Before planting it is a good idea to find your USDA Zone info to determine your garden schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

You will be able to estimate when it's possible to plant trailing portulaca by looking at the USDA zone info for Helena.

Planting Calendar for Trailing Portulaca

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

You really shouldn't plant trailing portulaca until after the last frost when the weather gets warmer because they require warm weather.

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

Last Frost Date

In Helena the average date of last frost happens on March 15. You should expect an average low temperature of 10°F in the coldest months of winter.

Just be sure to remember that USDA zone info for Helena may not be accurate from year to year and the actual date of last frost can change quite a bit from year to year. Since half of the time in Helena it frosts late in the year after March 15 be ready to protect your trailing portulaca if you have a surprise late frost.

USDA Zone Info for Helena

Here is the info for USDA Zone 8a.

Average Date of Last Frost (spring)	March 15
Average Date of First Frost (fall)	November 15
Lowest Expected Low	10°F
Highest Expected Low	15°F

This means that on a really cold year, the coldest it will get is 10°F. On most years you should be prepared to experience lows near 15°F.

Plants to Grow in Helena

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