Before planting it is a good idea to find your USDA Zone info to estimate your garden schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

By checking out the USDA zone info for London it's possible to estimate when to plant gomphrena.

Planting Calendar for Gomphrena

Frost tolerance for gomphrena:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

Gomphrena do ok in moderate cold which tells us that you can plant them slightly earlier than other frost tender plants.

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

The last month that you can plant gomphrena and expect a good harvest is probably August. Any later than that and your gomphrena may not have a chance to really do well. If you are starting your gomphrena indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

On average the last frost when the weather gets warmer is on April 15 in London. You should expect an average low temperature of -10°F in the coldest months of winter.

Since the USDA zone info for London may not be accurate from year to year the actual date of last frost is different every year. Half of the time in London you get a frost after April 15 so make sure that you are prepared to protect your gomphrena if you have a surprise late frost.

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.