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

By using the USDA zone info for Riverdale you should be able to determine when it's the best time to plant purple rock cress.

Planting Calendar for Purple Rock Cress

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

You can plant purple rock cress quite a bit earlier in the year because they do well in cold.

The earliest that you can plant purple rock cress in Riverdale 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 purple rock cress and expect a good harvest is probably September. If you wait any later than that and your purple rock cress may not have a chance to fully mature. If you are starting your purple rock cress indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

On average all chance of frost has passed is on April 15 in Riverdale. You should expect an average low temperature of -10°F in the coldest months of winter.

Since the USDA zone info for Riverdale may not be accurate from year to year the actual date of last frost changes from year to year. Since half of the time in Riverdale you get surprised by a frost after April 15 be ready to protect your purple rock cress if you have one of those late frosts.

USDA Zone Info for Riverdale

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 Riverdale

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