Growing Cilantro in Canada: Succession Sowing for Zones 3–8

Cilantro is one of the most useful herbs in a Canadian kitchen — and one of the most frustrating to grow consistently. The problem is not difficulty; it is timing. Cilantro bolts to seed the moment summer heat arrives, leaving you with flowers and no leaves exactly when you want them most. Succession sowing is the solution, and it works reliably across every Canadian zone from 3 to 8.

This guide covers when to plant cilantro in your zone, how to keep it producing all season, and what to do when the heat rolls in.

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Why Cilantro Bolts — and How Canadian Summers Accelerate It

Cilantro (Coriandrum sativum) is a cool-season herb that treats warm weather as a signal to flower and set seed. Once daytime temperatures consistently exceed 27°C, the plant stops leaf production and shifts all energy toward forming seed heads (coriander seeds). In Canada's short summers, this window arrives fast — even in zone 5b Ottawa or zone 6a Toronto, July and August will reliably trigger bolting.

The good news: cilantro responds perfectly to repeated succession sowing. A fresh sowing every three weeks from early spring through early June, and again from mid-August onward, keeps you in leaves without any single planting surviving the full heat of summer.

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Zone-by-Zone Planting Dates for Cilantro in Canada

Cilantro is direct-sown — it does not transplant well because disturbing the taproot triggers bolting. Always sow directly into the garden or container.

For zones 3–4 (short season): Focus on the spring and early fall windows. Summer heat is brief but intense — skip June–July sowing and resume once August brings cooler nights.

For zones 5–6 (Ontario, Southern Alberta): A late-April first sowing and successions every 3 weeks through early June works well. Resume with an August sowing for a fall harvest.

For zones 7–8 (coastal BC): The longest cilantro window in Canada. Spring sowings can begin in March–April; fall sowings extend into September.

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How to Sow Cilantro Successfully

Crack the seeds first. Cilantro "seeds" are actually two seeds enclosed in a husk. Lightly crush them between your palms or roll them briefly on a hard surface to split the husk — this improves germination rate from around 60% to above 85%.

Sow shallowly. Scatter seeds 1–2 cm apart and cover with no more than 0.5 cm of fine soil or compost. Firm gently.

Keep moist until germination. Cilantro germinates in 7–14 days when soil temperatures are 15–21°C. It struggles to germinate in cold (below 10°C) or hot (above 25°C) soil.

Thin to 5–8 cm spacing. Overcrowded seedlings bolt earlier. Thinning improves airflow and delays flowering.

Direct sow, never transplant. Transplanting cilantro from a pot disturbs the taproot and almost always triggers immediate bolting. Sow where it will grow.

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The Succession Sowing Schedule

Set a reminder every three weeks starting at your first sow date. A simple schedule for a zone 5b garden (Ottawa / Toronto):

• Late April: Sowing 1 — first cool-season batch
• Mid-May: Sowing 2 — overlapping coverage
• Early June: Sowing 3 — last before heat peaks
• Mid-August: Sowing 4 — fall harvest round, as heat breaks
• Early September: Sowing 5 — zone 6 gardeners only; zone 5 may not have enough time

By the time sowing 1 bolts in early June heat, sowing 3 is just leafing out. The fall sowings often produce the most abundant harvest — cooler temperatures slow bolting significantly.

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Harvesting Cilantro

Cut outer leaves first, leaving the inner growing point intact to extend the plant's productive life. Harvest once stems are 10–15 cm tall.

Cut the whole plant when bolting starts. At the first sign of flower stem formation, harvest everything immediately. The leaves are still usable at this stage; once flowers open, the leaf flavour becomes bitter.

Let some plants go to coriander seed. Let one or two plants fully bolt and set seed — you harvest coriander, a completely different spice. Dry the seed heads in a paper bag for a week, then store the seeds. Bonus: some will fall and self-sow for next spring.

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Companion Planting and Location

Cilantro does best in a spot that gets full sun in spring but afternoon shade in July and August — the east side of a taller crop like corn or tomatoes works well. In zones 5–6, a semi-shaded spot genuinely extends the spring harvest by 2–3 weeks.

Cilantro is a good companion for tomatoes and peppers. When allowed to flower, it attracts beneficial insects including parasitic wasps that control aphids and tomato hornworm larvae.

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Saving Cilantro Seed for Next Season

Cilantro self-seeds readily in most Canadian zones. Let one or two plants complete their full cycle: flower, form green seed heads, and dry down to beige-tan. Shake the dry heads into a paper bag and store in a cool, dry place. These seeds (which are also your coriander spice) remain viable for 2–3 years and can be sown next spring.

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Plan Your Cilantro Sowing Schedule

Tracking three to five succession sowings by hand gets complicated. MyGardenPlanner.ca's planting calculator lets you enter your location and zone to get exact sow dates for cilantro and every other crop in your garden — so nothing bolts before you are ready.

Find your cilantro planting dates at mygardenplanner.ca