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.

It's a good idea to estimate when it's possible to plant sweet peas by looking at the USDA zone info for Boulder.

Planting Calendar for Sweet Peas

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

Sweet Peas are barely cold tolerant which tells us that you can get them planted just a bit earlier than other frost tender plants.

The earliest that you can plant sweet peas in Boulder 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 sweet peas and expect a good harvest is probably August. If you wait any later than that and your sweet peas may not have a chance to fully mature. Starting your sweet peas indoors is a great way to get them started a little bit earlier.

Last Frost Date

On average the last frost has passed is on April 15 in Boulder. It might get as low as -15°F during the coldest months of winter.

Since the USDA zone info for Boulder is an average the actual date of last frost is different every year. Since half of the time in Boulder last frost occurs after April 15 be ready to cover your sweet peas if you have 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.