One of the best tools that you have as gardeners to help us figure out your gardening schedule is the USDA zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

By referring to the USDA zone info for Boulder you should be able to determine when it's possible to plant sweet woodruff.

Planting Calendar for Sweet Woodruff

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

Since sweet woodruff do well in moderate cold you can plant them a little earlier in the year than other frost tender plants.

The earliest that you can plant sweet woodruff 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 sweet woodruff and expect a good harvest is probably September. You probably don't want to wait any later than that or else your sweet woodruff may not have a chance to grow to maturity. If you are starting your sweet woodruff indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

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

Since the USDA zone info for Boulder is just an average the actual date of last frost is different every year. Half of the time in Boulder it frosts late in the year after April 15 so always be ready to cover your sweet woodruff in the event of a 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.