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.

One way of getting a good idea when it's possible to plant bok choi is to consult the USDA zone info for Helena.

Planting Calendar for Bok Choi

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

Bok Choi are one of those plants that can tolerate a little bit of cold weather which tells us that you can get them planted earlier than other plants that might not handle the cold.

The earliest that you can plant bok choi 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 bok choi and expect a good harvest is probably August. Any later than that and your bok choi may not have a chance to fully mature. If you are starting your bok choi indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

In Helena the average date of last frost happens on May 15. In the coldest months of winter you can expect an average low temperature of -25°F.

Always keep in mind that the actual date of last frost is an average because it is based on the USDA zone info for Helena and it will vary from year to year. Half of the time in Helena you get a frost after May 15 so be sure to be ready to cover your bok choi 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.