form. Caucasus. Zones 3-8.

Arabis procurrens [pro-cur-rens]. (Material in cultivation is often called Arabis ferdinandi-coburgii). Gray leaves. White flowers on 5" stems in spring. There is a preferred selection 'Variegata' which does best in bright shade. Bulgaria. Zones 5-8.

Arabis x sturii [times stur-ee-eye]. Neat dark green tufts of small pointed glossy leaves. Large white flowers on 3-4" stems in spring. Sun. Sparser in bloom but better in foliage than most species. Southern Europe. Zones 4-8.

Arenaria montana [a-ren-air-ee-ah mon-tan-ah]. Large white flowers in June on long trailing stems with narrow lance-shaped leaves. Forms low mounds. Sun. A rather fast grower which can spread 2' in one season. Alps. Zones 5-8.

Armeria juniperifolia [ar-mer-ee-ah ju-nip-er-i-fo-lee-ah]. (syn. A. caespitosa). Dense evergreen cushions of short rigid stems, 2" high, covered with large pink, ball-shaped flower heads. Light, well-drained soil. Good for troughs. Spain. Zones 3-8.

Armeria maritima [ma-ri-tee-mah]. Very variable in color, from white to rose, the usual form is lilac pink. Tiny flowers in rounded heads in late May. Forms a dark green grass-like mat. Brightest selection is cherry-red 'Düsseldorf Pride'. Greenland, Europe. Zones 3-8.

Asarum europaeum [ah-sah-rum you-row-peh-um]. European Ginger is an excellent, evergreen ground cover for smaller, refined areas. It likes humusy soil in part or full shade. It is approximately 4" high with shiny, kidney-shaped leaves. Zones 4-7.

Asplenium trichomanes [ah-splee-nee-um try-koh-mah-nees]. Maidenhair Spleenwort. Evergreen hardy rock fern, slender fronds 4-6" long, 3/4" wide in neat rosettes. Likes well-drained, moist, limy loam, some sun. Good wall or woodland plant. Eastern North America. Zones 3-8.

Aster alpinus [ass-ter al-pie-nus]. This is a European high alpine, perennial aster having elliptical, hairy leaves with large solitary violet flowers on 10" stems in mid-spring. It grows easily in rocky soil in full sun. It may need protection from slugs, at least when young. There are many selected forms. Zones 3-7.

Astilbe chinensis 'Pumila' [ah-still-bee chi-nen-sis pooh-mi-lah]. This member of the Saxifrage family has heavily "cut" foliage. It does best in rocky, moist areas, but is more drought-tolerant than other astilbes. Rosy lavender 8" spikes flower in August. Spreads rapidly by rhizomes, but easily controlled. Zones 3-8.

Astilbe simplicifolia [sim-pli-si-fo-lee-ah]. Perennial plant with white flower spikes in July-August. 8-10" tall. 'Rosea' is smaller with rich pink flowers. 'William Buchanan' has reddish leaves with cream flowers. Likes rich loam with moisture; does well in part or full shade. Japan. Zones 4-8.

Athyrium niponicum 'Pictum' [ah-thi-ree-um ni-pon-eh-kum pik-tum]. Japanese Painted Fern. Deciduous with fronds 8-12" long of a soft gray-green, whitish in the center with wine-red stems. The lovely colorings show best in partial shade. Moist, humus-rich soil. The fronds emerge in late May. Zones 5-8.

Aubrieta deltoides [oh-bree-ay-tah del-toe-i-dees]. Rockcress. A fairly easy, prostrate mat-forming perennial with pink or purple flowers, 6" high trailing to 2'. A classic rockery plant, it looks best dropping over a wall and often does best in an east-facing exposure. It should be pruned back after blooming to keep it compact and to avoid seeding. From stony, limy rockslides of the Mediterranean. Zones 4-8.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z