Zone 6 is the sweet spot of low-water gardening. Winter lows average −10°F to 0°F on the USDA Plant Hardiness Zone Map: cold enough that palms and most agaves are out, mild enough to keep plants zone 5 gardeners gamble on. On the 2023 map, zone 6 includes Denver, Boulder and most of Colorado Springs (6a), Santa Fe and Bend (6b), Logan, Park City, Flagstaff and Durango (6a), and Pocatello (6b). Albuquerque (7b), Boise (7a) and Salt Lake City (7b) are warmer than people assume, so check your ZIP before you shop.
Every plant below is rated to at least zone 6 and is low-water once established. The second half of the list is the zone 6 bonus set: plants that zone 5 usually loses.
The 24 at a glance
| Plant | Zones | Water | Height | Bloom / feature |
|---|---|---|---|---|
| Catmint 'Walker's Low' | 4–8 | Low | 24–30 in | Late spring–fall |
| Rocky Mountain penstemon | 4–9 | Very low | 24–30 in | Late spring |
| Blanket flower | 3–9 | Very low | 12–24 in | Summer–fall |
| Russian sage | 4–9 | Very low | 36–48 in | July–fall |
| Sunset hyssop (agastache) | 5–9 | Very low | 20–36 in | Midsummer–frost |
| English lavender | 5–9 | Low | 18–24 in | Early summer |
| Lavandin 'Phenomenal' | 5–9 | Low | 24–30 in | Summer |
| Blue grama | 3–10 | Very low | 12–24 in | Summer–winter |
| Little bluestem | 3–9 | Very low | 24–48 in | Fall–winter color |
| Karl Foerster feather reed grass | 4–9 | Low | 36–60 in | June–winter |
| Rabbitbrush | 4–9 | Very low | 2–5 ft | September |
| Apache plume | 4–8 | Very low | 4–6 ft | Late spring–fall |
| Blue mist spirea | 5–9 | Low | 2–3 ft | Late summer |
| Creeping thyme | 4–8 | Low | 1–3 in | Early summer |
| Claret cup cactus | 5–9 | Very low | 6–12 in | Spring |
| Zone 6 bonuses | ||||
| Autumn sage (Salvia greggii) | 6–9 | Low | 24–36 in | Spring–fall |
| Santolina | 6–9 | Low | 12–24 in | Early summer; silver foliage |
| Red hot poker | 5–9 (reliable in 6) | Low | 24–48 in | Early summer |
| Red yucca | 5–10 (reliable in 6) | Very low | 3–5 ft | Late spring–fall |
| Hardy ice plant | 5–9 (reliable in 6) | Very low | 3–6 in | June–September |
| Turquoise Tails blue sedum | 5–9 | Very low | 6–10 in | Summer |
| Parry's agave | 6–9* | Very low | 1.5–2 ft | Rarely |
| Chinese pistache | 6–9 | Low | 25–40 ft | Fall color |
| Chitalpa | 6–9 | Moderate | 20–35 ft | Summer |
*The Missouri Botanical Garden rates Parry's agave zones 7–10; zone 6 is realistic only in dry, well-drained sites.
The dependable core
These are hardy a zone or more colder, so they're rock-solid in zone 6.
Catmint (Nepeta × faassenii 'Walker's Low')
Zones 3–8 · Water Low · Size 24–30 in · Bloom Late spring to fall
The blue haze that anchors a zone 6 bed. Care tip: Shear catmint by a third after the first flush.
Rocky Mountain penstemon (Penstemon strictus)
Zones 4–9 · Water Very low · Size 24–30 in · Bloom Late spring
A native hummingbird magnet. Care tip: Gravel mulch around the crown of penstemon. See penstemon varieties for more species.
Blanket flower (Gaillardia aristata)
Zones 3–8 · Water Very low · Size 12–24 in · Bloom Summer to fall
Red-and-gold daisies all summer. Care tip: Let blanket flower reseed.
Russian sage (Salvia yangii)
Zones 4–9 · Water Very low · Size 36–48 in · Bloom July to fall
A silver-and-lavender cloud. Care tip: Cut Russian sage to 12 inches in early spring.
Sunset hyssop (Agastache rupestris)
Zones 4–10 · Water Very low · Size 20–36 in · Bloom Midsummer to frost
The zone 6 signature plant: iffy in wet zone 5 winters, dependable here. Plant Select rates it zones 4b–10. Care tip: Don't cut agastache back until spring.
English lavender and lavandin (Lavandula angustifolia, L. × intermedia 'Phenomenal')
Zones 5–9 · Water Low · Size 18–30 in · Bloom Summer
English lavender is easy in zone 6, and zone 6 also keeps the larger, showier lavandins more reliably. 'Phenomenal' is one of the hardiest. See growing lavender in a xeriscape. Care tip: Prune after bloom, never into bare wood.
Blue grama, little bluestem and Karl Foerster
Zones 3–10, 3–9 and 4–9 · Water Very low to low · Size 1–5 ft
Native texture from blue grama and little bluestem, plus the vertical accent of feather reed grass. More in ornamental grasses. Care tip: Leave all three standing until early spring.
Rabbitbrush, apache plume and blue mist spirea
Zones 4–9, 4–8 and 5–9 · Water Very low to low · Size 2–6 ft
The xeric structure set: fall gold from rabbitbrush, months of bloom and seed plumes from apache plume, and late-summer blue from spirea. More in drought-tolerant shrubs. Care tip: Cut blue mist spirea nearly to the ground each spring.
Creeping thyme (Thymus praecox)
Zones 4–8 · Water Low · Size 1–3 in · Bloom Early summer
A walkable mat for paths and patio joints. Care tip: Shear lightly after bloom. Compare options in the groundcover guide.
Claret cup cactus (Echinocereus triglochidiatus)
Zones 5–9 · Water Very low · Size 6–12 in · Bloom Spring, scarlet
Outrageous bloom on zero water. Care tip: Plant claret cup in a raised, gritty bed. More in cold-hardy cactus.
Zone 6 bonuses
Autumn sage (Salvia greggii)
Zones 6–9 · Water Low · Size 24–36 in · Bloom Spring to fall, red, pink, coral
A small, woody sage that blooms for months and feeds hummingbirds. The Missouri Botanical Garden rates it zones 6–9; Plant Select's hardier selections are rated to zone 5b. See the salvia guide. Care tip: Wait until new growth appears in spring before cutting out dead tips.
Santolina (Santolina chamaecyparissus)
Zones 6–9 · Water Low · Size 12–24 in · Bloom Early summer, yellow buttons
Silver, aromatic evergreen mounds for edging, rated zones 6–9. Care tip: Shear after bloom to keep it tight and prevent flopping.
Red hot poker (Kniphofia uvaria)
Zones 5–9 · Water Low · Size 24–48 in · Bloom Early summer
Rated to zone 5 but far more reliable in zone 6, where the crown doesn't sit frozen and wet. Care tip: Tie red hot poker leaves up over the crown in late fall.
Red yucca (Hesperaloe parviflora)
Zones 5–10 · Water Very low · Size 3–5 ft in bloom · Bloom Late spring to fall, coral
Coral bloom wands all summer; marginal in zone 5, dependable in zone 6. Care tip: Give red yucca reflected heat and remove spent stalks at the base.
Hardy ice plant and Turquoise Tails sedum
Zones 5–9 · Water Very low · Size 3–10 in
Hardy ice plant (Delosperma cooperi), rated zones 5–9 (the Missouri Botanical Garden says 6–10), is dependable here, and Plant Select's Turquoise Tails blue sedum adds year-round blue. Avoid the tender Wheels of Wonder and Jewels of the Desert series, which Plant Select treats as annuals. Care tip: Gravel mulch only.
Parry's agave (Agave parryi)
Zones 6–9 in dry sites (MBG: 7–10) · Water Very low · Size 1.5–2 ft
A true agave for zone 6 if you give it a raised, gravelly bed and no winter water. The Missouri Botanical Garden rates it zones 7–10, so expect occasional losses in wet winters. Havard agave (cold-hardy agave) follows the same rules. See cold-hardy agave and yucca. Care tip: Seek high-elevation forms such as var. couesii.
Chinese pistache (Pistacia chinensis)
Zones 6–9 · Water Low · Size 25–40 ft · Feature Orange-red fall color
A tough, low-water shade tree with brilliant fall color that zone 5 can't grow. Care tip: Water deeply for the first three years. More in low-water trees.
Chitalpa (× Chitalpa tashkentensis)
Zones 6–9 · Water Moderate · Size 20–35 ft · Bloom Summer, pink to white
The desert willow hybrid that brings orchid-like summer flowers to zone 6. It's thirstier than desert willow: the Missouri Botanical Garden lists medium water. Care tip: Give it a deep soak every couple of weeks in summer.
Zone 6 success rules
- Drainage still decides winters. Zone 6 cold snaps kill borderline plants through wet roots, not air temperature. Plant agave, lavender and agastache high and gritty (see xeriscape soil prep).
- Use microclimates for the bonuses. A south-facing wall is the place for autumn sage, santolina and agave.
- Beware false spring. Zone 6 springs lure plants out early, then freeze them. Don't push new growth with early fertilizer or water.
- Water new plantings through their first season, then taper. That holds in every zone.
From our installs
Most of Denver's metro sits in zone 6a on the 2023 map, and it's where most of our Front Range installs are. The zone 6 bonuses do well for us in hot, well-drained spots; autumn sage and santolina struggle in clay that stays wet in winter, so we raise those beds and use gravel mulch. New plantings get deep water once or twice a week the first summer, tapering in September. Hail shreds broad leaves most summers, which is one more reason we lean on fine-leaved and silver plants. (Xeris Landscaping is owned by Xeriscaping.com's founder.)
Frequently asked questions
Is Denver zone 5 or zone 6?
On the 2023 USDA map, central Denver is zone 6a. Higher suburbs such as Golden and parts of Douglas County are 5b. See the Denver zone page or the Denver xeriscaping guide.
What can I grow in zone 6 that I can't in zone 5?
Autumn sage, santolina, Chinese pistache, chitalpa, and (in dry sites) Parry's agave. Agastache, red hot poker, red yucca and hardy ice plant also become far more reliable.
Is Colorado Springs zone 5 or 6?
Mostly 6a, with northern and eastern areas such as Black Forest in 5b. See xeriscaping in Colorado Springs.
When should I plant in zone 6?
Spring after the last frost, or September to early October for most perennials, grasses and shrubs. Plant cactus and agave in late spring.
What if I'm in zone 5 or zone 7?
See xeriscape plants for zone 5 and the upcoming zone 7 guide. The hardiness zone guide explains how the zones work.
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