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.

A common way of estimating when you can plant black radish is to examine the USDA zone info for Helena.

Planting Calendar for Black radish

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

Black radish can survive in some cold which means that you can plant them just a bit earlier in the year than more sensitive plants.

The earliest that you can plant black radish 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 black radish and expect a good harvest is probably September. If you wait any later than that and your black radish may not have a chance to fully mature. You can get started a couple of weeks earlier by starting your black radish indoors.

Last Frost Date

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

Always keep in mind 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 changes from year to year. Since half of the time in Helena last frost occurs after March 15 be ready to protect your black radish in the event of a 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.