The short answer for Hawaii
A mainland planting calendar starts from frost dates, and a frost date is a probability: the day by which there is, say, a 10, 50 or 90 percent chance that the temperature has dropped to 32°F or 36°F for the last time in spring or the first time in fall. Hawaii has no such date. The NOAA NCEI 1991-2020 Climate Normals for the Honolulu station (USW00022521) show zero days per year at or below 32°F, and every freeze percentile at 32°F and 36°F comes back flagged “not computable.” You cannot calculate a probability for something that does not happen. You can see the NOAA normals data for that station yourself.
Frost does occur on the high volcanic summits (Mauna Kea, Mauna Loa and Haleakala), but nobody gardens there. In every place where people actually grow food, the “last frost” and “first frost” lines on a seed packet are blank.
What replaces the frost date
Honolulu’s coldest month still has a mean daily minimum of 66.8°F. That is the nightly low in the chilliest stretch of the year, and it is warmer than a mild spring night in much of the continental U.S. Shallots are a cool-season crop at heart, so the question here is never “when is it safe?” It is “when is it cool enough, and dry enough, for the bulbs to size up and cure?”
Three things answer that question in practice:
- Rainfall pattern: bulbs swell in steady moisture but need drier weather as the tops fall over and the bulbs mature.
- Elevation: a higher garden runs cooler, which is the closest thing Hawaii offers to a longer, gentler shallot season.
- Exposure: windward slopes catch frequent showers, while leeward sides can go long stretches with little rain.
The usual starting logic for a cool-season allium in the tropics is to begin in the cooler part of your local year and aim to finish harvest before your wettest or hottest stretch. This page does not have a county-tested set of planting months to hand you, and a made-up range would be worse than none. Variety matters too, since some shallots cope with mild winters and short, even days better than others. The guide to the best shallots to grow in Hawaii covers that side, and the overview of growing shallots in Hawaii covers the rest of the season.
What will not work here
Start with the most common mistake: following a mainland calendar. Advice like “plant as soon as the soil can be worked, four to six weeks before the last frost” has nothing to anchor to in Hawaii. There is no last frost. A gardener who waits for a cold snap to signal the start of the season will wait indefinitely, and one who plants on a mainland date will be working to a clock that has nothing to do with local conditions.
Overwintering fails for the same reason. The mainland routine of planting in fall, mulching heavily and letting the crop sit dormant through freezing weather rests on a dormant season that lowland Hawaii does not have. With the coldest month still averaging a 66.8°F nightly low in Honolulu, shallots in the ground do not shut down. They keep growing, and they keep drawing pests and disease pressure. A planting made “for winter” and left unattended becomes a standing crop in a warm, active garden.
Wet windward gardens defeat close spacing. Shallots form clusters, and packing them tight leaves little air movement around the necks and lower leaves. On a windward slope where showers arrive in any month, that trapped dampness invites rot in the bulb and fungal trouble on the foliage. Raised rows or mounded beds, wider spacing and fast-draining soil do more good there than any date. A bulb that sits in saturated ground at the end of its cycle will rot before it cures, whatever month you planted it.
The opposite garden fails differently. On a dry leeward coast, a once-a-week soak is the standard mistake. Shallots have shallow roots, so a weekly watering schedule leaves them swinging between drought and flood, which stunts bulbs and can push plants to bolt. Smaller, more frequent watering, drip lines and mulch work better there. Mulch is also one of the few tools that cools bare soil in full tropical sun.
Last, picking by name alone fails. Varieties bred for a cold-winter, long-day climate may not form good bulbs under the shorter, steadier days of the islands. That does not mean they cannot be grown, only that the label’s “plant by” date means little. Treat any outside variety as an experiment in a small trial row before you commit a whole bed.
What changes across Hawaii
Hawaii is not one garden. The USDA Plant Hardiness Zone Map (2023 edition, built on 1991-2020 normals) places the state across zones 9a to 13a. That is an enormous spread for a single state, and it means there is no single answer to “when to plant.” The zone system rests on one variable, the average annual extreme minimum temperature, so it describes how cold the coldest night gets and says nothing about rainfall, wind or day length. Honolulu is the reference city for the figures on this page. Other parts of the state differ, sometimes a great deal.
If you garden at altitude
Higher ground runs cooler. For a shallot grower, that usually stretches the growing period and softens the heat stress that hits lowland beds, which is why elevation is the biggest lever you have. It also means a lowland suggestion may be early or late for you, and a planting that works at sea level may need adjusting upslope. The summits that see frost are far above any ordinary garden, so frost protection is still not part of the planning.
If you garden on the windward or north-facing side
Gardens on the wetter, windward sides of the islands, including many north-facing slopes, get more frequent rain. Plan around drainage first and date second. Aim to have your bulbs maturing during the driest part of your own local year rather than copying a leeward neighbor’s schedule. Two gardens on the same island can be on opposite wet and dry timetables.
Do not assume your zone from this page or from the island you live on. Look up your own location on the USDA Plant Hardiness Zone Map and read the zone for your ZIP code there. If your result is at the cooler end of the range, you are likely at some elevation, and that should shape how you read every other part of this page.
Where to check this for your own county
The best source for a real planting date is the state’s land-grant extension service. For Hawaii, that is the University of Hawaii CTAHR Extension program. Go there with two specific requests. First, look for the local planting calendar for your county or island, and for any vegetable calendar that lists onions or other bulb alliums, which is the closest published guide to shallot timing. Second, look for the varieties that have been trialled in your county. A trial result from your own conditions tells you far more than a catalog description does.
If you cannot find shallots listed by name, ask an extension office or agent which allium varieties have done well locally and in what months growers put them in. Extension offices and local growers’ groups often know details that never make it into a published sheet, such as which side of the island stays too wet in a given month.
A county recommendation beats a state one. Hawaii covers islands with deserts, rainforests and cool uplands, and one page cannot hold all of that. This page is the state-level view. It gives you the reasoning (no frost, so rainfall, elevation and exposure drive everything) and warns you off the approaches that fail. It does not give a month for your garden, and a local extension answer should override anything here that disagrees with it.
Checking this against your own garden
Your own observations outrank every date on this page. Three are worth watching, and none needs equipment.
- Soil warmth by feel. Push your hand into the bed at planting depth, early in the morning and again in mid-afternoon. If it feels cool and damp at both times, you have a shaded, high or wet spot. If it feels warm and dry by midday, you have a hot, quick-draining one. That tells you how much mulch and watering you will need.
- The first true leaves. Watch how quickly a planted bulb roots and sends up green shoots. Fast, sturdy growth says the spot suits the crop. Slow, yellowish or lopsided growth suggests too much rain, too much heat or poor drainage.
- How long water stays. After a hard rain, note how many hours the bed stays soggy. A bed that stays waterlogged will rot bulbs at the end of the season, however good your timing was.
Keep notes for a season. Write down your planting date, the first leaves, the rainiest weeks and the harvest. After a year you will hold a calendar more accurate than any state-level page, including this one.
Common questions
Is there a frost date for planting shallots in Hawaii?
No. NOAA’s 1991-2020 normals show zero days per year at or below 32°F at the Honolulu station, and no freeze occurs in inhabited areas. Frost happens only on the high summits, such as Mauna Kea, Mauna Loa and Haleakala.
Do I need a cold winter to grow shallots here?
Honolulu’s coldest month still has a mean daily minimum of 66.8°F, so lowland gardens do not get a mainland-style winter. Higher elevations run cooler. Variety choice and local trial results matter more than waiting for cold.
What is my hardiness zone in Hawaii?
The USDA map places Hawaii in zones 9a to 13a, so there is no single answer for the state. Check the USDA Plant Hardiness Zone Map using your own ZIP code, since Honolulu is only one reference point.
Where can I find a planting calendar for my county?
Start with the University of Hawaii CTAHR Extension and look for your county’s vegetable or allium planting calendar and its variety trial results. A county recommendation takes priority over this state-level page.