When should I harvest potatoes in Ontario?

It depends whether you want new potatoes or storage potatoes. New (baby) potatoes are ready once the plants flower — usually July in southern Ontario, a little later further north. Dig gently at the edge of a hill and take what you need; the rest keep growing. Storage potatoes, the main crop, are ready 2–3 weeks after the tops (the green foliage) have naturally died back and yellowed — typically late September into October in southern Ontario, and earlier, from mid-September, in the north where frost arrives sooner. The wait after die-back lets the skins 'set' so the potatoes store for months instead of weeks.

How do I know potatoes are ready to harvest?

For new potatoes, the signal is flowering — when the plants bloom, tubers are egg-sized and sweet underneath. For storage potatoes, wait until the tops die back on their own, then give it 2–3 more weeks and check the skins with the skin-set test: rub a tuber's skin firmly with your thumb. If it stays put, the skins have set and the crop will store. If it rubs or flakes off easily, the potatoes aren't cured on the vine yet — leave them another week or two (as long as frost allows). Set skins are the single difference between potatoes that keep all winter and ones that rot by November.

When are new potatoes ready in Ontario?

New potatoes are ready at flowering, which in most of southern Ontario (Toronto, London, Windsor, Hamilton) falls in July, roughly 7–8 weeks after planting. In eastern and central Ontario (Ottawa, Kingston, Barrie) it's mid-to-late July, and in the north (Sudbury, Thunder Bay) late July into August. You don't have to lift the whole plant — reach in at the side of the hill, take a few tender tubers, and firm the soil back. New potatoes don't store; they're for eating fresh within a few days, which is exactly the point.

Do I have to wait until the potato plants die back?

For a storage crop, yes. The dying-back of the tops is the plant finishing the tubers and hardening their skins. If you dig while the plants are still green and growing, the skins are thin and delicate — those potatoes bruise, and they'll rot in storage within weeks. Once the foliage has yellowed and flopped, stop watering and wait 2–3 weeks, then harvest. The exception is new potatoes for immediate eating, which you take early on purpose. In Ontario the die-back-plus-two-weeks timing usually lands the storage harvest in late September or October, ahead of the ground freezing.

Should I harvest potatoes before the first frost in Ontario?

Frost on the tops doesn't hurt the tubers underground, but you should get storage potatoes out of the ground before a hard, ground-penetrating freeze — a frozen tuber turns to mush. Ontario's first-frost spread is wide: Windsor and the far southwest may not see a killing frost until late October, while northern Ontario (Sudbury, Thunder Bay) can freeze by mid-to-late September. A light frost that kills the tops is actually a useful signal — it triggers skin-set, so wait about two weeks after it, then dig before the ground itself freezes. Never let mature potatoes sit through a hard freeze.

Why are my Ontario potatoes green, and are they safe?

Green skin means the tuber was exposed to light — either growing too close to the surface (not enough hilling) or sitting in the sun after harvest. The green is chlorophyll, but it signals higher levels of solanine, a natural toxin that tastes bitter and can make you ill in quantity. Cut green parts away generously, or discard badly greened potatoes. To prevent it: hill soil up over the plants as they grow, and once dug, move potatoes out of the light immediately — cure and store them in the dark. Potatoes are a dark-storage crop, the opposite of onions and garlic.

How do I cure and store potatoes in Ontario?

Cure first, then store cold. After lifting, let the potatoes cure for 1–2 weeks somewhere dark, humid, and cool-ish (10–15°C) — this toughens the skins and heals small nicks. Don't wash them; brush off loose soil. Then move them to long-term storage: dark, humid, and cold at 4–7°C — an unheated basement, cold room, or root cellar. Never the fridge (too cold — it converts starch to sugar and darkens them when cooked). Keep potatoes away from onions, which give off moisture and gas that spoil each other, and check the bin monthly, removing any that soften. Well-cured Ontario potatoes keep 4–6 months.

What about Colorado potato beetle at harvest time?

Colorado potato beetle is the main potato pest in Ontario, and by harvest the plants may look chewed — that's usually cosmetic if the tubers sized up. The bigger harvest-time job is not carrying problems into next year: don't compost heavily infested vines, remove volunteers, and rotate potatoes to a different bed on a 3–4 year cycle (don't follow potatoes with tomatoes, peppers, or eggplant — they share diseases). Harvest on a dry day, cure in the dark, and start next spring's crop with certified seed potatoes rather than saved grocery-store ones to keep disease out.

ONTARIO HARVEST GUIDE

When to Harvest Potatoes in Ontario — Signs and Timing

When to harvest potatoes in Ontario: dig new potatoes once the plants flower in July, and lift the main storage crop 2–3 weeks after the tops die back, when the skins have set. Regional windows from Windsor to the north, the skin-set test, curing, and dark cold storage.

Updated July 2026 · Harvest windows derived from Ontario frost and planting data

Potatoes give Ontario gardeners two harvests from one planting. The first is new potatoes — tender, thin-skinned tubers you dig at flowering in July, for eating fresh within days. The second is the main storage crop, lifted in fall once the plants have died back and the skins have hardened enough to keep for months.

Getting the storage timing right is what separates potatoes that last until spring from ones that rot by Remembrance Day. And in Ontario, the fall window swings widely — from October in Windsor to mid-September in the north. This guide covers both harvests, the skin-set test, and how to store the crop in the dark.

When to harvest potatoes in Ontario at a glance: dig new potatoes at flowering (July in the south). For storage potatoes, wait until the tops die back, then 2–3 more weeks and confirm with the skin-set test (skin doesn't rub off). Storage harvest: southern Ontario late Sep–Oct · eastern/central late Sep–early Oct · northern Ontario mid–late Sep. Dig before a hard freeze, cure 1–2 weeks in the dark, then store cold (4–7°C), humid, and dark — never in light (green = solanine).

🌿 Planting, not harvesting? See When to Plant Potatoes in Ontario for the spring planting windows by region, and Growing Potatoes in Canada for varieties, hilling, and pest control.

Two Harvests: New Potatoes vs Storage Potatoes

The single most useful thing to understand about harvesting potatoes is that flowering and die-back are two different signals for two different crops:

New potatoes — harvest at flowering. When the plants bloom (July in southern Ontario), the tubers are egg-sized and sweet. Dig a few from the side of a hill and firm the soil back; the plant keeps growing. New potatoes don't store — eat them within days.

Storage potatoes — harvest 2–3 weeks after die-back. When the tops yellow and flop on their own, the plant has finished the tubers. Stop watering, wait 2–3 weeks for the skins to set, then lift the whole crop for winter storage.

The skin-set test confirms a storage crop is ready: rub a tuber's skin firmly with your thumb. If it holds, the skins have set and the potatoes will keep. If it rubs off, wait another week or two — as long as frost allows.

Ontario Potato Harvest Windows — by Region

These windows assume spring planting in the standard window for each region. Ontario's north–south frost spread is wide, so the storage-harvest deadline (before a hard freeze) varies by weeks — always confirm the storage crop with the skin-set test first.

Ontario Region (City)	Zone	New Potatoes	Storage Harvest
Southwest (Windsor, London)	6a–7a	Early–Mid Jul	Late Sep–Oct
Golden Horseshoe (Toronto, Hamilton)	6b	Mid Jul	Late Sep–mid Oct
Eastern Ontario (Ottawa, Kingston)	5a–5b	Mid–Late Jul	Late Sep–early Oct
Central (Barrie, Muskoka)	5a	Mid–Late Jul	Mid–Late Sep
Northern Ontario (Sudbury, Thunder Bay)	3b–4b	Late Jul–Aug	Mid Sep

How to Lift Potatoes Without Damaging Them

A speared or bruised potato won't store, so dig carefully:

Dig from the side. Start a fork or spade well outside the hill (20–25 cm from the stem) and lever inward and up, so you lift under the tubers rather than through them.
Harvest on a dry day when the soil is dry-ish — wet-dug potatoes are muddy, bruise more easily, and store poorly.
Don't wash them. Brush off loose soil by hand; washing shortens storage life. Wash only what you'll eat soon.
Get them out of the light fast. Potatoes left in the sun turn green (solanine) within hours. Move them into the dark to cure right away.
Sort as you go. Set aside any nicked, speared, or green tubers to eat first — only clean, whole potatoes go into long-term storage.

Curing & Storing Potatoes — in the Dark

Potatoes are a dark-storage crop — the opposite of onions and garlic, which cure in airy light. First cure the potatoes for 1–2 weeks somewhere dark, cool-ish (10–15°C), and humid; this toughens the skins and heals small cuts. Don't wash them.

Then move them to long-term storage: dark, humid, and cold at 4–7°C — an unheated Ontario basement, cold room, or root cellar is ideal. Not the fridge (too cold; it turns starch to sugar and the potatoes darken when cooked). Keep potatoes away from onions, don't store them near apples, and check the bin monthly, pulling any that soften. Well-cured storage potatoes keep 4–6 months — right through an Ontario winter.

Common Potato Harvest Mistakes in Ontario

Digging the storage crop too early

Lifting while the plants are still green gives you thin-skinned potatoes that rot in weeks. Wait for die-back, then 2–3 weeks, then the skin-set test.

Leaving them through a hard freeze

Frost on the tops is fine — even helpful for skin-set — but a hard, ground-penetrating freeze turns tubers to mush. Dig before the soil freezes, especially in northern Ontario.

Letting potatoes green in the light

Sun exposure after digging turns skins green with bitter solanine. Move the crop into the dark immediately, and hill soil over the plants during the season to prevent it.

Storing potatoes in the fridge or with onions

The fridge is too cold (sweet, dark-cooking potatoes), and onions and potatoes spoil each other. Store potatoes on their own in a dark, cold, humid room.