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.

By referring to the USDA zone info for Worthington you should be able to figure out when it's the best time to plant primula.

Planting Calendar for Primula

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

You can plant primula quite a bit earlier in the year because they are very cold tolerant.

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

The last month that you can plant primula and expect a good harvest is probably August. You probably don't want to wait any later than that or else your primula may not have a chance to grow to maturity. If you are starting your primula indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

The average date of last frost is May 15 in Worthington. In the coldest months of winter you should expect an average low temperature of -25°F.

Since the USDA zone info for Worthington is not always accurate the actual date of last frost can change quite a bit from year to year. Half of the time in Worthington you get surprised by a frost after May 15 so just be sure to be ready to cover your primula if you have a surprise late frost.

USDA Zone Info for Worthington

Here is the info for USDA Zone 4b.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-25°F
Highest Expected Low	-20°F

This means that on a really cold year, the coldest it will get is -25°F. On most years you should be prepared to experience lows near -20°F.

Plants to Grow in Worthington

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