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 making a decision about when it's a good idea to plant dipladenia is to use the USDA zone info for Havre.

Planting Calendar for Dipladenia

Frost tolerance for dipladenia:	Not tolerant of frost.
When to plant:	After the last frost.

It's probably not a good idea to plant dipladenia until after the last frost because they are not cold tolerant.

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

Last Frost Date

The average date of last frost is 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 may not be accurate from year to year the actual date of last frost changes from year to year. Since half of the time in Havre last frost occurs after May 15 be ready to cover your dipladenia in the event of one of those late frosts.

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.