One of the first steps you take when you are figuring out 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 first opportunity to plant hardy hibiscus in Boulder can be figured out by using the USDA zone info.

Planting Calendar for Hardy Hibiscus

Frost tolerance for hardy hibiscus:	Very tolerant of frost.
When to plant:	Up to 7 weeks before last frost.

Since hardy hibiscus are very cold tolerant you can plant them much earlier in the year than other frost tender plants.

The earliest that you can plant hardy hibiscus 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 hardy hibiscus and expect a good harvest is probably September. Any later than that and your hardy hibiscus may not have a chance to fully mature. Starting your hardy hibiscus indoors is a great way to get them started a little bit earlier.

Last Frost Date

The average date of last frost is April 15 in Boulder. It might get as low as -15°F during the coldest months of winter.

Keep in mind that USDA zone info for Boulder is just an average and the actual date of last frost is different every year. Since half of the time in Boulder it frosts late in the year after April 15 be ready to protect your hardy hibiscus 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.