For most Idaho gardens, the best shallots are bulb-grown types (sets that multiply into clusters) rather than seed-grown ones, planted as early as the soil allows. Fall planting comes first where winters permit it. Seed types need a longer runway than much of the state offers. The type you choose matters more than the cultivar name, and this page has no county trial data to rank individual cultivars.
The short answer for Idaho
Pick bulb-grown shallots and get them in the ground early: in fall where the winter allows overwintering, or the moment the soil is workable in spring. Treat seed-grown shallots as an option for low, warm valleys only. That is the whole decision, and it comes from the length of the season, not from a favorite flavor or color.
The numbers behind it come from the Boise reference station, a low valley and one of the milder spots in the state. NOAA’s 1991-2020 Climate Normals put the last spring frost between April 23 and May 7, and the first fall frost between October 7 and October 21. Those are probability bands, not calendar promises: the dates between which the chance of a 32F freeze runs from 30 to 70 percent. Line up matching ends of the two bands and you get roughly 167 days between freezes. That is a comfortable window for a shallot, which wants months rather than weeks to size up a bulb.
The same station puts the mean daily minimum of the coldest month at 25.4F. That is an average of nights, not a record low, but it tells you winters here are cold enough to matter and mild enough that a fall-planted set at Boise’s elevation can usually get through with mulch. Higher up, the picture changes, as the third section explains.
| Type | Best fit in Idaho | Main risk |
|---|---|---|
| Bulb-grown, planted in fall | Low valleys and mid-elevations with mulch; the longest growing season of any option | Winter heaving and cold snaps in the higher, colder areas |
| Bulb-grown, planted in early spring | Almost everywhere, and the safer choice at altitude or in the north | A late start if the soil stays cold and wet |
| Seed-grown | Low, long-season valleys, started indoors early | Too little season in most of the state; slower to reach full size |
Within bulb-grown types, look for descriptions that mention good storage and reliable clustering, and ask your county extension office which cultivars have actually been trialed locally. This page does not have variety trial results for Idaho, so it will not pretend to rank named cultivars. For the broader picture of how shallots behave in the state, see Growing Shallots in Idaho, and for timing details, When to Plant Shallots in Idaho.
What will not work here
Seed-grown shallots started late in a cold part of the state are the most common failure. The Boise figures already assume a gentle site. The caution attached to those frost dates is blunt: most of Idaho is higher and colder, with far shorter seasons. If the valley floor gives you about 167 days between freezes, a mountain valley may give you a good deal less, and a slow type that needs nearly all of the longer window has no margin left. You get thin, small bulbs that never fully cure.
Waiting for May is the second trap. Gardeners used to tomatoes and peppers sometimes hold shallots until the last spring frost has surely passed. But the Boise band runs to May 7, and shallots do not need to wait for it. Sets tolerate light frosts. Every week of cool-weather growth you give up in spring is a week of bulb sizing you do not get back, because bulbing is triggered later by warmth and lengthening days. Plant late and the plant has less leaf to feed the bulb when that signal arrives.
Fall planting without protection fails in the colder zones. A coldest-month minimum of 25.4F at Boise says nothing about a site hundreds of feet higher, or in the northern panhandle, where winters run colder and snow cover is less predictable. Bare, unmulched sets heave out of the ground in freeze-thaw cycles, and the exposed bulbs dry out or freeze solid. Mulch is cheap insurance. In the coldest areas, spring planting of sets is simply the safer call.
Summer is the other side of the ledger. This page does not carry rainfall or summer temperature figures for Idaho, so it cannot give you a watering schedule. What it can say is that shallots are shallow-rooted, and much of the state’s gardening is irrigated rather than rain-fed. A once-a-week deep soak that works for a tomato can leave shallots stressed in light, fast-draining soil during a hot dry stretch. Stressed plants bolt more readily and size up poorly. Watch the soil, not the calendar, and check the shallow top few inches of the bed.
Finally, Boise’s dates do not travel. A dated recommendation built on one valley station tells a gardener at higher elevation almost nothing about when freeze danger ends. The honest use of those numbers is as an anchor: your own dates are later in spring and earlier in fall.
What changes across Idaho
The USDA Plant Hardiness Zone Map (2023 edition, built on 1991-2020 normals) lists Idaho as running from zone 3b to 7b. That is four full zones, and on the USDA scale each zone is a 10F step in average annual extreme minimum temperature. The map uses that one variable only. It says nothing about summer heat, season length or moisture, so it tells you whether a plant survives winter, not whether it finishes in time.
With a spread that wide, there is no single answer for Idaho. The lowest valleys sit at one end of the range and the high country at the other, and a shallot recommendation that suits one will be wrong for the other. Which zone you are in depends on your site, so look up your own location on the USDA map rather than assuming from a neighbor’s garden or a nursery tag.
What you shift depends on which direction you are moving from the Boise reference. In the north or at altitude, lean harder toward bulb-grown sets and skip seed-grown types unless you have a greenhouse and a long head start. Plant in fall earlier than a valley gardener would, so roots can establish before the ground freezes, and mulch more heavily once it does. Or skip fall entirely and plant sets the first week the soil can be worked. Expect your last spring freeze to land after the band at Boise, and your first fall freeze before it.
Closer to the low, warmer end of the range, you have more freedom. Fall planting is more forgiving, and seed-grown types become a realistic experiment. Even there, microclimate matters: a cold-air pocket at the bottom of a slope can behave like a different zone from a south-facing bed fifty feet away.
Where to check this for your own county
University of Idaho Extension is the place to go next. The land-grant university runs county offices across the state, and their staff know local frost dates, soil quirks and what has actually grown in your county. This page is the state-level view, and a county recommendation beats a state one every time, because Idaho covers too many climates for one set of dates to hold.
When you get there, look for two things. First, a local planting calendar for onions, garlic and other alliums, since shallots are usually timed alongside them. Second, any variety trial results or recommended lists for your county, which will tell you which cultivars have been grown under conditions like yours. If a shallot-specific calendar does not exist, an onion or garlic calendar for your county is a sound proxy, though you should confirm with the office.
This page does not have an Idaho-specific extension calendar for shallots in hand, and it will not substitute one from another state. Calendars published elsewhere reflect other frost dates and other crops, and borrowing them is how people end up planting a month off. Call or email the county office if the website is thin. Extension staff field exactly these questions, and the answer for your zip code is worth more than anything printed here.
Checking this against your own garden
Your own observations outrank every date on this page. Three are worth watching, and none needs equipment beyond your hands and eyes.
- Soil warmth by feel. Push a hand into the bed in early spring. If the soil still aches cold and clumps wet, wait a few days. If it crumbles and feels merely cool, it is ready for sets. Compare a sunny bed with a shaded one and you learn how much your microclimate runs behind or ahead of the state numbers.
- First green shoots. Note the day the first true leaves push up from fall-planted sets or early-spring ones. If they arrive weeks after a neighbor’s, you are in a colder pocket and should plant earlier next fall.
- The first flower stalks. A shallot sending up a flower stalk is bolting. If it happens early and to many plants, the plants likely went through a cold snap followed by heat, or ran dry. Adjust planting date or watering the next season.
Keep a short note each year with those three dates. After two or three seasons you will have a calendar more accurate than any station’s normals, because it reflects your actual soil, slope and wind.
Common questions
Can I grow shallots from seed in Idaho?
It is possible in the lowest, longest-season valleys if you start seed indoors early, but it is the riskiest route. With about 167 days between freezes even at Boise, and shorter seasons elsewhere, bulb-grown sets give far more reliable results.
Do shallots survive Idaho winters?
Fall-planted sets generally can, especially with mulch, at lower elevations. At Boise the mean daily minimum of the coldest month is 25.4F. In higher and colder areas the risk is greater, and spring planting is safer.
Should I plant in fall or spring?
Fall gives the longest growing season where winters allow it. Spring planting of sets, as soon as the soil is workable, is the better choice at altitude or in the north. The planting calendar covers the timing.
Do the Boise frost dates apply to my county?
Probably not exactly. Boise is a low valley, and most of Idaho is higher and colder, with later last freezes in spring and earlier first freezes in fall. Treat Boise as an anchor and confirm with your county extension office.