The USDA Zone info is a great tool for gardeners to help us estimate your gardening schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

The first chance to plant pennyroyal in Houghton should be estimated by reviewing 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 tells us that you can get them planted much earlier than other frost tender plants.

The earliest that you can plant pennyroyal in Houghton is February. However, you really should wait until March if you don't want to take any chances.

The last month that you can plant pennyroyal and expect a good harvest is probably September. Any later than that and your pennyroyal may not have a chance to fully mature. You can get started a little bit earlier by starting your pennyroyal indoors.

Last Frost Date

On average the last frost has passed is on April 15 in Houghton. In the coldest months of winter you should expect an average low temperature of -15°F.

Since the USDA zone info for Houghton is just an average the actual date of last frost will vary from year to year. Since half of the time in Houghton there is a last frost after April 15 be ready to protect your pennyroyal in the event of a late frost.

USDA Zone Info for Houghton

Here is the info for USDA Zone 5b.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-15°F
Highest Expected Low	-10°F

This means that on a really cold year, the coldest it will get is -15°F. On most years you should be prepared to experience lows near -10°F.

Plants to Grow in Houghton

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