One of the best tools that you have as gardeners to help us estimate 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.

You should be able to estimate when it's possible to plant broccoli by referring to the USDA zone info for Helena.

Planting Calendar for Broccoli

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

You can plant broccoli just a bit earlier in the year because they are one of those plants that can tolerate a little bit of cold weather.

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

Last Frost Date

On average the last frost when the weather gets warmer is on May 15 in Helena. You should expect an average low temperature of -25°F in the coldest months of winter.

It's important to remember that USDA zone info for Helena may not be accurate from year to year and the actual date of last frost can change quite a bit from year to year. Since half of the time in Helena you get surprised by a frost after May 15 be ready to protect your broccoli if you have a late frost.

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.