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

In Zone 1b you can figure out when it's the best time to plant pennyroyal by looking at the USDA zone info.

Planting Calendar for Pennyroyal

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

Pennyroyal are very cold tolerant which means that you can start planting them much earlier than other plants that might not handle the cold.

The earliest that you can plant pennyroyal in Zone 1b 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 pennyroyal and expect a good harvest is probably July. Any later than that and your pennyroyal may not have a chance to really do well. You can get started a couple of weeks earlier by starting your pennyroyal indoors.

Last Frost Date

In Zone 1b the average date of last frost happens on June 15. You can expect an average low temperature of -55°F in the coldest months of winter.

Since the USDA zone info for Zone 1b 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 1b there is a last frost after June 15 be ready to cover your pennyroyal if you have one of those late frosts.

USDA Zone Info for Zone 1b

Here is the info for USDA Zone 1b.

Average Date of Last Frost (spring)	June 15
Average Date of First Frost (fall)	July 15
Lowest Expected Low	-55°F
Highest Expected Low	-50°F

This means that on a really cold year, the coldest it will get is -55°F. On most years you should be prepared to experience lows near -50°F.

Plants to Grow in Zone 1b

You may be interested in your other planting guides for Zone 1b.