Gardening in Flagstaff, AZ
This metro spans USDA zones 5b to 7b, so there is no single zone for Flagstaff, AZ and anyone who gives you one is rounding. 44% of its ZIP codes are zone 7a; the rest are not.
Which zone you are in depends where you are
Flagstaff, AZ covers 5 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 44% in zone 7a and wrong for the other 56%. Here is the actual split.
| Zone | ZIP codes | Share | |
|---|---|---|---|
| 7a | 11 | 44% | |
| 6b | 6 | 24% | |
| 7b | 5 | 20% | |
| 6a | 2 | 8% | |
| 5b | 1 | 4% |
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 19 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 19 stations serving Flagstaff, AZ it runs 85–257 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 75–100 °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 Flagstaff, AZ
Every spring job for 63 crop dates, counted from this metro's own last spring freeze. Each is a range across all 19 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 | January 8 – April 26 | 8 weeks before |
| Peppers | Start indoors | January 8 – April 26 | 8 weeks before |
| Broccoli | Start indoors | January 22 – May 10 | 6 weeks before |
| Cabbage | Start indoors | January 22 – May 10 | 6 weeks before |
| Collards | Start indoors | January 22 – May 10 | 6 weeks before |
| Kale | Start indoors | January 22 – May 10 | 6 weeks before |
| Leaf Lettuce | Start indoors | January 22 – May 10 | 6 weeks before |
| Peas | Direct sow | January 22 – May 10 | 6 weeks before |
| Spinach | Direct sow | January 22 – May 10 | 6 weeks before |
| Sweet Potato | Start indoors | January 22 – May 10 | 6 weeks before |
| Tomatoes | Start indoors | January 22 – May 10 | 6 weeks before |
| Bok Choy | Start indoors | January 29 – May 17 | 5 weeks before |
| Kohlrabi | Start indoors | January 29 – May 17 | 5 weeks before |
| Swiss Chard | Start indoors | January 29 – May 17 | 5 weeks before |
| Arugula | Direct sow | February 5 – May 24 | 4 weeks before |
| Baby Salad Greens | Direct sow | February 5 – May 24 | 4 weeks before |
| Beets | Direct sow | February 5 – May 24 | 4 weeks before |
| Green Onions | Direct sow | February 5 – May 24 | 4 weeks before |
| Mustard Greens | Direct sow | February 5 – May 24 | 4 weeks before |
| Okra | Start indoors | February 5 – May 24 | 4 weeks before |
| Radishes | Direct sow | February 5 – May 24 | 4 weeks before |
| Turnips | Direct sow | February 5 – May 24 | 4 weeks before |
| Cabbage | Set out | February 12 – May 31 | 3 weeks before |
| Carrots | Direct sow | February 12 – May 31 | 3 weeks before |
| Collards | Direct sow | February 12 – May 31 | 3 weeks before |
| Collards | Set out | February 12 – May 31 | 3 weeks before |
| Cucumbers | Start indoors | February 12 – May 31 | 3 weeks before |
| Green Onions | Set out | February 12 – May 31 | 3 weeks before |
| Kale | Direct sow | February 12 – May 31 | 3 weeks before |
| Kale | Set out | February 12 – May 31 | 3 weeks before |
| Kohlrabi | Direct sow | February 12 – May 31 | 3 weeks before |
| Kohlrabi | Set out | February 12 – May 31 | 3 weeks before |
| Leaf Lettuce | Direct sow | February 12 – May 31 | 3 weeks before |
| Pumpkins | Start indoors | February 12 – May 31 | 3 weeks before |
| Summer Squash | Start indoors | February 12 – May 31 | 3 weeks before |
| Winter Squash | Start indoors | February 12 – May 31 | 3 weeks before |
| Zucchini | Start indoors | February 12 – May 31 | 3 weeks before |
| Bok Choy | Direct sow | February 19 – June 7 | 2 weeks before |
| Bok Choy | Set out | February 19 – June 7 | 2 weeks before |
| Broccoli | Set out | February 19 – June 7 | 2 weeks before |
| Cilantro | Direct sow | February 19 – June 7 | 2 weeks before |
| Leaf Lettuce | Set out | February 19 – June 7 | 2 weeks before |
| Swiss Chard | Direct sow | February 19 – June 7 | 2 weeks before |
| Swiss Chard | Set out | February 19 – June 7 | 2 weeks before |
| Dill | Direct sow | February 26 – June 14 | 1 week before |
| Bush Beans | Direct sow | March 12 – June 28 | 1 week after |
| Cucumbers | Set out | March 12 – June 28 | 1 week after |
| Pumpkins | Direct sow | March 12 – June 28 | 1 week after |
| Pumpkins | Set out | March 12 – June 28 | 1 week after |
| Summer Squash | Direct sow | March 12 – June 28 | 1 week after |
| Summer Squash | Set out | March 12 – June 28 | 1 week after |
| Sweet Corn | Direct sow | March 12 – June 28 | 1 week after |
| Tomatoes | Set out | March 12 – June 28 | 1 week after |
| Winter Squash | Direct sow | March 12 – June 28 | 1 week after |
| Winter Squash | Set out | March 12 – June 28 | 1 week after |
| Zucchini | Direct sow | March 12 – June 28 | 1 week after |
| Zucchini | Set out | March 12 – June 28 | 1 week after |
| Cucumbers | Direct sow | March 19 – July 5 | 2 weeks after |
| Okra | Direct sow | March 19 – July 5 | 2 weeks after |
| Okra | Set out | March 19 – July 5 | 2 weeks after |
| Peppers | Set out | March 19 – July 5 | 2 weeks after |
| Southern Peas | Direct sow | March 19 – July 5 | 2 weeks after |
| Sweet Potato | Set out | March 19 – July 5 | 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 Flagstaff, AZ
Of 74 perennial fruits, nuts, berries, vegetables and herbs, 58 come through the winter in zone 7a and only 48 in zone 5b. That is a different garden at each end of the same metro.
| Zone | ZIPs | Survive | Fail for being too warm |
|---|---|---|---|
| 5b | 1 | 48 of 74 | 0 |
| 6a | 2 | 51 of 74 | 0 |
| 6b | 6 | 51 of 74 | 0 |
| 7a | 11 | 58 of 74 | 1 |
| 7b | 5 | 56 of 74 | 3 |
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 19 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 |
|---|---|---|---|---|
| Bellemont Wfo, AZ | USC00020678 | June 21 | September 17 | 85 days |
| Betatakin, AZ | USC00020750 | May 7 | October 15 | 159 days |
| Blue Ridge RS, AZ | USC00020871 | May 31 | October 2 | 126 days |
| Bright Angel RS, AZ | USC00021001 | June 3 | September 27 | 113 days |
| Flagstaff Pulliam AP, AZ | USW00003103 | June 4 | September 28 | 115 days |
| Ft Valley, AZ | USC00023160 | June 11 | September 25 | 99 days |
| Grand Canyon Visitor Ctr, AZ | USC00023582 | May 2 | October 27 | 177 days |
| Lees Ferry, AZ | USC00024849 | March 5 | November 19 | 257 days |
| Mund'S Park, AZ | USC00025780 | June 10 | September 27 | 106 days |
| Page, AZ | USC00026180 | March 27 | November 9 | 226 days |
| Pipe Spring Nm, AZ | USC00026616 | May 1 | October 19 | 168 days |
| Pleasant Valley, AZ | USC00026653 | May 6 | October 20 | 165 days |
| Seligman, AZ | USC00027716 | May 10 | October 15 | 154 days |
| Sunset Crater Nm, AZ | USC00028329 | June 16 | September 19 | 94 days |
| Tuba City, AZ | USC00028792 | April 16 | October 28 | 193 days |
| Twin Arrows, AZ | USC00028910 | April 14 | October 25 | 192 days |
| Williams 35 Nnw, AZ | USW00053155 | May 9 | October 19 | 161 days |
| Williams, AZ | USC00029359 | May 22 | October 5 | 135 days |
| Wupatki Nm, AZ | USC00029542 | April 7 | November 3 | 206 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 Flagstaff, AZ 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.