One of the first steps you take when you are making a decision about your gardening schedule is find your USDA Zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

In Bristol you can figure out when it's the best time to plant helianthemum by looking at the USDA zone info.

Planting Calendar for Helianthemum

Frost tolerance for helianthemum:	Tolerant of some frost.
When to plant:	Up to 5 weeks before last frost.

Helianthemum tend to make it in some cold which tells us that you can plant them a bit earlier in the year than other frost tender plants.

The earliest that you can plant helianthemum in Bristol 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 helianthemum and expect a good harvest is probably September. You probably don't want to wait any later than that or else your helianthemum may not have a chance to fully mature. If you are starting your helianthemum indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

On average the last frost is on April 15 in Bristol. In the coldest months of winter you can expect an average low temperature of -10°F.

Since the USDA zone info for Bristol may not be accurate from year to year the actual date of last frost can change quite a bit from year to year. Half of the time in Bristol there is a last frost after April 15 so make sure that you are prepared to protect your helianthemum if you have a late frost.

USDA Zone Info for Bristol

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 Bristol

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