One of the first steps you take when you are estimating your gardening schedule is find your USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The earliest that you can plant anchusa in Zone 4b can be figured out by referring to the USDA zone info.

Planting Calendar for Anchusa

Frost tolerance for anchusa:	Very tolerant of frost.
When to plant:	Up to 7 weeks before last frost.

Anchusa do ok in quite a bit of cold which tells us that you can plant them quite a bit earlier in the year than more sensitive plants.

The earliest that you can plant anchusa in Zone 4b 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 anchusa and expect a good harvest is probably August. If you wait any later than that and your anchusa may not have a chance to really do well. You can get started a few weeks earlier by starting your anchusa indoors.

Last Frost Date

The average date of last frost is May 15 in Zone 4b. You should expect an average low temperature of -25°F in the coldest months of winter.

Since the USDA zone info for Zone 4b is not always accurate the actual date of last frost can change quite a bit from year to year. Half of the time in Zone 4b last frost occurs after May 15 so make sure that you are prepared to cover your anchusa in the event of a surprise 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.