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.

By reviewing the USDA zone info for Rhinelander you should be able to estimate when you can plant skullcap.

Planting Calendar for Skullcap

Frost tolerance for skullcap:	Not tolerant of frost.
When to plant:	After all chance of frost has passed.

You really shouldn't plant skullcap until after the last frost has passed because they are not cold tolerant.

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

Last Frost Date

The average date of last frost is May 15 in Rhinelander. You should expect an average low temperature of -30°F in the coldest months of winter.

Keep in mind that the actual date of last frost is not always accurate because it is based on the USDA zone info for Rhinelander and it changes from year to year. Half of the time in Rhinelander last frost occurs after May 15 so make sure that you are prepared to protect your skullcap in the event of a late frost.

USDA Zone Info for Rhinelander

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 Rhinelander

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