One of the best tools that you have as gardeners to help us estimate your gardening schedule is the 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.

By looking at the USDA zone info for Boulder you will be able to estimate when it's the best time to plant lysimachia.

Planting Calendar for Lysimachia

Frost tolerance for lysimachia:	Tolerant of some frost.
When to plant:	Up to 5 weeks before last frost.

You can plant lysimachia a little bit earlier in the year because they are moderately cold tolerant.

The earliest that you can plant lysimachia 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 lysimachia and expect a good harvest is probably September. You probably don't want to wait any later than that or else your lysimachia may not have a chance to really do well. Starting your lysimachia indoors is a great way to get them started a little bit earlier.

Last Frost Date

In Boulder the average date of last frost happens on April 15. It might get as low as -15°F during the coldest months of winter.

Remember that the actual date of last frost is just an average because it is based on the USDA zone info for Boulder and it will vary 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 lysimachia 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.