Before planting it is a good idea to find your USDA Zone info to estimate 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.

You can determine when it's a good idea to plant black radish in Helena by reviewing the USDA zone info.

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 do well in moderate cold which means that you can start planting them earlier than more sensitive plants.

The earliest that you can plant black radish in Helena is March. However, you really should wait until April 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 August. You probably don't want to wait any later than that or else your black radish may not have a chance to grow to maturity. Starting your black radish indoors is a great way to get them started a couple of weeks earlier.

Last Frost Date

On average the last frost when the weather gets warmer is on May 15 in Helena. It might get as low as -25°F during the coldest months of winter.

Since the USDA zone info for Helena is not always accurate the actual date of last frost can change quite a bit from year to year. Since half of the time in Helena it frosts late in the year after May 15 be ready to protect your black radish in the event of one of those late frosts.

USDA Zone Info for Helena

Here is the info for USDA Zone 4b.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-25°F
Highest Expected Low	-20°F

This means that on a really cold year, the coldest it will get is -25°F. On most years you should be prepared to experience lows near -20°F.

Plants to Grow in Helena

You may be interested in your other planting guides for Helena.