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

A common way of getting a good idea when it's a good idea to plant sorrel is to examine the USDA zone info for Boulder.

Planting Calendar for Sorrel

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

Sorrel do well in mild cold which means that you can plant them a little bit earlier in the year than other plants that might not handle the cold.

The earliest that you can plant sorrel in Boulder 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 sorrel and expect a good harvest is probably September. You probably don't want to wait any later than that or else your sorrel may not have a chance to grow to maturity. You can get started a little bit earlier by starting your sorrel indoors.

Last Frost Date

The average date of last frost is April 15 in Boulder. In the coldest months of winter you can expect an average low temperature of -15°F.

Just be sure to remember that the actual date of last frost is not always accurate because it is based on the USDA zone info for Boulder and it will vary from year to year. Half of the time in Boulder last frost occurs after April 15 so make sure that you are prepared to protect your sorrel in the event of one of those late frosts.

USDA Zone Info for Boulder

Here is the info for USDA Zone 5b.

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

This means that on a really cold year, the coldest it will get is -15°F. On most years you should be prepared to experience lows near -10°F.

Plants to Grow in Boulder

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