One of the first steps you take when you are estimating 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 referring to the USDA zone info for Helena you should be able to figure out when it's possible to plant osteospermum.

Planting Calendar for Osteospermum

Frost tolerance for osteospermum:	Tolerant of some frost.
When to plant:	Up to 5 weeks before last frost.

Osteospermum can survive in moderate cold which tells us that you can plant them a little bit earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant osteospermum 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 osteospermum and expect a good harvest is probably September. You probably don't want to wait any later than that or else your osteospermum may not have a chance to really do well. If you are starting your osteospermum indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

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

Since the USDA zone info for Helena may not be accurate from year to year the actual date of last frost changes from year to year. Half of the time in Helena it frosts late in the year after March 15 so just be sure to be ready to protect your osteospermum in the event of 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.