Can I Grow Ornamental Kale in Washington?

Ornamental Kale in Washington — the short answer

Washington is not one climate

Where in Washington Fits Best

Even within Washington's zones 4a-9b, county microclimates differ enough to change what thrives. These counties carry the closest zone match for ornamental kale (USDA PHZM 2023):

Zone Comparison

Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS, and university Extension sources — per-field provenance varies and is published with the dataset. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.

When to Plant Ornamental Kale in Washington

Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: Growable Ground Plant Database — frost-free days from FAO ECOCROP, days to harvest from university Extension production guides, and growing-degree-day and chill-hour minimums that are compilation estimates rather than published figures. Your site's own frost dates can run earlier or later than the state range — a parcel report pins them down.

Growing Season Fit

Ornamental Kale is grown in zones 2–10, which covers every zone Washington contains (4a-9b). We have no sourced winter-survival figure for ornamental kale, so this page does not say whether it overwinters here. Washington's typical season runs ~208 frost-free days against the ~60 ornamental kale needs.

GDD and chill-hour figures are computed from PRISM 1991-2020 monthly climate normals; frost-free days from NOAA Regional Climate Centers ACIS, 1991-2020. Each is the state median across its counties (P25/P75 span the within-state spread). Hardiness-zone range is USDA PHZM 2023.

Soil + Drainage Fit

Ornamental Kale tolerates a wide pH range (pH 5.5-8.5) — 3 units, acid ground through alkaline — so soil acidity is rarely what limits it in Washington. A soil test is still worth having, but for what else it tells you about this site, not to clear this plant. It will grow across that whole span, but it does best between pH 6 and 7 — worth knowing before you decide whether a Washington soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Washington site is heavier clay or sits in a low spot, a raised bed lifts the roots above wet ground, or work in compost. pH range, preferred pH and drainage need: We haven't confirmed this against a published source yet.

Plant pH requirements: FAO ECOCROP and USDA PLANTS, with the remaining rows from other published sources or Growable Ground compilation. Drainage: FAO ECOCROP, with the remaining rows from other published sources or Growable Ground compilation. Washington soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.

What Else to Consider for Ornamental Kale in Washington

The zone range tells you where ornamental kale is grown — but Washington growers also need to think about:

What to actually do about these — and the constraints that apply to every Washington grower, not just ornamental kale — is covered on the Washington growing guide.

Where in Washington Ornamental Kale Is Zone-Hardy

Ornamental Kale is rated for USDA zones 2–10. Every one of Washington’s 39 counties sits inside that band — from Ferry County at zone 6a to San Juan County at zone 9a — so winter cold is not what decides this plant anywhere in the state. What is left to vary is your own parcel: slope, shelter and cold-air drainage routinely move a site half a zone either way from the county figure.

Across those 39 counties Washington’s winter-low ladder runs from zone 6a in Ferry County to zone 9a in San Juan County — 3 USDA zones of spread, which is 30°F between the two counties’ average coldest night of the year. That is why a statewide hardiness answer is where you start and not where you finish.

The planting window moves with it. Whatcom County holds its last hard freeze (28°F) until about May 29, while Island County is clear by Feb 8 — 110 days apart. Set ornamental kale out on your county’s date, not the state’s.

County hardiness zones: USDA Plant Hardiness Zone Map (PHZM) 2023, per county. County last-freeze dates: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F killing freeze — earlier than the folk 32°F "last frost". Ornamental Kale’s zone 2–10 band: Not verified. A parcel report resolves your address’s own zone and frost dates rather than its county’s.

Pollinator + Wildlife Value

Ornamental Kale draws honeybees and native bees (moderate value). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, ornamental kale can only work that bloom inside Washington's frost window — roughly 208 days, opening after the last 28°F freeze (Mar 16 - Apr 15) and closing at the first (Oct 24 - Nov 18), per NOAA Regional Climate Centers ACIS, 1991-2020. Pollinator value: We haven't confirmed this against a published source yet.

Washington Cooperative Extension

For Washington-specific cultivar recommendations, planting calendars, and pest pressure for ornamental kale, the canonical source is WSU Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.

Is Ornamental Kale native to Washington?

No — the USDA PLANTS Database lists Ornamental Kale as introduced rather than native in the Lower 48, so it is not part of Washington's native flora. It grows here as a garden plant; pairing it with a few Washington natives keeps local pollinators fed too.

Looking for plants that belong here? The Washington growing guide lists plants that USDA PLANTS records growing in Washington and that Kew and NatureServe Explorer both list in its native range, leaving out any that NatureServe flags as exotic there or that our audit holds.

State records: USDA PLANTS Database state-distribution data (presence, not state-level nativity), accessed 2026-10-19.

Common Questions About Growing Ornamental Kale in Washington