One of the first steps you take when you are making a decision about 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.

The best time to plant rock cress in Helena should be determined by referring to the USDA zone info.

Planting Calendar for Rock Cress

Frost tolerance for rock cress:	Very tolerant of frost.
When to plant:	Up to 7 weeks before last frost.

Since rock cress are very cold tolerant you can plant them quite a bit earlier in the year than other frost tender plants.

The earliest that you can plant rock cress in Helena 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 rock cress and expect a good harvest is probably September. If you wait any later than that and your rock cress may not have a chance to grow to maturity. You can get started a little bit earlier by starting your rock cress indoors.

Last Frost Date

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

Remember that the actual date of last frost may not be accurate from year to year because it is based on the USDA zone info for Helena and it can change quite a bit from year to year. Since half of the time in Helena last frost occurs after March 15 be ready to cover your rock cress in the event of one of those late frosts.

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.