One of the first steps you take when you are making a decision about your gardening schedule is find your 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.

You will be able to figure out when to plant asters by looking at the USDA zone info for Zone 4a.

Planting Calendar for Asters

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

Since asters do well in moderate cold you can plant them a bit earlier in the year than other frost tender plants.

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

It's important to remember that USDA zone info for Zone 4a is an average and the actual date of last frost will vary from year to year. Half of the time in Zone 4a there is a last frost after May 15 so be sure to be ready to protect your asters if you have one of those late frosts.

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.