These unthirsty succulents, flowers, and grasses will thrive with little care - even on a roof.
1. Echinocactus grusoni
Golden spines cover this slow-growing native Mexican cactus that reaches 4 feet tall and 2½ feet wide. Small yellow flowers top the plant in summer. Sunset climate zones 12-24.
2. Lewisia cotyledon 'Sunset Strain'
This bloomer, from California and Oregon, has evergreen foliage and reaches a foot high and 10 inches wide. It's great in rock gardens, but needs excellent drainage. Zones 1-7 and 14-17.
3. Nassella tenuissima
Wispy green blades form clumps reaching 2 feet tall and wide. This grass found in Texas, New Mexico, and Mexico develops blond summer flower heads. Zones 2b-24.
4. Sedum spathulifolium 'Cape Blanco'
Tiny blue-green leaves form tight rosettes on trailing stems. This low grower from California makes a great groundcover. Zones 2-9 and 14-24.
5. Lavandula multifida
Felty silver foliage covers these Mediterranean shrubs reaching 3 feet wide and half as tall. Thin stems topped with violet blooms appear from spring into fall. Zones 16-24.
6. Libertia peregrinans
Thin, stiff orangey blades of this iris relation from New Zealand reach 2 feet tall and half as wide. Clusters of inch-wide white flowers bloom in spring and summer. Zones 8, 9, and 14-24.
7. Sedum rupestre 'Angelina'
Short chartreuse leaves grow on stems up to 6 inches tall. This succulent from Europe spreads freely, making it a fluffy groundcover or filler between other plants. Zones 2-24.
8. Sedum spurium 'Voodoo'
Small, rounded burgundy leaves cover this low-growing, quick-spreading succulent from the Caucasus. Tiny reddish flowers bloom in summer. Zones 1-10 and 14-24.
9. Salvia clevelandii
Purple-blue flower spikes rise above aromatic gray-green foliage in early summer. This sage, from Southern California and northern Baja, grows 3 to 5 feet tall, and 5 to 8 feet wide. Zones 8, 9, and 12-24.
This European native, with gray-green, pink-tipped rosettes from 2 to 5 inches across, grows into clumps spanning 2 feet or more. Reddish flowers shoot from thin, 2-foot-tall stems. Zones 2-24.
11. Agastache rugosa
Stems of glossy green, licorice-scented leaves reach 5 feet tall and 2 feet wide. This perennial from Korea has purple-blue summer flowers that hummingbirds love. Zones 4-24.
12. Helictotrichon sempervirens
Thin, blue-gray blades of this Mediterranean grass grow in clumps that reach 2 to 3 feet tall and wide. Blond flower clusters form 2 feet above foliage in spring. Zones 1-12 and 14-24.