One of the best tools that you have as gardeners to help us determine your gardening schedule is the USDA zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

It's possible to figure out when to plant onions by referring to the USDA zone info for London.

Planting Calendar for Onions

Frost tolerance for onions:	Very tolerant of frost.
When to plant:	Up to 7 weeks before last frost.

Onions are very cold tolerant which tells us that you can get them planted much earlier than other plants that might not handle the cold.

The earliest that you can plant onions in London is February. However, you really should wait until March if you don't want to take any chances.

The last month that you can plant onions and expect a good harvest is probably September. Any later than that and your onions may not have a chance to fully mature. Starting your onions indoors is a great way to get them started a few weeks earlier.

Last Frost Date

In London the average date of last frost happens on April 15. It might get as low as -10°F during the coldest months of winter.

Remember that the actual date of last frost is just an average because it is based on the USDA zone info for London and it can change quite a bit from year to year. Half of the time in London there is a last frost after April 15 so always be ready to protect your onions if you have one of those late frosts.

USDA Zone Info for London

Here is the info for USDA Zone 6a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-10°F
Highest Expected Low	-5°F

This means that on a really cold year, the coldest it will get is -10°F. On most years you should be prepared to experience lows near -5°F.

Plants to Grow in London

You may be interested in your other planting guides for London.