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

It's possible to figure out when it's a good idea to plant skullcap by looking at the USDA zone info for Riverside.

Planting Calendar for Skullcap

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

It's a bad idea to plant skullcap until after the last frost because they are not cold tolerant.

The earliest that you can plant skullcap in Riverside 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 fully mature. Starting your skullcap indoors is a great way to get them started a little bit earlier.

Last Frost Date

On average the last frost is on April 15 in Riverside. You can expect an average low temperature of -10°F in the coldest months of winter.

Always keep in mind that the actual date of last frost is not always accurate because it is based on the USDA zone info for Riverside and it will vary from year to year. Half of the time in Riverside you get a frost after April 15 so make sure that you are ready to protect your skullcap in the event of a surprise late frost.

USDA Zone Info for Riverside

Here is the info for USDA Zone 6a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-10°F
Highest Expected Low	-5°F

This means that on a really cold year, the coldest it will get is -10°F. On most years you should be prepared to experience lows near -5°F.

Plants to Grow in Riverside

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