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 estimating when you can plant petunias is to use the USDA zone info for Hermiston.

Planting Calendar for Petunias

Frost tolerance for petunias:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

Petunias do well in some cold which means that you can plant them just a tiny bit earlier in the year than other plants that might not handle the cold.

The earliest that you can plant petunias in Hermiston 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 petunias and expect a good harvest is probably August. Any later than that and your petunias may not have a chance to really do well. You can get started a couple of weeks earlier by starting your petunias indoors.

Last Frost Date

On average the last frost when the weather gets warmer is on April 15 in Hermiston. In the coldest months of winter you can expect an average low temperature of 0°F.

It's important to remember that USDA zone info for Hermiston is an average and the actual date of last frost will vary from year to year. Half of the time in Hermiston you get surprised by a frost after April 15 so always be ready to protect your petunias in the event of one of those late frosts.

USDA Zone Info for Hermiston

Here is the info for USDA Zone 7a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	0°F
Highest Expected Low	5°F

This means that on a really cold year, the coldest it will get is 0°F. On most years you should be prepared to experience lows near 5°F.

Plants to Grow in Hermiston

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