Colorado’s growing conditions run from the high plains around Denver to alpine valleys where summer barely gets going. Out of the 65 trees, shrubs, and perennials this site tracks, none fail across the entire state, but 36 fail somewhere in it. The real question isn’t whether a plant survives Colorado. It’s whether it survives your part of it.
What Will Not Survive a winter in Colorado
Colorado’s USDA hardiness range runs from 3b to 7b. That’s one of the widest spans covered on this site, stretching from mountain valleys cold enough to kill most ornamental shrubs outright to lower-elevation pockets near the state’s southeastern and western edges that barely dip below zero in a typical winter. The USDA Plant Hardiness Zone Map builds this range from a single number: the average annual extreme minimum temperature, drawn from the 1991-2020 climate normals. It says nothing about summer heat, soil, or rainfall. It only tells you how cold the coldest night tends to get.
Given that range, here’s the plain result: of the 65 landscape plants documented on this site, zero fail across the whole of Colorado. None of them are simply wrong for this state, full stop. That’s a different situation from a place like Alaska or Florida, where the local hardiness range sits so far to one extreme that certain plants can’t survive anywhere within the state’s borders.
That doesn’t mean every plant on the list is a safe bet wherever you garden in Colorado. It means the failures here are partial, not total, and they depend entirely on which end of that 3b-to-7b range your address falls into. A plant can be perfectly hardy on paper and still struggle here, because the warm end of a hardiness range is usually a heat limit rather than a cold one. A shrub rated hardy through zone 7b can still sulk through a dry, sun-blasted Colorado summer at elevation, even though it would never freeze out in winter. Hardy means it survives. It doesn’t promise the plant will thrive or even look particularly happy doing it.
So the useful work in Colorado isn’t screening out plants that can’t grow here at all. It’s figuring out which of the 36 partial-match plants apply to your specific zone, and that’s where the next section does the real work.
The plants that work in part of the state and not the rest
This is the section that actually matters for a state-level page, because Colorado’s zone range is wide enough that a single yes-or-no verdict would mislead close to half the readers. Of the 65 documented plants, 36 are hardy in part of the state’s 3b-7b range and not the rest. The pattern in the data is lopsided: the overwhelming majority fail at the cold end, not the warm one.
Plants that fail in the coldest zones
Most of the 36 partial plants drop out somewhere between zone 3b and zone 6b, meaning they’re excluded from the coldest parts of Colorado’s range but hold up fine at the lower elevations and warmer valleys. The table below lists them by which zones they’re missing.
| Plant | Type | Not hardy in |
|---|---|---|
| Ficus carica | fruit | 3b, 4a, 4b, 5a, 5b, 6a, 6b |
| Hydrangea macrophylla | shrub | 3b, 4a, 4b, 5a, 5b |
| Lagerstroemia indica | tree | 3b, 4a, 4b, 5a, 5b |
| Magnolia grandiflora | tree | 3b, 4a, 4b, 5a, 5b |
| Asimina triloba | fruit | 3b, 4a, 4b |
| Fragaria virginiana | fruit | 3b, 4a, 4b |
| Fragaria x ananassa | fruit | 3b, 4a, 4b |
| Prunus persica | fruit | 3b, 4a, 4b |
| Amsonia hubrichtii | perennial | 3b, 4a, 4b |
| Lavandula angustifolia | perennial | 3b, 4a, 4b |
| Buxus sempervirens | shrub | 3b, 4a, 4b |
| Fothergilla gardenii | shrub | 3b, 4a, 4b |
| Itea virginica | shrub | 3b, 4a, 4b |
| Cornus florida | tree | 3b, 4a, 4b |
| Liquidambar styraciflua | tree | 3b, 4a, 4b |
| Diospyros virginiana | fruit | 3b |
| Morus rubra | fruit | 3b |
| Prunus domestica | fruit | 3b |
| Pyrus communis | fruit | 3b |
| Rubus idaeus | fruit | 3b |
| Rubus occidentalis | fruit | 3b |
| Sambucus canadensis | fruit | 3b |
| Heuchera americana | perennial | 3b |
| Monarda didyma | perennial | 3b |
| Phlox paniculata | perennial | 3b |
| Salvia nemorosa | perennial | 3b |
| Hylotelephium spectabile | perennial | 3b |
| Ilex glabra | shrub | 3b |
| Kalmia latifolia | shrub | 3b |
| Betula nigra | tree | 3b |
| Cercis canadensis | tree | 3b |
| Nyssa sylvatica | tree | 3b |
| Platanus occidentalis | tree | 3b |
| Quercus rubra | tree | 3b |
Plants that fail at the warm end, or both ends
Only one plant on the list drops out at the warm end instead: Syringa vulgaris, which isn’t hardy in zone 7b, the mildest slice of Colorado’s range. One more, Weigela florida, fails at both extremes, missing 3b along with 7a and 7b, which leaves it working only in the state’s middle zones.
Finding out which of these zones is yours takes a county-level look, not a statewide one. The insulation page for Colorado on this site carries that county-by-county zone picture, and it’s the fastest way to confirm whether your address sits in the 3b-4b range where most of this list drops out, or further into the 6a-7b end where nearly all of it holds.
The soil and the summer they will be planted into
Colorado’s representative state soil is the Seitz series, an Alfisol classified as a forest soil of moderate fertility. Surface texture runs loam to silt, with 42 percent sand, 21 percent clay, and 37 percent silt, and it’s recorded as well drained. For a woody plant, drainage is the detail that matters most. Winter wet kills more perennials and shrubs than winter cold does, because saturated soil around dormant roots freezes and thaws repeatedly, and that cycle does more damage than a straight cold snap. A well-drained loam-to-silt profile like the Seitz series gives roots room to breathe through that cycle, which is a point in its favor for most of the 29 plants that are hardy across Colorado’s whole range.
Surface pH on the Seitz series runs about 5.6, slightly acid. That’s a soil-survey figure for the surface horizon of this series as mapped, not a number to apply to a home garden bed without checking. Organic matter is recorded around 70 percent, a figure that reflects a natural surface layer rather than a cultivated one; a worked garden bed won’t carry anything close to that once it’s been dug over and planted. None of these numbers replace a soil test on the actual planting site, since river bottoms, foothill slopes, and any lot a builder has graded or filled will differ from the mapped series.
Summer rainfall at the reference station comes to about 5.7 inches across June, July, and August, out of 14.5 inches for the year. August is the driest of the three months at 1.58 inches, with June at 1.94 and July at 2.14. That’s not a humidity reading and it’s not an irrigation schedule. It’s precipitation that has to be read against the soil it’s falling on. The same 1.58 inches in August behaves differently depending on where it lands: on the sandier end of the Seitz series texture it moves through the profile within a day, while a heavier clay pocket elsewhere in the state holds that same rain for a week. A rain gauge on the actual planting site, checked against how fast the ground drains after a storm, tells a gardener more than the summer total ever will on its own.
When to plant, here
At the reference station, the last spring frost falls between May 1 and May 11, and the first fall frost arrives between September 30 and October 12. Both are averages built from 1991-2020 freeze-probability data, not a guarantee for any single year, and they describe conditions at that one station. Denver sits at 5,280 feet on the plains; mountain towns run shorter seasons by a wide margin and can see frost even in July, while the western slope runs on its own separate schedule again.
Those two windows exist because a woody plant needs time to build roots before it’s asked to do anything else. A tree or shrub put in the ground too late in spring has to grow roots and push out leaves at the same time, right as the heat of a Colorado summer arrives. One planted too late in fall runs out of the mild weeks it needs to get established before the ground locks up for winter.
| Window | Best suited for | Main risk |
|---|---|---|
| Spring (after last frost, roughly May 1-11) | Most trees, shrubs, and perennials; gives a full growing season to establish before winter | A late freeze after an early warm spell can still catch new growth off guard |
| Autumn (before first frost, roughly Sept. 30-Oct. 12) | Many trees and shrubs, since cooler air and still-warm soil favor root growth without heat stress | Less time to establish roots before dormancy, especially at the cold end of the state’s range |
In the coldest slice of Colorado’s zone range, that autumn window shrinks further, since the first frost date arrives close on the heels of whatever planting gets done. And whichever window is chosen, a newly planted specimen needs regular water through its first season regardless of what its drought tolerance rating says. Those ratings describe plants that are already established, with root systems reaching well beyond the original planting hole. A first-year plant hasn’t built that yet.
Where to read about each one
Among the 29 plants documented on this site that are hardy across all of Colorado’s 3b-to-7b range, the trees include Acer rubrum, Acer saccharum, Amelanchier canadensis, Carpinus caroliniana, Ginkgo biloba, Juniperus virginiana, Picea abies, Pinus strobus, Quercus alba, Thuja occidentalis, and Tilia americana.
The shrubs on that same statewide list are Aronia arbutifolia, Clethra alnifolia, Hydrangea paniculata, Ilex verticillata, Physocarpus opulifolius, Spiraea japonica, and Viburnum dentatum.
And the perennials are Achillea millefolium, Asclepias tuberosa, Baptisia australis, Anacis verticillata, Echinacea purpurea, Iris sibirica, and Rudbeckia fulgida.
That leaves the 36 partial-match plants from earlier, which are worth a look too if a reader’s zone falls outside the sections where they drop out. All of these hardiness ranges come from the North Carolina Extension Gardener Plant Toolbox, a university extension plant database, and this page is what crosses those ranges against Colorado’s own 3b-7b hardiness picture. It’s worth keeping these figures separate from the apple variety adaptation zones held elsewhere on this site. Those come from a fruit-variety table and describe something different: how a specific apple cultivar performs, not whether a species survives a given winter low.