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.

By referring to the USDA zone info for Boulder it's a good idea to estimate when to plant euphorbia.

Planting Calendar for Euphorbia

Frost tolerance for euphorbia:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

You can plant euphorbia a bit earlier in the year because they do ok in moderate cold.

The earliest that you can plant euphorbia in Boulder is March. However, you really should wait until April if you don't want to take any chances.

The last month that you can plant euphorbia and expect a good harvest is probably August. If you wait any later than that and your euphorbia may not have a chance to fully mature. You can get started a little bit earlier by starting your euphorbia indoors.

Last Frost Date

On average the last frost has passed is on 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 is an average the actual date of last frost is different every year. Since half of the time in Boulder you get surprised by a frost after April 15 be ready to protect your euphorbia 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.