Ontario Planting Calendar: When to Plant by Region

📅 Ontario’s Planting Window Shifts Six Weeks From South to North

The right time to plant in Ontario depends entirely on where in the province you garden. Windsor gardeners can set out tomatoes in mid-May while growers around Sudbury are still weeks from their last frost — a swing of six weeks or more across a province that spans hardiness zones 2a through 7a. A single “Ontario planting date” doesn’t exist, which is why this calendar splits the province into three growing regions and gives real dates for each.

Whether you start your own seeds indoors or buy transplants from a garden centre, this calendar covers both paths — and covers vegetables, herbs, and flowers. Each regional section lists when to start seeds indoors, when to set plants out (grown from seed or store-bought), and when to sow seed straight into the ground. Find your region below, read across your crop’s row, and adjust for your own yard using the microclimate notes further down.

Ontario Frost Dates & Growing Regions

Your frost dates are the anchor every planting date hangs on. The table below groups Ontario’s cities into three regions by their frost-free window, using Environment Canada climate normals and the Government of Ontario’s climate-zone data. Last-frost and first-frost dates are averages at roughly a 50% probability — frost can still land after the spring date or before the fall one, so tender crops always want a few days’ margin.

Read every table below in three columns. Start Seeds Indoors is for growing from seed under lights; Transplant Out is when to set plants into the garden, whether you raised them or bought them; Direct Sow is when to put seed straight into garden soil. A dash (—) means that method isn’t recommended for the crop. For the framework behind counting these dates back from your own frost date, see our complete planting calendar, and for indoor technique, our guide to starting seeds indoors.

Southern Ontario Planting Calendar

Southern Ontario has the province’s longest and most forgiving season, with the last spring frost from late April to early May and a first fall frost that often holds off to mid-to-late October. Windsor and Essex County run about two weeks ahead of the Toronto and London core; near the Great Lakes, trust the earlier end of every window. The dates below reflect the GTA-to-Niagara band.

When to Plant Vegetables in Southern Ontario

When to Plant Herbs in Southern Ontario

When to Plant Flowers in Southern Ontario

The Great Lakes are Southern Ontario’s hidden advantage. Gardens near Lake Ontario, Lake Erie, and the Niagara shoreline get a buffered spring and a stretched-out fall, so a lakeside plot in Prince Edward County or the Niagara fruit belt often plants earlier and harvests later than an inland town at the same latitude. Because the season is long here, this is the one region where slow heat-lovers like peppers, eggplant, and melons reliably finish before frost — and where a spring crop can be followed by a full fall planting.

Eastern & Central Ontario Planting Calendar

Eastern and Central Ontario — the Ottawa Valley, the Kingston and Belleville lakeshore, the Kawarthas, and Peterborough — runs about a week behind the south, with the last spring frost landing early to mid May and the first fall frost arriving late September into early October. Winters here are colder (Zones 5a–6a) even where summers feel similar. Kingston and Prince Edward County, moderated by Lake Ontario, run a touch earlier than the inland Ottawa Valley.

When to Plant Vegetables in Eastern & Central Ontario

When to Plant Herbs in Eastern & Central Ontario

When to Plant Flowers in Eastern & Central Ontario

The Ottawa Valley’s defining feature is cold-air pooling: clear, still nights in spring and fall can drop valley-bottom gardens several degrees below the official reading, so keep row cover on hand into early June for tender transplants. Along the Kingston–Belleville lakeshore and through Prince Edward County, the lake buys extra frost-free days, and that milder pocket is where the region’s longer-season crops do best. With a first frost that can arrive by late September, time fall crops off your first frost date and start them in mid-to-late July rather than August.

Northern Ontario Planting Calendar

In Northern Ontario — North Bay, Sudbury, Thunder Bay, Timmins and beyond — the short season is the whole game. The last spring frost runs mid-May to early June (Sudbury averages around May 27–31), and the first fall frost can return by mid-September, leaving as few as 100 frost-free days. That makes two moves non-negotiable: start every heat-loving crop indoors, and choose short-season, early-maturing varieties so they finish before frost.

When to Plant Vegetables in Northern Ontario

When to Plant Herbs in Northern Ontario

When to Plant Flowers in Northern Ontario

The northern advantage is the long summer day. Once the season finally opens in June, extended daylight drives fast, vigorous growth, and cool-season crops — peas, kale, cabbage, root vegetables — are outstanding here, often sweeter than the same crops grown in a hot southern summer. Cold-frame and row-cover season extension is standard equipment, not a luxury: a few degrees of protection at each end can add the two or three weeks that let a tomato ripen. Frost pockets and elevation matter even more up north, so track your own yard and lean on the later end of every window until you know your ground.

Adjusting for Your Local Microclimate

Regional averages get you close, but your own yard can run two weeks warmer or colder than the nearest weather station. Three local features shift your effective planting dates more than anything else — find yours below and adjust accordingly.

Ontario Fall Planting Calendar

A second planting in mid-summer is what separates a good Ontario garden from a great one, and the timing is driven by your first fall frost rather than your spring one. Count back each crop’s days to maturity from that first frost, then add about two weeks because growth slows as daylight shortens. Because the first frost arrives weeks earlier in the north, the fall-sowing window closes sooner there — the table below gives the practical start dates by region.

Fall Vegetables by Region

Kale, spinach, lettuce, radishes, and Asian greens are the most reliable fall producers, and several — kale especially — turn sweeter after a light frost. Cilantro and dill are the two herbs worth a late-summer sowing: both bolt in summer heat but give a clean fall cutting when sown into cooling August soil. Alongside the fall crop, use succession sowing through the season — sow a short row of a fast crop like radishes, lettuce, arugula, or bush beans, then another every two to three weeks, so the harvest arrives steadily instead of all at once.

Fall-Sown Flower Seeds for Next Year

Flowers work differently in fall: you’re not sowing for autumn bloom — there isn’t enough season left — you’re sowing hardy annuals and perennials that need winter cold to germinate, so they sprout on their own first thing next spring. Sow these in late fall, just before the ground freezes, so the seed chills over winter but doesn’t sprout early. The timing barely varies by region — wait until hard frost is close.

Row covers and cold frames extend both ends of the calendar and effectively move a cold-region garden a zone warmer; for the hardiest cold-season choices, see our guide to the best winter vegetables, and once you’re growing open-pollinated varieties, you can save your own seed for next year.

Ontario Planting Calendar FAQ

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