Vermont rewards the hardy, patient roots: celeriac, parsnips, salsify, scorzonera, Hamburg parsley, horseradish and Jerusalem artichokes. Tropical tuber crops such as oca and yacon usually lose the race against an October freeze. Burlington’s frost window and the state’s wide hardiness spread explain the split, and the sections below show how to adjust for your own hill, valley or lakeshore.
The short answer for Vermont
Choose roots that tolerate frost and finish on a short clock, or that live underground all winter. That means the taproots and the perennial roots in the table below, plus celeriac if you start it indoors. For the wider picture of how these crops behave in the state, see Growing Unusual Root Crops in Vermont.
The season sets the rules
The reference station is Burlington, which sits on Lake Champlain, the mildest corner of the state. NOAA’s 1991-2020 Climate Normals put the last spring freeze (32°F) between April 30 and May 10, and the first fall freeze between October 3 and October 13. Both ranges come from the 30-70% probability band. they mark the stretch where the chance of a 32°F night is neither remote nor certain. They are odds, not promises, and a cold night inside that window is normal.
The coldest month at Burlington has a mean daily minimum of 12.9°F. That is an average of nightly lows, so individual nights run colder. This page does not carry a summer heat figure for Vermont, so it makes no claim about heat accumulation. What the frost dates do show is a season that is cool and bounded at both ends.
Decision by type
| Type | Examples | Vermont verdict |
|---|---|---|
| Frost-tolerant taproots | Parsnip, salsify, scorzonera, Hamburg parsley | Best bets; cold sweetens them |
| Transplanted long-season root | Celeriac | Good if started indoors |
| Hardy perennial roots and tubers | Jerusalem artichoke, horseradish, burdock | Dependable; plan for spread |
| Frost-tender tropicals | Oca, yacon | Poor odds in the ground |
Timing details for each crop live in When to Plant Unusual Roots in Vermont. Treat the Burlington dates as the generous end of the range.
What will not work here
Tropical tubers run out of season
Oca and yacon are the usual casualties. Both come from the Andes and want a long, frost-free run. Oca in particular puts on its tubers late, as autumn days shorten, which is exactly when a Vermont freeze arrives. At Burlington, the mildest corner of the state, that freeze lands between October 3 and October 13 in the 30-70% band. Frost kills the tops, tuber growth stops, and what you dig is a handful of marbles. In the Green Mountains and the Northeast Kingdom, where the season runs substantially shorter, the result is worse.
Growing them in large pots and hauling the pots indoors before frost is possible. That is a houseplant project, though, not a root bed, and it deserves an honest label.
Early and late mistakes
Setting out celeriac seedlings in late April is a bet against the odds. Between April 30 and May 10, a 32°F night is still a real possibility even at Burlington. A cold snap can stall young celeriac or push it to bolt, and a stalled plant has little time to recover in a short season. Wait until the freeze risk has actually passed in your spot.
Sowing slow roots late fails the other way. A parsnip or salsify sown in midsummer, hoping for a fall crop, has too few weeks before the freeze. These roots need the full spring-to-fall stretch, which is why they go in as early as the soil can be worked.
Soil is the quiet third failure. Stony or heavy ground, common across Vermont, makes long roots fork and stunt, so a deep, loosened bed matters more here than a fancy variety. And roots left in the ground over winter face thaw-and-refreeze cycles in March. Mulch and snow cover help, but a mean coldest-month minimum of 12.9°F means plenty of nights well below that figure. Harvest early in a thaw, not late in the spring.
What changes across Vermont
There is no single answer for the whole state. The USDA Plant Hardiness Zone Map (2023 edition, based on 1991-2020 normals) places Vermont across zones 3b to 5b. That is four half-zone steps inside one state, a wider spread than many people expect from a small place. The system is built on one variable, the average annual extreme minimum temperature, which is a different measure from the 12.9°F coldest-month figure above. Zones describe whether a plant survives winter. They say little about whether it finishes before frost.
Burlington’s frost dates belong to the mild end of that spread. Gardeners in the Green Mountains and the Northeast Kingdom should expect a later last freeze and an earlier first one, and should not apply the Burlington window without adjusting. Exactly how much to adjust is something this page cannot say, because the facts it relies on come from the one lakeshore station.
If you garden in the north or at altitude, shift toward the crops that carry the least season risk. Parsnips, salsify, horseradish and Jerusalem artichokes lean on cold tolerance rather than length of season. Celeriac, the most demanding root on the list, needs an earlier indoor start and a warmer, sheltered spot, or it may simply be the one to drop. Raised beds warm sooner in spring, and a bed on a slope sheds cold air that pools in hollows and frost pockets.
To learn which zone covers your own address, use the USDA map directly and enter your ZIP code. This page will not guess it for you, and neither should a plant tag.
Where to check this for your own county
Your state extension service is the next stop. Start at University of Vermont Extension and look for two things: a planting calendar written for your county, and any varieties that have actually been trialled where you live. Calendars are usually written per crop, so search for the specific root you want rather than a general vegetable chart. Trial results matter even more for unusual roots, since seed catalogs often describe them in generic terms.
A county recommendation beats a state one. Vermont spans lakeshore valleys, river bottoms and high ridges, and a single set of dates cannot serve all of them. This page is the state-level view, built on one reference station and one zone map. It tells you which types of roots fit the state’s season, but it cannot tell you the right week to sow in your town.
Do not assume extension has published a guide for every unusual root. For some, such as salsify or scorzonera, you may find little beyond a general vegetable fact sheet. When that happens, fall back on the nearest equivalent crop (parsnip guidance is a reasonable stand-in for the taproots) and note your own results.
Checking this against your own garden
Your own observations outrank every date here. Three are worth watching, and none needs equipment.
- Soil warmth by feel. Push your hand into the bed in the morning. If it feels cold and clammy, seeds will sit and sulk. A bed that feels cool but workable warms earlier than a neighbor’s shaded one, and that gap is your microclimate speaking.
- The first true leaves. Seedlings first show seed leaves, then the first true leaves with the shape of the adult plant. When parsnip or salsify reach that stage, they have survived germination in your soil. If they arrive weeks later than a friend’s across town, your garden runs cooler, and your calendar should too.
- Where the first frost lands. On the first white morning, note which parts of the yard are frosted and which are clear. Low corners that frost first are the worst places for celeriac and the best places for frost-sweetened parsnips.
Squash planted alongside is a handy indicator as well. When its first male flowers open, the garden has had real warmth. Write the dates down for a year or two, and a notebook will beat any chart.
Common questions
Can I grow celeriac in Vermont?
Yes, with an indoor start and a transplant date after the freeze risk has passed. At Burlington that risk window runs April 30 to May 10, and it stretches later in colder parts of the state.
Can I leave roots in the ground over winter?
Hardy ones such as parsnips, salsify and Jerusalem artichokes can stay put under mulch and snow, and cold improves their flavor. Dig them in a spring thaw before regrowth starts. Winter minimums vary a great deal across Vermont, so test with a few roots first.
Are Burlington’s frost dates my dates?
Probably not. Burlington is the mildest corner of the state, and the Green Mountains and Northeast Kingdom run substantially shorter. Use the Burlington dates as a best case and adjust from your own garden.
Can I grow oca or yacon outdoors?
Rarely with good results. A freeze between October 3 and October 13 at Burlington, and earlier elsewhere, cuts the season short. Containers moved indoors are the realistic route.