One of the first steps you take when you are determining 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.

By using the USDA zone info for Billings you should be able to determine when it's the best time to plant trailing portulaca.

Planting Calendar for Trailing Portulaca

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

Trailing Portulaca are not cold tolerant which means that it's important to wait until it warms up after the last frost has passed before you can plant them.

The earliest that you can plant trailing portulaca in Billings is May. However, you really should wait until June if you don't want to take any chances.

The last month that you can plant trailing portulaca and expect a good harvest is probably August. Any later than that and your trailing portulaca may not have a chance to grow to maturity. You can get started a couple of weeks earlier by starting your trailing portulaca indoors.

Last Frost Date

The average date of last frost is May 15 in Billings. In the coldest months of winter you can expect an average low temperature of -25°F.

Just be sure to remember that the actual date of last frost is an average because it is based on the USDA zone info for Billings and it can change quite a bit from year to year. Half of the time in Billings there is a last frost after May 15 so just be sure to be ready to cover your trailing portulaca if you have a late frost.

USDA Zone Info for Billings

Here is the info for USDA Zone 4b.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-25°F
Highest Expected Low	-20°F

This means that on a really cold year, the coldest it will get is -25°F. On most years you should be prepared to experience lows near -20°F.

Plants to Grow in Billings

You may be interested in your other planting guides for Billings.