Climate-based cucumber planting guide for London, Ontario
When to Plant Cucumbers in London: Timing and Maturity Guide
Cucumbers are usually straightforward to fit into the season in London. Gardeners generally have room to think about the kind of result they want, not just whether the crop will finish.
Typical Planting Window
Use the planting dates below for cucumbers in London.
Gardeners usually either sow outdoors around May 10 or start indoors around April 12 and transplant outdoors around May 10. Most varieties need about 50–60 days to reach maturity.
Cucumbers are usually very workable in London. The extra room is most useful when gardeners use it to aim for a better finish rather than simply relying on the crop to mature.
Even in a supportive climate, the season only solves the timing side of the problem. The rest still comes down to how the crop is managed.
Best local strategy: Here the strategy is to turn a safe seasonal fit into better production: establish well, keep plants growing, and harvest consistently.
Can Cucumbers Mature in London?
Growing degree days measure how much useful warmth the season provides. For warm-season crops like cucumbers, GDD helps show whether local heat accumulation is usually strong enough for the crop to grow steadily and finish before fall.
From the usual planting window, London typically provides about 2113 growing degree days for cucumbers. With a typical crop target of 800, that leaves a heat margin of +1313. That large heat margin means season length is usually not the limiting issue here. The season usually gives gardeners room to focus on finish quality, harvest goals, and overall crop performance.
GDD Checkpoints for London
If planting later than usual, this table shows how much growing degree day heat is still available from each point in the season. For cucumbers, it is most useful for judging how much freedom you still have to plant for quality, finish, and harvest goals as the season moves along.
| Checkpoint | Remaining GDD | Heat margin | Fit vs typical target |
|---|---|---|---|
| Apr 15 | 2134 | +1334 | Comfortable |
| May 1 | 2133 | +1333 | Comfortable |
| May 15 | 2082 | +1282 | Comfortable |
| Jun 1 | 1927 | +1127 | Comfortable |
| Jun 15 | 1734 | +934 | Comfortable |
| Jul 1 | 1463 | +663 | Comfortable |
Best Cucumber Varieties for London
The season in London usually supports most cucumber varieties comfortably, which means the more useful decision is what kind of crop you want rather than simply how fast it finishes.
Varieties that often fit well here include:
- Cool Breeze — an earlier type that is more forgiving where gardeners want a faster start
- Suyo Long — can be productive in a decent season, especially where warmth arrives on time
- Marketmore 76 — a classic slicing cucumber that often fits reasonably well when planted into warmth
- Spacemaster — compact and relatively approachable where gardeners want fast returns
- Straight Eight — productive and well known, but happier when the season is not especially compressed
- Telegraph — better suited to supportive warmth or protected growing
| Variety class | Typical days to maturity | Typical GDD need | Local fit |
|---|---|---|---|
| Very early | 45–50 | 700 | Good fit |
| Early | 50–55 | 800 | Good fit |
| Mid-season | 55–65 | 900 | Good fit |
| Late | 65–75 | 1000 | Good fit |
Main risk: When this crop disappoints here, the problem is usually practical rather than climatic. Timing, steady growth, and harvest stage matter more than season length.
How Frost Affects Cucumbers in London
London usually has about 166 frost-free days, with a typical last spring frost around May 3 and a typical first fall frost around October 16.
Cucumbers are generally frost-tender and temperatures below about 32°F ( 0 °C) can slow growth or damage plants.
Cucumbers are much more exposed to frost risk, so the frost dates matter as real planting boundaries rather than rough planning markers.
When this crop disappoints in London, the issue is usually management rather than climate fit. Timing, consistency, and harvest decisions matter more than season length.
In London, the local season usually gives cucumbers plenty of breathing room when planting happens around May 10. Local gardens do not all warm and cool at the same pace. For a better local margin, gardeners usually do best in south-facing walls, sheltered gardens, raised beds, and sunnier urban lots. Cooler spots like low spots, exposed sites, and shadier yards often make timing tighter. For cucumbers, the best local sites often help the crop get moving earlier and make timing a little more forgiving.
Related crops
Related crops worth comparing for the same city:
For a broader local overview, see the London planting guide. You can also use the Growing Degree Day Planner to test planting dates and crop timing.