Gardening in Idaho Falls, ID
This metro spans USDA zones 4b to 6a, so there is no single zone for Idaho Falls, ID and anyone who gives you one is rounding. 40% of its ZIP codes are zone 5a; the rest are not.
Which zone you are in depends where you are
Idaho Falls, ID covers 4 hardiness zones. A guide that gives the metro one zone has picked whichever is largest and rounded everyone else into it — which is fine for the 40% in zone 5a and wrong for the other 60%. Here is the actual split.
| Zone | ZIP codes | Share | |
|---|---|---|---|
| 5a | 8 | 40% | |
| 5b | 8 | 40% | |
| 4b | 2 | 10% | |
| 6a | 2 | 10% |
Zones are published per ZIP code, so yours is exact even though the metro's is not. The hardiness tool will tell you which one you are in.
Your freeze dates
Those are the earliest and latest medians among the 11 stations serving this metro — not an average, and not one station standing in for the rest. Half of years freeze later than a station's own median.
The spread is the point. Even in a metro that is one hardiness zone throughout, its stations disagree about the last spring freeze. Hardiness zone and frost date measure different things — a zone is the average annual coldest night, a freeze date is when the season turns — and a place can be uniform in one and varied in the other. Use the tools below with your own ZIP rather than the ends of this range.
Your growing season
NOAA publishes a growing-season length for each station, and across the 11 stations serving Idaho Falls, ID it runs 71–148 days . That figure is published, not computed from the two freeze dates — subtracting one from the other gives the wrong answer wherever a season crosses New Year. Mean summer high (June–August) runs 77–85 °F , below the 90 °F point where cool-season crops reliably bolt.
When to start seeds in Idaho Falls, ID
Every spring job for 63 crop dates, counted from this metro's own last spring freeze. Each is a range across all 11 stations — the earliest and latest that job falls anywhere in the metro — because no one station speaks for the whole area.
| Crop | Job | When | Offset |
|---|---|---|---|
| Green Onions | Start indoors | March 14 – April 25 | 8 weeks before |
| Peppers | Start indoors | March 14 – April 25 | 8 weeks before |
| Broccoli | Start indoors | March 28 – May 9 | 6 weeks before |
| Cabbage | Start indoors | March 28 – May 9 | 6 weeks before |
| Collards | Start indoors | March 28 – May 9 | 6 weeks before |
| Kale | Start indoors | March 28 – May 9 | 6 weeks before |
| Leaf Lettuce | Start indoors | March 28 – May 9 | 6 weeks before |
| Peas | Direct sow | March 28 – May 9 | 6 weeks before |
| Spinach | Direct sow | March 28 – May 9 | 6 weeks before |
| Sweet Potato | Start indoors | March 28 – May 9 | 6 weeks before |
| Tomatoes | Start indoors | March 28 – May 9 | 6 weeks before |
| Bok Choy | Start indoors | April 4 – May 16 | 5 weeks before |
| Kohlrabi | Start indoors | April 4 – May 16 | 5 weeks before |
| Swiss Chard | Start indoors | April 4 – May 16 | 5 weeks before |
| Arugula | Direct sow | April 11 – May 23 | 4 weeks before |
| Baby Salad Greens | Direct sow | April 11 – May 23 | 4 weeks before |
| Beets | Direct sow | April 11 – May 23 | 4 weeks before |
| Green Onions | Direct sow | April 11 – May 23 | 4 weeks before |
| Mustard Greens | Direct sow | April 11 – May 23 | 4 weeks before |
| Okra | Start indoors | April 11 – May 23 | 4 weeks before |
| Radishes | Direct sow | April 11 – May 23 | 4 weeks before |
| Turnips | Direct sow | April 11 – May 23 | 4 weeks before |
| Cabbage | Set out | April 18 – May 30 | 3 weeks before |
| Carrots | Direct sow | April 18 – May 30 | 3 weeks before |
| Collards | Direct sow | April 18 – May 30 | 3 weeks before |
| Collards | Set out | April 18 – May 30 | 3 weeks before |
| Cucumbers | Start indoors | April 18 – May 30 | 3 weeks before |
| Green Onions | Set out | April 18 – May 30 | 3 weeks before |
| Kale | Direct sow | April 18 – May 30 | 3 weeks before |
| Kale | Set out | April 18 – May 30 | 3 weeks before |
| Kohlrabi | Direct sow | April 18 – May 30 | 3 weeks before |
| Kohlrabi | Set out | April 18 – May 30 | 3 weeks before |
| Leaf Lettuce | Direct sow | April 18 – May 30 | 3 weeks before |
| Pumpkins | Start indoors | April 18 – May 30 | 3 weeks before |
| Summer Squash | Start indoors | April 18 – May 30 | 3 weeks before |
| Winter Squash | Start indoors | April 18 – May 30 | 3 weeks before |
| Zucchini | Start indoors | April 18 – May 30 | 3 weeks before |
| Bok Choy | Direct sow | April 25 – June 6 | 2 weeks before |
| Bok Choy | Set out | April 25 – June 6 | 2 weeks before |
| Broccoli | Set out | April 25 – June 6 | 2 weeks before |
| Cilantro | Direct sow | April 25 – June 6 | 2 weeks before |
| Leaf Lettuce | Set out | April 25 – June 6 | 2 weeks before |
| Swiss Chard | Direct sow | April 25 – June 6 | 2 weeks before |
| Swiss Chard | Set out | April 25 – June 6 | 2 weeks before |
| Dill | Direct sow | May 2 – June 13 | 1 week before |
| Bush Beans | Direct sow | May 16 – June 27 | 1 week after |
| Cucumbers | Set out | May 16 – June 27 | 1 week after |
| Pumpkins | Direct sow | May 16 – June 27 | 1 week after |
| Pumpkins | Set out | May 16 – June 27 | 1 week after |
| Summer Squash | Direct sow | May 16 – June 27 | 1 week after |
| Summer Squash | Set out | May 16 – June 27 | 1 week after |
| Sweet Corn | Direct sow | May 16 – June 27 | 1 week after |
| Tomatoes | Set out | May 16 – June 27 | 1 week after |
| Winter Squash | Direct sow | May 16 – June 27 | 1 week after |
| Winter Squash | Set out | May 16 – June 27 | 1 week after |
| Zucchini | Direct sow | May 16 – June 27 | 1 week after |
| Zucchini | Set out | May 16 – June 27 | 1 week after |
| Cucumbers | Direct sow | May 23 – July 4 | 2 weeks after |
| Okra | Direct sow | May 23 – July 4 | 2 weeks after |
| Okra | Set out | May 23 – July 4 | 2 weeks after |
| Peppers | Set out | May 23 – July 4 | 2 weeks after |
| Southern Peas | Direct sow | May 23 – July 4 | 2 weeks after |
| Sweet Potato | Set out | May 23 – July 4 | 2 weeks after |
The week offsets are conventional extension guidance and vary by variety; the freeze dates they are counted from are measured. For a single date rather than a range, run when do I start my seeds? with your own ZIP code.
What survives the winter changes across Idaho Falls, ID
Of 74 perennial fruits, nuts, berries, vegetables and herbs, 51 come through the winter in zone 6a and only 34 in zone 4b. That is a different garden at each end of the same metro.
| Zone | ZIPs | Survive | Fail for being too warm |
|---|---|---|---|
| 4b | 2 | 34 of 74 | 0 |
| 5a | 8 | 48 of 74 | 0 |
| 5b | 8 | 48 of 74 | 0 |
| 6a | 2 | 51 of 74 | 0 |
The last column is the counterintuitive one, and it is why the totals do not simply rise as the winters get milder. Most temperate fruit needs a documented number of hours below about 45 °F to break dormancy and set a crop, so an apple fails in a winter that is too warm; currants and rhubarb cook in the summer heat that comes with it. See the full list with reasons.
The 11 stations behind these numbers
Every figure above comes from these, and each is named so you can check it. Distances vary by ZIP code, so the tools report yours rather than this page guessing.
| Station | NOAA ID | Last spring freeze | First fall freeze | Season |
|---|---|---|---|---|
| Afton, WY | USC00480027 | June 20 | September 1 | 71 days |
| Arco 17 SW, ID | USW00004126 | May 24 | October 1 | 130 days |
| Arco, ID | USC00100375 | May 22 | September 22 | 119 days |
| Driggs, ID | USC00102676 | June 13 | September 9 | 86 days |
| Hamer 4 NW, ID | USC00103964 | June 3 | September 11 | 98 days |
| Howe, ID | USC00104384 | May 24 | September 14 | 113 days |
| Idaho Falls - Kifi, ID | USC00104455 | May 9 | October 1 | 142 days |
| Idaho Falls 16 SE, ID | USC00104456 | June 9 | September 11 | 93 days |
| Idaho Falls Fanning FLD, ID | USW00024145 | May 23 | September 20 | 114 days |
| Monteview, ID | USC00106080 | June 12 | September 7 | 87 days |
| Rigby, ID | USC00107689 | May 9 | October 5 | 148 days |
These are medians, not averages — NOAA publishes freeze dates as a probability distribution, and half of years freeze later than the date shown.
Work out your own dates
Each of these takes a ZIP code and answers for that ZIP alone, citing the station it used and how far away it is. There is a ZIP box in the header of every page.
- What survives my winter?
Runs on the hardiness zone, so it answers for all of Idaho Falls, ID at once — zone across 74 perennial fruits, berries, vegetables and herbs.
- When do I start my seeds?
Dates every spring job from your own last freeze — sow indoors, set out, direct sow.
- When do I sow the next round?
How often each crop is worth re-sowing, and when the next sowing is due.
- What can I still plant?
Counts the growing days left before your first fall freeze, crop by crop.
Where these numbers come from
The hardiness zone is the USDA 2023 Plant Hardiness Zone Map, published per ZIP code by PRISM at Oregon State. The freeze dates are NOAA's 1991–2020 Climate Normals, read from every station whose normals cover a ZIP code in this metro. Nothing here is estimated, and no station stands in for another.
This page names no single station on purpose. Picking one to represent a metro sounds reasonable and is not: the station serving the most ZIP codes is an artifact of where ZIP centroids happen to fall, and it selects a lock on the Monongahela for Pittsburgh and a far southern suburb for Chicago. A range across every station is true; a single cited date for a whole metro is not.