The USDA Zone info is a great tool for gardeners to help us estimate your gardening schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The first opportunity to plant zinnia in Havre can be figured out by referring to the USDA zone info.

Planting Calendar for Zinnia

Frost tolerance for zinnia:	Not tolerant of frost.
When to plant:	After the last frost has passed.

Zinnia are not cold tolerant which means that you must wait until it warms up after the last frost when the weather gets warmer before you can plant them.

The earliest that you can plant zinnia in Havre is May. However, you really should wait until June if you don't want to take any chances.

The last month that you can plant zinnia and expect a good harvest is probably August. If you wait any later than that and your zinnia may not have a chance to grow to maturity. If you are starting your zinnia indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

On average the last frost when the weather gets warmer is on May 15 in Havre. It might get as low as -30°F during the coldest months of winter.

Since the USDA zone info for Havre is not always accurate the actual date of last frost is different every year. Since half of the time in Havre you get a frost after May 15 be ready to protect your zinnia if you have a late frost.

USDA Zone Info for Havre

Here is the info for USDA Zone 4a.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-30°F
Highest Expected Low	-25°F

This means that on a really cold year, the coldest it will get is -30°F. On most years you should be prepared to experience lows near -25°F.

Plants to Grow in Havre

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