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

The first chance to plant portulaca in Helena can be determined by looking at the USDA zone info.

Planting Calendar for Portulaca

Frost tolerance for portulaca:	Not tolerant of frost.
When to plant:	After the last frost.

Since portulaca are not cold tolerant it's necessary to wait until after all chance of frost has passed before you can plant them.

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

Last Frost Date

On average the last frost has passed is on March 15 in Helena. It might get as low as 10°F during the coldest months of winter.

Keep in mind that the actual date of last frost is not always accurate because it is based on the USDA zone info for Helena and it changes from year to year. Since half of the time in Helena there is a last frost after March 15 be ready to cover your 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.