One of the first steps you take when you are determining your gardening schedule is find your USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The earliest that you can plant salpiglossis in Boulder can be figured out by checking out the USDA zone info.

Planting Calendar for Salpiglossis

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

Since salpiglossis are not cold tolerant it's important to wait until after the last frost has passed before you can plant them.

The earliest that you can plant salpiglossis 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 salpiglossis and expect a good harvest is probably August. Any later than that and your salpiglossis may not have a chance to really do well. You can get started a few weeks earlier by starting your salpiglossis indoors.

Last Frost Date

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

Since the USDA zone info for Boulder is not always accurate the actual date of last frost can change quite a bit from year to year. Half of the time in Boulder it frosts late in the year after April 15 so just be sure to be ready to protect your salpiglossis if you have 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.