Gardening in Boise City, ID
This metro spans USDA zones 6a to 7a, so there is no single zone for Boise City, ID and anyone who gives you one is rounding. 90% of its ZIP codes are zone 7a; the rest are not.
Which zone you are in depends where you are
Boise City, ID covers 3 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 90% in zone 7a and wrong for the other 10%. Here is the actual split.
| Zone | ZIP codes | Share | |
|---|---|---|---|
| 7a | 38 | 90% | |
| 6b | 3 | 7% | |
| 6a | 1 | 2% |
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 18 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 18 stations serving Boise City, ID it runs 80–181 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 77–95 °F , at or above the 90 °F point where cool-season crops bolt and tomato and pepper pollen fails — so midsummer sowings of lettuce and its relatives are worth holding here.
When to start seeds in Boise City, ID
Every spring job for 63 crop dates, counted from this metro's own last spring freeze. Each is a range across all 18 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 | February 20 – April 22 | 8 weeks before |
| Peppers | Start indoors | February 20 – April 22 | 8 weeks before |
| Broccoli | Start indoors | March 6 – May 6 | 6 weeks before |
| Cabbage | Start indoors | March 6 – May 6 | 6 weeks before |
| Collards | Start indoors | March 6 – May 6 | 6 weeks before |
| Kale | Start indoors | March 6 – May 6 | 6 weeks before |
| Leaf Lettuce | Start indoors | March 6 – May 6 | 6 weeks before |
| Peas | Direct sow | March 6 – May 6 | 6 weeks before |
| Spinach | Direct sow | March 6 – May 6 | 6 weeks before |
| Sweet Potato | Start indoors | March 6 – May 6 | 6 weeks before |
| Tomatoes | Start indoors | March 6 – May 6 | 6 weeks before |
| Bok Choy | Start indoors | March 13 – May 13 | 5 weeks before |
| Kohlrabi | Start indoors | March 13 – May 13 | 5 weeks before |
| Swiss Chard | Start indoors | March 13 – May 13 | 5 weeks before |
| Arugula | Direct sow | March 20 – May 20 | 4 weeks before |
| Baby Salad Greens | Direct sow | March 20 – May 20 | 4 weeks before |
| Beets | Direct sow | March 20 – May 20 | 4 weeks before |
| Green Onions | Direct sow | March 20 – May 20 | 4 weeks before |
| Mustard Greens | Direct sow | March 20 – May 20 | 4 weeks before |
| Okra | Start indoors | March 20 – May 20 | 4 weeks before |
| Radishes | Direct sow | March 20 – May 20 | 4 weeks before |
| Turnips | Direct sow | March 20 – May 20 | 4 weeks before |
| Cabbage | Set out | March 27 – May 27 | 3 weeks before |
| Carrots | Direct sow | March 27 – May 27 | 3 weeks before |
| Collards | Direct sow | March 27 – May 27 | 3 weeks before |
| Collards | Set out | March 27 – May 27 | 3 weeks before |
| Cucumbers | Start indoors | March 27 – May 27 | 3 weeks before |
| Green Onions | Set out | March 27 – May 27 | 3 weeks before |
| Kale | Direct sow | March 27 – May 27 | 3 weeks before |
| Kale | Set out | March 27 – May 27 | 3 weeks before |
| Kohlrabi | Direct sow | March 27 – May 27 | 3 weeks before |
| Kohlrabi | Set out | March 27 – May 27 | 3 weeks before |
| Leaf Lettuce | Direct sow | March 27 – May 27 | 3 weeks before |
| Pumpkins | Start indoors | March 27 – May 27 | 3 weeks before |
| Summer Squash | Start indoors | March 27 – May 27 | 3 weeks before |
| Winter Squash | Start indoors | March 27 – May 27 | 3 weeks before |
| Zucchini | Start indoors | March 27 – May 27 | 3 weeks before |
| Bok Choy | Direct sow | April 3 – June 3 | 2 weeks before |
| Bok Choy | Set out | April 3 – June 3 | 2 weeks before |
| Broccoli | Set out | April 3 – June 3 | 2 weeks before |
| Cilantro | Direct sow | April 3 – June 3 | 2 weeks before |
| Leaf Lettuce | Set out | April 3 – June 3 | 2 weeks before |
| Swiss Chard | Direct sow | April 3 – June 3 | 2 weeks before |
| Swiss Chard | Set out | April 3 – June 3 | 2 weeks before |
| Dill | Direct sow | April 10 – June 10 | 1 week before |
| Bush Beans | Direct sow | April 24 – June 24 | 1 week after |
| Cucumbers | Set out | April 24 – June 24 | 1 week after |
| Pumpkins | Direct sow | April 24 – June 24 | 1 week after |
| Pumpkins | Set out | April 24 – June 24 | 1 week after |
| Summer Squash | Direct sow | April 24 – June 24 | 1 week after |
| Summer Squash | Set out | April 24 – June 24 | 1 week after |
| Sweet Corn | Direct sow | April 24 – June 24 | 1 week after |
| Tomatoes | Set out | April 24 – June 24 | 1 week after |
| Winter Squash | Direct sow | April 24 – June 24 | 1 week after |
| Winter Squash | Set out | April 24 – June 24 | 1 week after |
| Zucchini | Direct sow | April 24 – June 24 | 1 week after |
| Zucchini | Set out | April 24 – June 24 | 1 week after |
| Cucumbers | Direct sow | May 1 – July 1 | 2 weeks after |
| Okra | Direct sow | May 1 – July 1 | 2 weeks after |
| Okra | Set out | May 1 – July 1 | 2 weeks after |
| Peppers | Set out | May 1 – July 1 | 2 weeks after |
| Southern Peas | Direct sow | May 1 – July 1 | 2 weeks after |
| Sweet Potato | Set out | May 1 – July 1 | 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 Boise City, ID
Of 74 perennial fruits, nuts, berries, vegetables and herbs, 58 come through the winter in zone 7a and only 51 in zone 6a. That is a different garden at each end of the same metro.
| Zone | ZIPs | Survive | Fail for being too warm |
|---|---|---|---|
| 6a | 1 | 51 of 74 | 0 |
| 6b | 3 | 51 of 74 | 0 |
| 7a | 38 | 58 of 74 | 1 |
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 18 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 |
|---|---|---|---|---|
| Boise 7 N, ID | USC00101017 | May 17 | October 12 | 147 days |
| Boise Air Terminal, ID | USW00024131 | April 24 | October 21 | 179 days |
| Boise Lucky Peak Dam, ID | USC00101018 | April 30 | October 22 | 173 days |
| Bruneau, ID | USC00101195 | April 17 | October 17 | 181 days |
| Deer Flat Dam, ID | USC00102444 | April 23 | October 18 | 178 days |
| Emmett 2 E, ID | USC00102942 | April 30 | October 17 | 168 days |
| Garden Valley, ID | USC00103448 | June 1 | September 10 | 102 days |
| Glenns Ferry, ID | USC00103631 | May 1 | October 3 | 154 days |
| Grand View 4 NW, ID | USC00103760 | April 28 | October 6 | 162 days |
| Homedale 1 SE, ID | USC00104318 | April 24 | October 9 | 169 days |
| Idaho City, ID | USC00104442 | June 17 | September 5 | 80 days |
| Lowman, ID | USC00105414 | June 6 | September 4 | 87 days |
| Nampa Sugar Factory, ID | USC00106305 | April 29 | October 13 | 164 days |
| Ola, ID | USC00106586 | May 31 | September 16 | 108 days |
| Parma Exp Stn, ID | USC00106844 | April 27 | October 9 | 165 days |
| Reynolds, ID | USC00107648 | May 21 | September 28 | 126 days |
| Rockville 5 N, OR | USC00357277 | May 29 | September 14 | 108 days |
| Silver City 5 W, ID | USC00108412 | May 31 | October 6 | 128 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 Boise City, 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.