One of the best tools that you have as gardeners to help us estimate your gardening schedule is the USDA zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

You can determine when you can plant zinnia in Rapid City by looking at the USDA zone info.

Planting Calendar for Zinnia

Frost tolerance for zinnia:	Not tolerant of frost.
When to plant:	After the last frost has passed.

You really shouldn't plant zinnia until after all chance of frost has passed because they do not do well in cold weather.

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

Last Frost Date

In Rapid City the average date of last frost happens on April 15. In the coldest months of winter you should expect an average low temperature of -20°F.

Just be sure to remember that the actual date of last frost is just an average because it is based on the USDA zone info for Rapid City and it can change quite a bit from year to year. Since half of the time in Rapid City there is a last frost after April 15 be ready to protect your zinnia in the event of one of those late frosts.

USDA Zone Info for Rapid City

Here is the info for USDA Zone 5a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-20°F
Highest Expected Low	-15°F

This means that on a really cold year, the coldest it will get is -20°F. On most years you should be prepared to experience lows near -15°F.

Plants to Grow in Rapid City

You may be interested in your other planting guides for Rapid City.