One of the best tools that you have as gardeners to help us figure out your gardening schedule is the USDA zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

A way of estimating when it's possible to plant black radish is to refer to the USDA zone info for Alton.

Planting Calendar for Black radish

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

You can plant black radish a little earlier in the year because they are moderately cold tolerant.

The earliest that you can plant black radish in Alton 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. Any later than that and your black radish may not have a chance to fully mature. If you are starting your black radish indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

On average all chance of frost has passed is on April 15 in Alton. In the coldest months of winter you can expect an average low temperature of -10°F.

Just be sure to 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 Alton and it will vary from year to year. Since half of the time in Alton there is a last frost after April 15 be ready to cover your black radish in the event of a surprise late frost.

USDA Zone Info for Alton

Here is the info for USDA Zone 6a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-10°F
Highest Expected Low	-5°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 -5°F.

Plants to Grow in Alton

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