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Ontario tomatoes wait for the May long weekend, and so should you

Published · Written for a southern Ontario garden

Short answer

In southern Ontario, plant tomatoes outside from the Victoria Day long weekend until mid-June, and start seeds indoors from early March to early April. The last frost around Toronto is usually in early May, but tomatoes also need warm nights. Ripe fruit comes from late July until mid-October.

Tomato sowing calendar

From the VegLog crop library. Change the frost dates to match your garden.

Last frost around 4 May, first frost around 13 October.

Sow indoors
early March to early April
Plant out
mid-May to mid-June
Harvest
late July to mid-October

Spacing, depth and good neighbours for tomato

In southern Ontario, tomatoes go out on or after the Victoria Day long weekend in late May. That’s the tradition, and it’s a good one. The last frost around Toronto is usually in early May, but tomatoes also need warm soil and nights above 10 °C (50 °F), and those take a couple more weeks to arrive.

You can plant until mid-June. Start seeds indoors from early March to early April.

These dates are for Toronto and southern Ontario, with a last frost around May 4 and a first frost around October 13. North of the GTA, in Ottawa or cottage country, add a week or two in spring and expect frost sooner in fall.

Starting seeds

  1. Sow seeds 0.5 cm (¼ in) deep in seed-starting mix, from early to mid-March.
  2. Keep them warm, around 21 to 27 °C (70 to 80 °F), until they come up.
  3. Grow them under a light, 5 to 8 cm (2 to 3 in) above the plants, for 14 to 16 hours a day.
  4. Move each seedling into a 10 cm (4 in) pot when it has its first true leaves, burying the stem up to the seed leaves.

Garden centres have good transplants from early May if you’d rather skip this step.

Hardening off

Indoor plants need a week to get used to sun and wind. Put them outside in a sheltered, shady spot for an hour or two, then a little longer each day with more sun. Bring them in if a cold night is forecast.

Planting out

  1. Choose the sunniest spot you have. Tomatoes need at least eight hours of sun.
  2. Space plants 45 cm (18 in) apart, in rows 60 cm (2 ft) apart.
  3. Plant deep, burying the stem up to the top few leaves. Roots grow all along it.
  4. Put in a stake or cage at the same time.
  5. Water well, and mulch once the soil is warm.

Basil, marigolds and carrots grow well nearby. Keep tomatoes away from potatoes and sweet corn.

Through the summer

Water deeply two or three times a week, and more in a July heat wave. Even watering prevents blossom end rot and split fruit. Feed every week or two with a tomato fertilizer once the first fruit forms.

On staked, tall varieties, pinch out the side shoots that grow where a leaf meets the stem. Determinate, bushy varieties need no pinching and suit a short Ontario season well.

Harvest

The first ripe tomatoes come about 55 to 85 days after planting out, usually from late July. In late September, pinch off new flowers and small fruit so the plant ripens what’s left. Pick everything before the first frost in mid-October.

Common problems

Early blight and septoria leaf spot. Brown spots on the lower leaves, spreading upward. Remove affected leaves, mulch to stop soil splashing and water at the base.

Blossom end rot. Black, sunken patches on the fruit. Water evenly.

Cold nights. Purple-tinged leaves in early June mean the plant is cold. It’ll recover as nights warm.

Choose southern Ontario on the tomato page for the full calendar. A zone 5 garden in the northern US runs on almost the same dates: see tomatoes in zone 5.

Questions people also ask

Can I plant tomatoes before Victoria Day in Ontario?

Around Toronto, the last frost is usually in early May, so a week or two earlier can work in a warm year. But nights below 10 °C (50 °F) stall growth, so early plants rarely ripen fruit much sooner. Cover them if you take the chance.

When should I start tomato seeds in Ontario?

From early March to early April, about six to eight weeks before planting out. Mid-March is a good target for a Victoria Day planting.

How do I ripen green tomatoes before frost?

In late September, pinch off new flowers so the plant ripens the fruit it has. Before the first frost, pick full-sized green tomatoes and ripen them indoors at room temperature.

Dates set to your own frost dates

VegLog works out sowing and planting times for your town, then reminds you when each job is due.

Keep reading

When to plant

Canberra tomatoes go in after Melbourne Cup Day, and not before

In Canberra, plant tomatoes out from Melbourne Cup Day in early November to mid-December, once the frost risk has passed. Sow seed indoors from early September to early October. Tomatoes ripen from late January and keep coming until the first autumn frosts in April.

When to plant

Labour Day tomatoes? In Christchurch, give them a few more weeks

Labour Weekend in late October is New Zealand's traditional tomato planting date, and it suits Auckland and the north. In Christchurch and Canterbury, frosts can come until late October, so plant out from mid-November or protect early plants. Sow seed indoors in September. Fruit ripens from January to April.

When to plant

When it's safe to plant tomatoes outside, zone by zone

Plant tomatoes outside about two weeks after your last spring frost, when nights stay above 50 °F. That's mid-April to early May in zones 7 and 8, early to mid-May in zones 5 and 6, and late May to June in zone 4. Start seeds indoors six to eight weeks before planting out.

Let VegLog keep track of the dates

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