Before planting it is a good idea to find your USDA Zone info to determine your garden schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

You can determine when you can plant arabis in Boulder by checking out the USDA zone info.

Planting Calendar for Arabis

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

Arabis do well in cold which tells us that you can plant them much earlier than more sensitive plants.

The earliest that you can plant arabis 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 arabis and expect a good harvest is probably September. If you wait any later than that and your arabis may not have a chance to really do well. You can get started a couple of weeks earlier by starting your arabis indoors.

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.

Since the USDA zone info for Boulder may not be accurate from year to year the actual date of last frost can change quite a bit from year to year. Since half of the time in Boulder last frost occurs after April 15 be ready to cover your arabis 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.