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

A common way of estimating when it's possible to plant centaurea is to refer to the USDA zone info for Ripon.

Planting Calendar for Centaurea

Frost tolerance for centaurea:	Tolerant of some frost.
When to plant:	Up to 5 weeks before last frost.

Centaurea are moderately cold tolerant which means that you can plant them earlier than other frost tender plants.

The earliest that you can plant centaurea in Ripon 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 centaurea and expect a good harvest is probably September. Any later than that and your centaurea may not have a chance to grow to maturity. You can get started a little bit earlier by starting your centaurea indoors.

Last Frost Date

In Ripon the average date of last frost happens on April 15. You should expect an average low temperature of -20°F in the coldest months of winter.

Since the USDA zone info for Ripon is an average the actual date of last frost can change quite a bit from year to year. Since half of the time in Ripon you get surprised by a frost after April 15 be ready to protect your centaurea if you have one of those late frosts.

USDA Zone Info for Ripon

Here is the info for USDA Zone 5a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-20°F
Highest Expected Low	-15°F

This means that on a really cold year, the coldest it will get is -20°F. On most years you should be prepared to experience lows near -15°F.

Plants to Grow in Ripon

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