The USDA Zone info is a great tool for gardeners to help us figure out your gardening schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

You should be able to figure out when to plant skullcap by referring to the USDA zone info for Portland.

Planting Calendar for Skullcap

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

It's not a good idea to plant skullcap until after the last frost has passed because they require warm weather.

The earliest that you can plant skullcap in Portland is April. However, you really should wait until May 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. You probably don't want to wait any later than that or else your skullcap may not have a chance to grow to maturity. You can get started a few weeks earlier by starting your skullcap indoors.

Last Frost Date

On average the last frost when the weather gets warmer is on April 15 in Portland. In the coldest months of winter you should expect an average low temperature of -15°F.

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

USDA Zone Info for Portland

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 Portland

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