When to plant swiss chard in Idaho
Idaho’s average last spring frost is May 10, and the first fall frost typically arrives around September 25 — about 138 frost-free days (USDA zones 3b, 4b, 5b, 6a, 6b, 7a). Swiss Chard needs 50–60 days to mature, which fits comfortably within Idaho's growing season.
Idaho covers a wide range of climates, so your exact frost dates may differ from the state average by two weeks or more. For dates tuned to your town, use the calendar generator.
When to plant swiss chard in Idaho: the short answer
For a spring planting, plant out Apr 19 – May 6, with seeds started indoors Apr 5 – Apr 19. Seeds germinate in soil from 40 to 85°F.
Windows are ~1–2 week bands around each date. Frost dates are a statewide average from NOAA/NCEI normals; your town may differ by two weeks or more. Calendar year 2026.
How to grow swiss chard in Idaho, step by step
- Start seeds indoors (Apr 5 – Apr 19). Sow seeds 0.75 inch deep in seed-starting mix under bright light. They take 5-14 days to sprout, fastest in soil around 70°F. Harden seedlings off for a week before they go outside.
- Prepare the bed. It needs six or more hours of sun for the best growth, though four to six hours in partial shade is enough and loose soil at least 12 inches deep, with a pH between 6.0 and 7.5. Dig in compost before planting.
- Plant out (Apr 19 – May 6). Space plants about 9 inches apart in rows 18 inches apart. It tolerates a light frost but not a hard freeze. As a cool-season crop it does best before summer heat arrives in Idaho.
- Water and feed. Give it steady, even moisture, about an inch of water a week from rain or the hose.
- Watch for pests and problems. Pests: leaf miner, aphids, flea beetle. Diseases and disorders: cercospora leaf spot, downy mildew.
- Harvest (from about Jun 15 – Jun 25). Swiss Chard takes 50-60 days to reach harvest. One of the most heat-tolerant leafy greens - a single spring sowing usually carries through summer into fall if kept picked.
Figures come from our crop data; dates use Idaho’s average frost dates. More in the full swiss chard growing guide.
Swiss Chard planting dates by USDA zone in Idaho
Idaho spans USDA zones 3b, 4b, 5b, 6a, 6b, 7a. Colder zones, usually higher or further inland, have a later last spring frost and an earlier first fall frost than the state average, so the swiss chard dates shift with them.
| Zone | Last frost | First frost | Season | Start indoors | Plant swiss chard |
|---|---|---|---|---|---|
| Zone 3 | May 15 | Sep 15 | 120 days | Apr 10 – Apr 24 | Apr 24 – May 11 |
| Zone 4 | May 10 | Sep 25 | 135 days | Apr 5 – Apr 19 | Apr 19 – May 6 |
| Zone 5 | Apr 30 | Oct 5 | 160 days | Mar 26 – Apr 9 | Apr 9 – Apr 26 |
| Zone 6 | Apr 15 | Oct 15 | 185 days | Mar 11 – Mar 25 | Mar 25 – Apr 11 |
| Zone 7 | Apr 5 | Oct 25 | 200 days | Mar 1 – Mar 15 | Mar 15 – Apr 1 |
When to plant swiss chard in nearby states
Questions gardeners in Idaho ask
When is the best time to plant swiss chard in Idaho?
Plant swiss chard transplants outdoors in Idaho between April 19 and May 6. That timing is set by Idaho's average last spring frost of May 10; Idaho spans several climates, so cooler and higher parts of the state run later.
When should I start swiss chard seeds indoors in Idaho?
Start seeds indoors between April 5 and April 19, about 4 weeks before the last frost, so the seedlings are ready to plant out from April 19.
Can I plant swiss chard in the fall in Idaho?
Yes. For a fall crop, sow between July 7 and July 24, so the crop matures in cool weather before Idaho's first frost around September 25.
When will swiss chard planted in Idaho be ready to harvest?
Planted on time, swiss chard is usually ready from about June 15 to June 25, 50-60 days after planting.
When is the last frost in Idaho?
On average around May 10, with the first fall frost around September 25 - about 138 frost-free days. Your town may differ by two weeks or more.