The USDA Zone info is a great tool for gardeners to help us estimate your gardening schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

In Boulder you can determine when you can plant alternanthera by checking out the USDA zone info.

Planting Calendar for Alternanthera

Frost tolerance for alternanthera:	Not tolerant of frost.
When to plant:	After all chance of frost has passed.

Alternanthera are not cold tolerant which means that it's important to wait until it warms up after the last frost when the weather gets warmer before you can plant them.

The earliest that you can plant alternanthera 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 alternanthera and expect a good harvest is probably August. Any later than that and your alternanthera may not have a chance to fully mature. If you are starting your alternanthera indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

In Boulder the average date of last frost happens on April 15. You can expect an average low temperature of -15°F in the coldest months of winter.

Since the USDA zone info for Boulder is just an average the actual date of last frost is different every year. Half of the time in Boulder you get a frost after April 15 so make sure that you are ready to cover your alternanthera 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.