London in September: what to plant
Over the last 5 years, September in London has run 12.2–20.2°C with about 77 mm of rain across the month. Here is what weather like that will carry to harvest.
Everything above is a five-year average. In the game it is this — the weather London is actually having, today.
Grow one in London's weather right now →❄️ No sub-zero nights in September in the last 5 years — frost is not the limiting factor here.
🗓️ This month sits inside the frost-free window. Average last spring frost around Mar 9, first autumn frost around Nov 21 — roughly 257 frost-free days. Sow tender crops after the last frost date and make sure they finish before the first.
☀️ About 8.7 h of sunshine a day this month. Within the month it cools by about 4.6°C from the first ten days to the last — the window for autumn sowings is opening.
Sow this month — when would you harvest?
Assuming you sow in mid-September, then adding up the warmth London usually gets, one day at a time — which is why some of these run past the end of the month.
| Crop | Days | Harvest around |
|---|---|---|
| 🌿 Garlic chives | 217 | Apr 19 |
| 🥕 Parsnip | 231 | May 3 |
| 🧅 Onion | 245 | May 17 |
| 🥬 Napa cabbage | 206 | Apr 8 |
| 🧅 Leek | 231 | May 3 |
⏳ Too late this month: Zucchini, Green Beans, Amaranth greens, Marigold, Potato, Cauliflower, Strawberry would still be in the ground when the first frost arrives (around Nov 21). Sow them earlier in the year, or grow them under cover.
🌡️ Chili Pepper, Yardlong bean, Bitter melon, Luffa, Winter melon, Aubergine, Okra never accumulate enough heat outdoors in London — not in any month. Locally these need a greenhouse or a warm windowsill.
Best crops to sow now
They are all ideal for this month — the only real difference is how long each one takes, so pick whatever you want to eat.
- 🥒 Zucchini about 105 days to harvest Recent mean 16.2°C — right in the sweet spot
- 🥢 Green Beans about 97 days to harvest Recent mean 16.2°C — right in the sweet spot
- 🌿 Amaranth greens about 89 days to harvest Recent mean 16.2°C — right in the sweet spot
- 🏵️ Marigold about 66 days to harvest Recent mean 16.2°C — right in the sweet spot
- 🥔 Potato about 98 days to harvest Recent mean 16.2°C — right in the sweet spot
- 🌿 Garlic chives about 76 days to harvest Recent mean 16.2°C — right in the sweet spot
- 🥕 Parsnip about 105 days to harvest Recent mean 16.2°C — right in the sweet spot
- 🧅 Onion about 94 days to harvest Recent mean 16.2°C — right in the sweet spot
- 🥬 Cauliflower about 78 days to harvest Recent mean 16.2°C — right in the sweet spot
- 🥬 Napa cabbage about 70 days to harvest Recent mean 16.2°C — right in the sweet spot
- 🍓 Strawberry about 62 days to harvest Recent mean 16.2°C — right in the sweet spot
- 🧅 Leek about 95 days to harvest Recent mean 16.2°C — right in the sweet spot
Leave these for another month
- 🌶️ Okra — Recent mean 16.2°C is too cold (ideal 20–33°C)
- 🍆 Aubergine — Recent mean 16.2°C is too cold (ideal 18–32°C)
- 🍈 Winter melon — Recent mean 16.2°C is too cold (ideal 18–32°C)
Other months in London
📍 Somewhere else? Look up your own city →
Temperature and rainfall come from Open-Meteo's historical observations for London, averaged day by day over the last 5 years. Whether a crop finishes in time is worked out from its own starting temperature and heat requirement — those numbers are listed on each crop page if you want to check them.