One of the first steps you take when you are making a decision about your gardening schedule is find your USDA Zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

A way of estimating when it's the best time to plant torenia is to examine the USDA zone info for Boulder.

Planting Calendar for Torenia

Frost tolerance for torenia:	Not tolerant of frost.
When to plant:	After the last frost.

Torenia do not do well in cold weather which tells us that it's necessary to wait until it warms up after the last frost has passed before you can plant them.

The earliest that you can plant torenia 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 torenia and expect a good harvest is probably August. Any later than that and your torenia may not have a chance to fully mature. If you are starting your torenia indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

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

Since the USDA zone info for Boulder is not always accurate the actual date of last frost is different every year. Since half of the time in Boulder there is a last frost after April 15 be ready to protect your torenia 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.