Ontario · Growing Zone 6b
Gardeners in Markham, ON can expect the average last spring frost around April 17, and the first fall frost around October 31, based on historical Environment Canada frost data for the area. That gives Markham a frost-free growing season of roughly 197 days. Actual frost dates shift by a week or two year to year, so use this as a planning baseline rather than an exact guarantee, and always check your local forecast before moving tender plants outside.
You have your Markham frost dates. Now put them to work: GrowBlock counts back your indoor seed-starting weeks, marks your safe planting day, warns you before a frost, and lays your whole season out on one timeline.
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Most warm-season crops (tomatoes, peppers, squash) need transplanting only after the last frost has passed, and are usually started indoors 6 to 8 weeks before that date. Cold-hardy crops (peas, lettuce, spinach) can often go in the ground a few weeks before the last frost. As Markham's first fall frost approaches in October, it's time to plan the last harvests for anything frost-sensitive still in the ground.
Approximate dates for common crops in Markham, worked out from the local last frost around April 17. Warm crops go out after frost, cold-hardy crops a few weeks before it, and anything with an indoor start is counted back from its sow date.
| Crop | Start indoors | Sow / transplant out | Approx. harvest |
|---|---|---|---|
| 🍅 Tomato | March 13 | May 1 | July 20 |
| 🌶️ Pepper | February 27 | May 1 | July 15 |
| 🥒 Cucumber | — | April 24 | June 21 |
| 🥬 Zucchini | — | April 24 | June 13 |
| 🥬 Lettuce | — | March 27 | May 11 |
| 🥬 Spinach | — | March 27 | May 14 |
| 🫛 Peas | — | March 27 | May 28 |
| 🥕 Carrots | — | March 27 | June 3 |
| 🫘 Bush beans | — | April 17 | June 6 |
| 🥬 Kale | February 27 | March 27 | May 21 |
Guideline dates from Markham's average frost window, not a guarantee. GrowBlock tunes these to each variety you plant and adjusts as you build your beds.
This calendar is a starting point. In GrowBlock every date is tuned to the exact varieties you plant and updates as you lay out your beds, and you can share the plan with whoever you garden with, changes show up for both of you.
Build your Markham garden planAround April 17 on average, though it can vary by a week or two either way depending on the year.
Markham is in zone 6b, with a frost-free season of about 197 days.
Now that you have your dates, here is how to put them to work through the season:
More how-to on the GrowBlock gardening blog.
See frost dates for all Canadian cities covered by GrowBlock.