The USDA Zone info is a great tool for gardeners to help us determine your gardening schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

A common way of figuring out when it's a good idea to plant garden cress is to check out the USDA zone info for Boulder.

Planting Calendar for Garden cress

Frost tolerance for garden cress:	Not tolerant of frost.
When to plant:	After the last frost when the weather gets warmer.

Since garden cress are not cold tolerant it is important to wait until after the last frost when the weather gets warmer before you can plant them.

The earliest that you can plant garden cress in Boulder is April. However, you really should wait until May if you don't want to take any chances.

The last month that you can plant garden cress and expect a good harvest is probably August. Any later than that and your garden cress may not have a chance to really do well. You can get started a little bit earlier by starting your garden cress 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.

Keep in mind that USDA zone info for Boulder may not be accurate from year to year and the actual date of last frost will vary from year to year. Since half of the time in Boulder you get surprised by a frost after April 15 be ready to protect your garden cress in the event of a surprise late frost.

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.