Phoenix, AZ Vegetable Planting Calendar
When to plant 26 vegetables in Phoenix, for the 2027 season, based on 1991–2020 normals. The dates build on the 32°F frost odds at Phoenix Deer Valley Municipal Airport (8.0 mi N), shifted by CSU Extension timing rules. You'll find each rule and its source below.
NOAA puts the yearly chance of at least one 32°F night at Phoenix Deer Valley Municipal Airport at 70.2%. The dates below come from the frost odds for the years that do freeze.
These are Colorado State University Extension (spring) and University of Nebraska–Lincoln Extension (fall) timing rules, applied to Phoenix's own NOAA frost dates. Arizona extension guidance may differ, so check it too.
Frost anchors: typical last frost Jan 8 (50%), balanced Jan 23 (30%), safe Feb 12 (10%); typical first frost Dec 25. Station Phoenix Deer Valley Municipal Airport (USW00003184), confidence High. USDA zone 9b–10a (2023). Phoenix frost dates & growing zone.
What to plant now in Phoenix
In October:
- Last day to sow carrots for a fall harvest (by Oct 2)
- Last day to sow cucumbers for a fall harvest (by Oct 3)
- Last day to sow peas for a fall harvest (by Oct 7)
- Last day to set out broccoli transplants for a fall harvest (by Oct 7)
- Last day to sow summer squash for a fall harvest (by Oct 8)
- Last day to sow lettuce (leaf) for a fall harvest (by Oct 12)
- Last day to sow green onions for a fall harvest (by Oct 12)
- Last day to sow beets for a fall harvest (by Oct 12)
- Last day to sow swiss chard for a fall harvest (by Oct 12)
- Last day to sow kohlrabi for a fall harvest (by Oct 22)
- Last day to sow turnips for a fall harvest (by Oct 22)
The list above is for the month this page was built; the box is refreshed in your browser for today's date.
Spring planting dates
“Plant out” means transplanting for crops started indoors and sowing or planting directly in the garden for the others. Each column applies CSU Extension's timing rule to a different last-frost anchor: aggressive = typical date (Jan 8, 50% risk), balanced = Jan 23 (30%), safe = Feb 12 (10%). For hardy crops the cell shows the CSU “as early as” window.
| Crop | How | Start indoors | Plant out: aggressive (50%) | Balanced (30%) | Safe (10%) | Min. soil temp |
|---|---|---|---|---|---|---|
| Tomatoes Very tender (warm season) |
transplant | Feb 3–17 | Mar 24 | Mar 24 | Mar 24 | 50°F |
| Peppers Very tender (warm season) |
transplant | Dec 12–26 | Jan 22 | Feb 6 | Feb 26 | 60°F |
| Potatoes Semi-hardy (cool season) |
plant (seed pieces) | – | Dec 25 – Jan 8 | Jan 9–23 | Jan 29 – Feb 12 | 45°F |
| Onions (dry, from sets) Hardy (cool season) |
plant sets | – | Dec 11–25 | Dec 26 – Jan 9 | Jan 15–29 | 35°F |
| Peas Hardy (cool season) |
direct sow | – | Dec 11–25 | Dec 26 – Jan 9 | Jan 15–29 | 40°F |
| Lettuce (leaf) Hardy (cool season) |
direct sow | – | Dec 11–25 | Dec 26 – Jan 9 | Jan 15–29 | 35°F |
| Carrots Semi-hardy (cool season) |
direct sow | – | Dec 25 – Jan 8 | Jan 9–23 | Jan 29 – Feb 12 | 40°F |
| Beans (snap) Tender (warm season) |
direct sow | – | Jan 8 | Jan 23 | Feb 12 | 55°F |
| Summer squash Tender (warm season) |
direct sow | – | Jan 8 | Jan 23 | Feb 12 | 60°F |
| Broccoli Hardy (cool season) |
transplant | Nov 7–21 | Dec 11–25 | Dec 26 – Jan 9 | Jan 15–29 | 40°F |
| Cabbage Hardy (cool season) |
transplant | Nov 7–21 | Dec 11–25 | Dec 26 – Jan 9 | Jan 15–29 | 40°F |
| Cauliflower Semi-hardy (cool season) |
transplant | Nov 21 – Dec 5 | Dec 25 – Jan 8 | Jan 9–23 | Jan 29 – Feb 12 | 40°F |
| Kohlrabi Hardy (cool season) |
direct sow | – | Dec 11–25 | Dec 26 – Jan 9 | Jan 15–29 | 40°F |
| Green onions Hardy (cool season) |
direct sow | – | Dec 11–25 | Dec 26 – Jan 9 | Jan 15–29 | 35°F |
| Radishes Hardy (cool season) |
direct sow | – | Dec 11–25 | Dec 26 – Jan 9 | Jan 15–29 | 40°F |
| Spinach Hardy (cool season) |
direct sow | – | Dec 11–25 | Dec 26 – Jan 9 | Jan 15–29 | 40°F |
| Turnips Hardy (cool season) |
direct sow | – | Dec 11–25 | Dec 26 – Jan 9 | Jan 15–29 | 40°F |
| Beets Semi-hardy (cool season) |
direct sow | – | Dec 25 – Jan 8 | Jan 9–23 | Jan 29 – Feb 12 | 40°F |
| Swiss chard Semi-hardy (cool season) |
direct sow | – | Dec 25 – Jan 8 | Jan 9–23 | Jan 29 – Feb 12 | 40°F |
| Parsnips Semi-hardy (cool season) |
direct sow | – | Dec 25 – Jan 8 | Jan 9–23 | Jan 29 – Feb 12 | 35°F |
| Sweet corn Tender (warm season) |
direct sow | – | Jan 8 | Jan 23 | Feb 12 | 50°F |
| Cucumbers Tender (warm season) |
direct sow | – | Jan 8 | Jan 23 | Feb 12 | 60°F |
| Eggplant Very tender (warm season) |
transplant | Dec 5–26 | Jan 22 | Feb 6 | Feb 26 | 60°F |
| Cantaloupe Very tender (warm season) |
direct sow | – | Jan 22 | Feb 6 | Feb 26 | 60°F |
| Watermelon Very tender (warm season) |
direct sow | – | Jan 22 | Feb 6 | Feb 26 | 60°F |
| Winter squash Very tender (warm season) |
direct sow | – | Jan 22 | Feb 6 | Feb 26 | 60°F |
A soil thermometer helps here. CSU recommends checking soil temperature at 4 inches (6 inches for beans) before sowing. NOAA doesn't publish soil-temperature normals, so instead of a date, each crop shows CSU's minimum soil temperature.
Fall planting dates
Latest dates for a fall harvest, using the University of Nebraska–Lincoln Extension count-back formula: days to harvest (CSU) + 14-day fall factor + 14-day frost-tender factor for frost-sensitive crops, counted back from the first-frost date. For transplanted crops (CSU days are from transplant) the result is the latest transplant date; seeds go in CSU's transplant-age weeks earlier. We add no harvest period, so these dates give you a first harvest by the first frost, not a long harvest.
| Crop | How | Days counted back | By (typical first frost Dec 25) | By (early first frost Dec 5) |
|---|---|---|---|---|
| Peas | sow | 79 | Oct 7 | Sep 17 |
| Lettuce (leaf) | sow | 74 | Oct 12 | Sep 22 |
| Carrots | sow | 84 | Oct 2 | Sep 12 |
| Beans (snap) | sow | 88 (frost-tender) | Sep 28 | Sep 8 |
| Summer squash | sow | 78 (frost-tender) | Oct 8 | Sep 18 |
| Broccoli | transplant (start seeds Aug 19 – Sep 2) | 79 | Oct 7 | Sep 17 |
| Cabbage | transplant (start seeds Jul 30 – Aug 13) | 99 | Sep 17 | Aug 28 |
| Kohlrabi | sow | 64 | Oct 22 | Oct 2 |
| Green onions | sow | 74 | Oct 12 | Sep 22 |
| Radishes | sow | 44 | Nov 11 | Oct 22 |
| Spinach | sow | 54 | Nov 1 | Oct 12 |
| Turnips | sow | 64 | Oct 22 | Oct 2 |
| Beets | sow | 74 | Oct 12 | Sep 22 |
| Swiss chard | sow | 74 | Oct 12 | Sep 22 |
| Cucumbers | sow | 83 (frost-tender) | Oct 3 | Sep 13 |
Month-by-month: what to plant in Phoenix
What to plant in Phoenix in January
- Beans (snap): direct sow outdoors (Jan 8 – Feb 12)
- Summer squash: direct sow outdoors (Jan 8 – Feb 12)
- Sweet corn: direct sow outdoors (Jan 8 – Feb 12)
- Cucumbers: direct sow outdoors (Jan 8 – Feb 12)
- Peppers: transplant outdoors (Jan 22 – Feb 26)
- Eggplant: transplant outdoors (Jan 22 – Feb 26)
- Cantaloupe: direct sow outdoors (Jan 22 – Feb 26)
- Watermelon: direct sow outdoors (Jan 22 – Feb 26)
- Winter squash: direct sow outdoors (Jan 22 – Feb 26)
- Onions (dry, from sets): plant sets outdoors (Dec 11 – Jan 29)
- Peas: direct sow outdoors (Dec 11 – Jan 29)
- Lettuce (leaf): direct sow outdoors (Dec 11 – Jan 29)
- Broccoli: transplant outdoors (Dec 11 – Jan 29)
- Cabbage: transplant outdoors (Dec 11 – Jan 29)
- Kohlrabi: direct sow outdoors (Dec 11 – Jan 29)
- Green onions: direct sow outdoors (Dec 11 – Jan 29)
- Radishes: direct sow outdoors (Dec 11 – Jan 29)
- Spinach: direct sow outdoors (Dec 11 – Jan 29)
- Turnips: direct sow outdoors (Dec 11 – Jan 29)
- Potatoes: plant (seed pieces) outdoors (Dec 25 – Feb 12)
- Carrots: direct sow outdoors (Dec 25 – Feb 12)
- Cauliflower: transplant outdoors (Dec 25 – Feb 12)
- Beets: direct sow outdoors (Dec 25 – Feb 12)
- Swiss chard: direct sow outdoors (Dec 25 – Feb 12)
- Parsnips: direct sow outdoors (Dec 25 – Feb 12)
What to plant in Phoenix in February
- Start tomato seeds indoors (Feb 3–17)
- Potatoes: plant (seed pieces) outdoors (Dec 25 – Feb 12)
- Carrots: direct sow outdoors (Dec 25 – Feb 12)
- Cauliflower: transplant outdoors (Dec 25 – Feb 12)
- Beets: direct sow outdoors (Dec 25 – Feb 12)
- Swiss chard: direct sow outdoors (Dec 25 – Feb 12)
- Parsnips: direct sow outdoors (Dec 25 – Feb 12)
- Beans (snap): direct sow outdoors (Jan 8 – Feb 12)
- Summer squash: direct sow outdoors (Jan 8 – Feb 12)
- Sweet corn: direct sow outdoors (Jan 8 – Feb 12)
- Cucumbers: direct sow outdoors (Jan 8 – Feb 12)
- Peppers: transplant outdoors (Jan 22 – Feb 26)
- Eggplant: transplant outdoors (Jan 22 – Feb 26)
- Cantaloupe: direct sow outdoors (Jan 22 – Feb 26)
- Watermelon: direct sow outdoors (Jan 22 – Feb 26)
- Winter squash: direct sow outdoors (Jan 22 – Feb 26)
What to plant in Phoenix in March
- Tomatoes: transplant outdoors (Mar 24)
What to plant in Phoenix in July
- Start cabbage seeds indoors for a fall crop (Jul 30 – Aug 13)
What to plant in Phoenix in August
- Start broccoli seeds indoors for a fall crop (Aug 19 – Sep 2)
- Start cabbage seeds indoors for a fall crop (Jul 30 – Aug 13)
What to plant in Phoenix in September
- Last day to set out cabbage transplants for a fall harvest (by Sep 17)
- Last day to sow beans (snap) for a fall harvest (by Sep 28)
- Start broccoli seeds indoors for a fall crop (Aug 19 – Sep 2)
What to plant in Phoenix in October
- Last day to sow carrots for a fall harvest (by Oct 2)
- Last day to sow cucumbers for a fall harvest (by Oct 3)
- Last day to sow peas for a fall harvest (by Oct 7)
- Last day to set out broccoli transplants for a fall harvest (by Oct 7)
- Last day to sow summer squash for a fall harvest (by Oct 8)
- Last day to sow lettuce (leaf) for a fall harvest (by Oct 12)
- Last day to sow green onions for a fall harvest (by Oct 12)
- Last day to sow beets for a fall harvest (by Oct 12)
- Last day to sow swiss chard for a fall harvest (by Oct 12)
- Last day to sow kohlrabi for a fall harvest (by Oct 22)
- Last day to sow turnips for a fall harvest (by Oct 22)
What to plant in Phoenix in November
- Start broccoli seeds indoors (Nov 7–21)
- Start cabbage seeds indoors (Nov 7–21)
- Start cauliflower seeds indoors (Nov 21 – Dec 5)
- Last day to sow spinach for a fall harvest (by Nov 1)
- Last day to sow radishes for a fall harvest (by Nov 11)
What to plant in Phoenix in December
- Start eggplant seeds indoors (Dec 5–26)
- Onions (dry, from sets): plant sets outdoors (Dec 11 – Jan 29)
- Peas: direct sow outdoors (Dec 11 – Jan 29)
- Lettuce (leaf): direct sow outdoors (Dec 11 – Jan 29)
- Broccoli: transplant outdoors (Dec 11 – Jan 29)
- Cabbage: transplant outdoors (Dec 11 – Jan 29)
- Kohlrabi: direct sow outdoors (Dec 11 – Jan 29)
- Green onions: direct sow outdoors (Dec 11 – Jan 29)
- Radishes: direct sow outdoors (Dec 11 – Jan 29)
- Spinach: direct sow outdoors (Dec 11 – Jan 29)
- Turnips: direct sow outdoors (Dec 11 – Jan 29)
- Start pepper seeds indoors (Dec 12–26)
- Potatoes: plant (seed pieces) outdoors (Dec 25 – Feb 12)
- Carrots: direct sow outdoors (Dec 25 – Feb 12)
- Cauliflower: transplant outdoors (Dec 25 – Feb 12)
- Beets: direct sow outdoors (Dec 25 – Feb 12)
- Swiss chard: direct sow outdoors (Dec 25 – Feb 12)
- Parsnips: direct sow outdoors (Dec 25 – Feb 12)
- Start cauliflower seeds indoors (Nov 21 – Dec 5)
Crop-by-crop notes
When to plant tomatoes in Phoenix
Very tender crop. CSU Extension says to transplant tomatoes at least 2 weeks after the average last frost, with nights above 52°F. The frost rule alone would put Phoenix at about Jan 22, but the average nightly low at Phoenix Deer Valley Municipal Airport isn't above 52°F until Mar 24, so the transplant date is about Mar 24 for the typical, balanced and safer choices alike. Start seeds indoors Feb 3–17, 5–7 weeks before transplanting on Mar 24. CSU notes that nights under 55°F hurt fruit set. The normal low at Phoenix Deer Valley Municipal Airport climbs to 55°F on Apr 10. Using CSU's typical 65 days from transplant to harvest, tomato plants set out on Mar 24 would start producing around May 28. That's 211 days before the typical first frost (Dec 25).
When to plant peppers in Phoenix
Very tender crop. CSU Extension's rule is to set peppers out at least 2 weeks after the average last frost. That's about Jan 22 using the typical date, Feb 6 as a balanced choice, or Feb 26 if you go by the safer 10% date. Start seeds indoors Dec 12–26, 6–8 weeks before transplanting on Feb 6. CSU notes that nights under 55°F hurt fruit set. The normal low at Phoenix Deer Valley Municipal Airport climbs to 55°F on Apr 10. Set out on Feb 6, pepper plants would start producing around Apr 17, based on CSU's typical 70 days from transplant to harvest. That leaves 252 days before the typical first frost (Dec 25).
When to plant potatoes in Phoenix
Semi-hardy crop. CSU allows planting potatoes as early as 0–2 weeks before the average last frost, in soil at 45°F or warmer. For Phoenix, that's roughly Dec 25 – Jan 8 by the typical date or Jan 29 – Feb 12 by the safer date.
When to plant onions (dry, from sets) in Phoenix
Hardy crop. Per CSU, onions (dry, from sets) can be planted as early as 2–4 weeks before the average last frost, as long as the soil is workable and at least 35°F. For Phoenix, that works out to roughly Dec 11–25 (typical date) or Jan 15–29 (safer date).
When to plant peas in Phoenix
Hardy crop. CSU says peas can go in as early as 2–4 weeks before the average last frost, once the soil can be worked and is at least 40°F. In Phoenix, that's roughly Dec 11–25 going by the typical date, or Jan 15–29 going by the safer date. For a fall crop, sow by Oct 7, or by Sep 17 to be safe. That's 79 days back from the first-frost date.
When to plant lettuce (leaf) in Phoenix
Hardy crop. CSU says lettuce (leaf) can go in as early as 2–4 weeks before the average last frost, once the soil can be worked and is at least 35°F. In Phoenix, that's roughly Dec 11–25 going by the typical date, or Jan 15–29 going by the safer date. For a fall crop, sow by Oct 12, or by Sep 22 to be safe. That's 74 days back from the first-frost date.
When to plant carrots in Phoenix
Semi-hardy crop. Per CSU, carrots can go in as early as 0–2 weeks before the average last frost: roughly Dec 25 – Jan 8 in Phoenix (typical date) or Jan 29 – Feb 12 (safer date). The soil should be at least 40°F. For fall, count back 84 days from the first-frost date. That means sowing by Oct 2, or by Sep 12 to be safe.
When to plant beans (snap) in Phoenix
Tender crop. CSU's timing for beans (snap) is around the average last frost, which is about Jan 8 in Phoenix. For only a 1-in-10 chance of a later 32°F night, hold off until Feb 12. Seeds want soil at 55°F or warmer. For fall, sow by Sep 28 (Sep 8 to be safe), which is 88 days before the first-frost date.
When to plant summer squash in Phoenix
Tender crop. CSU says to sow summer squash around the average last frost, about Jan 8 in Phoenix. If you want only a 1-in-10 chance of a later 32°F night, wait until Feb 12. Seeds need soil of at least 60°F. For a fall crop, sow by Oct 8, or by Sep 18 to be safe. That's 78 days back from the first-frost date.
When to plant broccoli in Phoenix
Hardy crop. CSU says broccoli can go in as early as 2–4 weeks before the average last frost: roughly Dec 11–25 in Phoenix using the typical date, or Jan 15–29 using the safer one. Wait until the soil can be worked and is at least 40°F. CSU's typical time from transplant to harvest for broccoli plants is 65 days. Set out on Dec 26, they would start producing around Mar 1, 299 days before the typical first frost (Dec 25). For a fall harvest of broccoli, get transplants in the ground by Oct 7 (UNL Extension count-back from the typical first frost, Dec 25, with CSU's 65 days from transplant to harvest). To raise your own, sow seeds Aug 19 – Sep 2, 5–7 weeks ahead (CSU).
When to plant cabbage in Phoenix
Hardy crop. CSU says cabbage can go in as early as 2–4 weeks before the average last frost, once the soil can be worked and is at least 40°F. In Phoenix, that's roughly Dec 11–25 going by the typical date, or Jan 15–29 going by the safer date. CSU's typical time from transplant to harvest for cabbage plants is 85 days. Set out on Dec 26, they would start producing around Mar 21, 279 days before the typical first frost (Dec 25). For a fall harvest of cabbage, get transplants in the ground by Sep 17 (UNL Extension count-back from the typical first frost, Dec 25, with CSU's 85 days from transplant to harvest). To raise your own, sow seeds Jul 30 – Aug 13, 5–7 weeks ahead (CSU).
When to plant cauliflower in Phoenix
Semi-hardy crop. Per CSU, cauliflower can go in as early as 0–2 weeks before the average last frost: roughly Dec 25 – Jan 8 in Phoenix (typical date) or Jan 29 – Feb 12 (safer date). The soil should be at least 40°F.
When to plant kohlrabi in Phoenix
Hardy crop. CSU says kohlrabi can go in as early as 2–4 weeks before the average last frost, once the soil can be worked and is at least 40°F. In Phoenix, that's roughly Dec 11–25 going by the typical date, or Jan 15–29 going by the safer date. For fall, sow by Oct 22 (Oct 2 to be safe), which is 64 days before the first-frost date.
When to plant green onions in Phoenix
Hardy crop. CSU says green onions can go in as early as 2–4 weeks before the average last frost: roughly Dec 11–25 in Phoenix using the typical date, or Jan 15–29 using the safer one. Wait until the soil can be worked and is at least 35°F. For fall, sow by Oct 12 (Sep 22 to be safe), which is 74 days before the first-frost date.
When to plant radishes in Phoenix
Hardy crop. CSU says radishes can go in as early as 2–4 weeks before the average last frost: roughly Dec 11–25 in Phoenix using the typical date, or Jan 15–29 using the safer one. Wait until the soil can be worked and is at least 40°F. For a fall crop, sow by Nov 11, or by Oct 22 to be safe. That's 44 days back from the first-frost date.
When to plant spinach in Phoenix
Hardy crop. CSU says spinach can go in as early as 2–4 weeks before the average last frost: roughly Dec 11–25 in Phoenix using the typical date, or Jan 15–29 using the safer one. Wait until the soil can be worked and is at least 40°F. For fall, sow by Nov 1 (Oct 12 to be safe), which is 54 days before the first-frost date.
When to plant turnips in Phoenix
Hardy crop. CSU says turnips can go in as early as 2–4 weeks before the average last frost, once the soil can be worked and is at least 40°F. In Phoenix, that's roughly Dec 11–25 going by the typical date, or Jan 15–29 going by the safer date. For fall, sow by Oct 22 (Oct 2 to be safe), which is 64 days before the first-frost date.
When to plant beets in Phoenix
Semi-hardy crop. CSU allows planting beets as early as 0–2 weeks before the average last frost, in soil at 40°F or warmer. For Phoenix, that's roughly Dec 25 – Jan 8 by the typical date or Jan 29 – Feb 12 by the safer date. For fall, count back 74 days from the first-frost date. That means sowing by Oct 12, or by Sep 22 to be safe.
When to plant swiss chard in Phoenix
Semi-hardy crop. Per CSU, swiss chard can go in as early as 0–2 weeks before the average last frost: roughly Dec 25 – Jan 8 in Phoenix (typical date) or Jan 29 – Feb 12 (safer date). The soil should be at least 40°F. For fall, sow by Oct 12 (Sep 22 to be safe), which is 74 days before the first-frost date.
When to plant parsnips in Phoenix
Semi-hardy crop. Per CSU, parsnips can go in as early as 0–2 weeks before the average last frost: roughly Dec 25 – Jan 8 in Phoenix (typical date) or Jan 29 – Feb 12 (safer date). The soil should be at least 35°F.
When to plant sweet corn in Phoenix
Tender crop. CSU says to sow sweet corn around the average last frost, about Jan 8 in Phoenix. If you want only a 1-in-10 chance of a later 32°F night, wait until Feb 12. Seeds need soil of at least 50°F.
When to plant cucumbers in Phoenix
Tender crop. CSU's timing for cucumbers is around the average last frost, which is about Jan 8 in Phoenix. For only a 1-in-10 chance of a later 32°F night, hold off until Feb 12. Seeds want soil at 60°F or warmer. For fall, count back 83 days from the first-frost date. That means sowing by Oct 3, or by Sep 13 to be safe.
When to plant eggplant in Phoenix
Very tender crop. Following CSU Extension's rule (2+ weeks after the average last frost), set eggplant out around Jan 22 with the typical date, Feb 6 for a balanced choice, or Feb 26 with the safer 10% date. Sow seeds indoors Dec 5–26, 6–9 weeks before transplanting on Feb 6. Using CSU's typical 60 days from transplant to harvest, eggplant plants set out on Feb 6 would start producing around Apr 7. That's 262 days before the typical first frost (Dec 25).
When to plant cantaloupe in Phoenix
Very tender crop. CSU Extension says to plant cantaloupe 2+ weeks after the average last frost: about Jan 22 (typical date), Feb 6 (balanced) or Feb 26 (safer 10% date). Wait for soil of at least 60°F.
When to plant watermelon in Phoenix
Very tender crop. CSU Extension says to plant watermelon 2+ weeks after the average last frost: about Jan 22 (typical date), Feb 6 (balanced) or Feb 26 (safer 10% date). Wait for soil of at least 60°F.
When to plant winter squash in Phoenix
Very tender crop. Following CSU Extension's rule of 2+ weeks after the average last frost, plant winter squash around Jan 22 at the earliest, Feb 6 as a balanced choice, or Feb 26 to be safe. CSU's minimum soil temperature is 60°F.
How these dates are calculated
| Rule | Applies to | Source (scope) |
|---|---|---|
| Hardy (cool season): “As early as 2-4 weeks before the date of the average last spring frost.” | Onions (dry, from sets), Peas, Lettuce (leaf), Broccoli, Cabbage, Kohlrabi, Green onions, Radishes, Spinach, Turnips | Colorado State University Extension, Vegetable Planting Guide (CMG GardenNotes #720) (written for Colorado; its frost-relative rules are applied to other states' NOAA frost dates and labelled as CSU (Colorado) rules) |
| Semi-hardy (cool season): “As early as 0-2 weeks before the date of the average last spring frost.” | Potatoes, Carrots, Cauliflower, Beets, Swiss chard, Parsnips | Colorado State University Extension, Vegetable Planting Guide (CMG GardenNotes #720) (written for Colorado; its frost-relative rules are applied to other states' NOAA frost dates and labelled as CSU (Colorado) rules) |
| Tender (warm season): “From seed: around the date of the average last spring frost” | Beans (snap), Summer squash, Sweet corn, Cucumbers | Colorado State University Extension, Vegetable Planting Guide (CMG GardenNotes #720) (written for Colorado; its frost-relative rules are applied to other states' NOAA frost dates and labelled as CSU (Colorado) rules) |
| Very tender (warm season): “Typically 2+ weeks after the average last spring frost date.” | Tomatoes, Peppers, Eggplant, Cantaloupe, Watermelon, Winter squash | Colorado State University Extension, Vegetable Planting Guide (CMG GardenNotes #720) (written for Colorado; its frost-relative rules are applied to other states' NOAA frost dates and labelled as CSU (Colorado) rules) |
| Start indoors = transplant age (weeks) before the balanced transplant date; days to harvest; minimum soil temperature | Crops with those values in CSU's table | CSU Extension, Vegetable Planting Guide (CMG GardenNotes #720) (written for Colorado; its frost-relative rules are applied to other states' NOAA frost dates and labelled as CSU (Colorado) rules) |
| Night-temperature dates: first day the NOAA 1991–2020 daily normal low (DLY-TMIN-NORMAL) is above the CSU transplant threshold or reaches the fruit-set threshold | Tomatoes (above 52°F at transplant, 55°F fruit set), peppers (55°F fruit set) | CSU Growing Tomatoes, CSU Peppers and Eggplants (written for Colorado; generic temperature thresholds applied nationwide with attribution) |
| Fall count-back: days to harvest + fall factor (14) + frost-tender factor (14) | Peas, Lettuce (leaf), Carrots, Beans (snap), Summer squash, Broccoli, Cabbage, Kohlrabi, Green onions, Radishes, Spinach, Turnips, Beets, Swiss chard, Cucumbers | UNL Extension, Fall Vegetable Gardening (G1343) (written for Nebraska; the count-back formula is applied nationwide with attribution) |
CSU states its spring rules relative to “the average last spring frost.” We use the 50% date as that average and also show the 30% and 10% anchors. See the methodology for details and limitations.
FAQ
When should I start seeds indoors in Phoenix?
Start tomatoes Feb 3–17 and peppers Dec 12–26. Both dates count back from a balanced (30%-risk) transplant date using CSU's transplant ages.
When should I plant tomatoes outside in Phoenix?
About Mar 24, at every risk level. CSU wants tomatoes out 2+ weeks after the average last frost (that rule alone gives about Jan 22 here) and nights above 52°F. At Phoenix Deer Valley Municipal Airport, the average nightly low first rises above 52°F on Mar 24, later than the frost-rule date, so the night rule sets the date.
What can I plant in Phoenix in the fall?
Based on UNL Extension's count-back from the typical first frost (Dec 25), the deadlines are: peas by Oct 7; lettuce (leaf) by Oct 12; carrots by Oct 2; beans (snap) by Sep 28; summer squash by Oct 8; broccoli by Oct 7 (transplants); cabbage by Sep 17 (transplants); kohlrabi by Oct 22; green onions by Oct 12; radishes by Nov 11; spinach by Nov 1; turnips by Oct 22; beets by Oct 12; swiss chard by Oct 12; cucumbers by Oct 3.