Before planting it is a good idea to find your USDA Zone info to determine your garden schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

It's a good idea to estimate when it's the best time to plant periwinkles by reviewing the USDA zone info for Altoona.

Planting Calendar for Periwinkles

Frost tolerance for periwinkles:	Not tolerant of frost.
When to plant:	After the last frost has passed.

You should not plant periwinkles until after all chance of frost has passed because they are not cold tolerant.

The earliest that you can plant periwinkles in Altoona is May. However, you really should wait until June if you don't want to take any chances.

The last month that you can plant periwinkles and expect a good harvest is probably August. Any later than that and your periwinkles may not have a chance to fully mature. You can get started a couple of weeks earlier by starting your periwinkles indoors.

Last Frost Date

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

Just be sure to remember that USDA zone info for Altoona may not be accurate from year to year and the actual date of last frost will vary from year to year. Half of the time in Altoona you get a frost after May 15 so just be sure to be ready to cover your periwinkles in the event of one of those late frosts.

USDA Zone Info for Altoona

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 Altoona

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