One of the best tools that you have as gardeners to help us estimate your gardening schedule is the USDA zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

You will be able to figure out when it's a good idea to plant impatiens by checking out the USDA zone info for Zone 4b.

Planting Calendar for Impatiens

Frost tolerance for impatiens:	Not tolerant of frost.
When to plant:	After the last frost when the weather gets warmer.

Impatiens require warm weather which means that you must wait until it warms up after the last frost has passed before you can plant them.

The earliest that you can plant impatiens in Zone 4b 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 impatiens and expect a good harvest is probably August. If you wait any later than that and your impatiens may not have a chance to fully mature. If you are starting your impatiens indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

On average all chance of frost has passed is on May 15 in Zone 4b. You can expect an average low temperature of -25°F in the coldest months of winter.

Since the USDA zone info for Zone 4b is just an average the actual date of last frost can change quite a bit from year to year. Since half of the time in Zone 4b last frost occurs after May 15 be ready to cover your impatiens in the event of a late frost.

USDA Zone Info for Zone 4b

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 Zone 4b

You may be interested in your other planting guides for Zone 4b.