Before planting it is a good idea to find your USDA Zone info to estimate your garden schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

A way of figuring out when it's the best time to plant helianthemum is to refer to the USDA zone info for Washington.

Planting Calendar for Helianthemum

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

Helianthemum are moderately cold tolerant which means that you can plant them earlier than plants that are more sensitive to the cold.

The earliest that you can plant helianthemum in Washington 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 really do well. Starting your helianthemum indoors is a great way to get them started a little bit earlier.

Last Frost Date

The average date of last frost is March 15 in Washington. You should expect an average low temperature of 10°F in the coldest months of winter.

Remember that USDA zone info for Washington is just an average and the actual date of last frost can change quite a bit from year to year. Half of the time in Washington there is a last frost after March 15 so make sure that you are ready to protect your helianthemum if you have one of those late frosts.

USDA Zone Info for Washington

Here is the info for USDA Zone 8a.

Average Date of Last Frost (spring)	March 15
Average Date of First Frost (fall)	November 15
Lowest Expected Low	10°F
Highest Expected Low	15°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 15°F.

Plants to Grow in Washington

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