One of the best tools that you have as gardeners to help us figure out 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 making a decision about when it's possible to plant arabis is to examine the USDA zone info for Zone 4a.

Planting Calendar for Arabis

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

Arabis do well in quite a bit of cold which means that you can plant them quite a bit earlier in the year than more sensitive plants.

The earliest that you can plant arabis in Zone 4a 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 arabis and expect a good harvest is probably August. If you wait any later than that and your arabis may not have a chance to grow to maturity. You can get started a few weeks earlier by starting your arabis indoors.

Last Frost Date

In Zone 4a the average date of last frost happens on May 15. You can expect an average low temperature of -30°F in the coldest months of winter.

Since the USDA zone info for Zone 4a may not be accurate from year to year the actual date of last frost is different every year. Half of the time in Zone 4a it frosts late in the year after May 15 so always be ready to protect your arabis if you have a surprise late frost.

USDA Zone Info for Zone 4a

Here is the info for USDA Zone 4a.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-30°F
Highest Expected Low	-25°F

This means that on a really cold year, the coldest it will get is -30°F. On most years you should be prepared to experience lows near -25°F.

Plants to Grow in Zone 4a

You may be interested in your other planting guides for Zone 4a.