One of the first steps you take when you are making a decision about your gardening schedule is find your USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

You should be able to estimate when you can plant petunias by looking at the USDA zone info for Corvallis.

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 ok in some cold which tells us that you can plant them a bit earlier in the year than other frost tender plants.

The earliest that you can plant petunias in Corvallis 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 few weeks earlier by starting your petunias indoors.

Last Frost Date

The average date of last frost is March 15 in Corvallis. In the coldest months of winter you should expect an average low temperature of 15°F.

It's important to remember that the actual date of last frost is just an average because it is based on the USDA zone info for Corvallis and it is different every year. Half of the time in Corvallis it frosts late in the year after March 15 so make sure that you are prepared to cover your petunias in the event of one of those late frosts.

USDA Zone Info for Corvallis

Here is the info for USDA Zone 8b.

Average Date of Last Frost (spring)	March 15
Average Date of First Frost (fall)	November 15
Lowest Expected Low	15°F
Highest Expected Low	20°F

This means that on a really cold year, the coldest it will get is 15°F. On most years you should be prepared to experience lows near 20°F.

Plants to Grow in Corvallis

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