Gardening in Kahului-Wailuku, HI
This metro spans USDA zones 11b to 12b, so there is no single zone for Kahului-Wailuku, HI and anyone who gives you one is rounding. 67% of its ZIP codes are zone 12b; the rest are not.
Which zone you are in depends where you are
Kahului-Wailuku, HI 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 67% in zone 12b and wrong for the other 33%. Here is the actual split.
| Zone | ZIP codes | Share | |
|---|---|---|---|
| 12b | 10 | 67% | |
| 12a | 4 | 27% | |
| 11b | 1 | 7% |
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
No freeze range is shown for Kahului-Wailuku, HI, because at least one station here records no freeze at any probability, so there is no date to average. The tools below still answer for individual ZIP codes here, and will say what applies.
Your growing season
NOAA publishes a growing-season length for each station, and across the 9 stations serving Kahului-Wailuku, HI it runs 365 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 66–89 °F , below the 90 °F point where cool-season crops reliably bolt.
What survives the winter changes across Kahului-Wailuku, HI
Of 74 perennial fruits, nuts, berries, vegetables and herbs, 18 come through the winter in zone 11b and only 14 in zone 12a. That is a different garden at each end of the same metro.
| Zone | ZIPs | Survive | Fail for being too warm |
|---|---|---|---|
| 11b | 1 | 18 of 74 | 56 |
| 12a | 4 | 14 of 74 | 60 |
| 12b | 10 | 14 of 74 | 60 |
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 9 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 |
|---|---|---|---|---|
| Haleakala RS 338, HI | USC00511004 | no freeze recorded | no freeze recorded | 365 days |
| Kahului AP, HI | USW00022516 | no freeze recorded | no freeze recorded | 365 days |
| Kula Branch Stn 324.5, HI | USC00515000 | no freeze recorded | no freeze recorded | 365 days |
| Kula Hospital 267, HI | USC00515004 | no freeze recorded | no freeze recorded | 365 days |
| Lanai AP 656, HI | USC00515275 | no freeze recorded | no freeze recorded | 365 days |
| Molokai AP, HI | USW00022534 | no freeze recorded | no freeze recorded | 365 days |
| Ohe'O 258.6, HI | USC00517000 | no freeze recorded | no freeze recorded | 365 days |
| Puu-O-Hoku Rch 542.1, HI | USC00518549 | no freeze recorded | no freeze recorded | 365 days |
| Puukolii 457.1, HI | USC00518407 | no freeze recorded | no freeze recorded | 365 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 Kahului-Wailuku, HI 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.