Before planting it is a good idea to find your USDA Zone info to determine your garden schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

The first chance to plant nierembergia in Portland should be determined by checking out the USDA zone info.

Planting Calendar for Nierembergia

Frost tolerance for nierembergia:	Not tolerant of frost.
When to plant:	After the last frost.

It's probably a bad idea to plant nierembergia until after the last frost when the weather gets warmer because they do not do well in cold weather.

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

The last month that you can plant nierembergia and expect a good harvest is probably August. You probably don't want to wait any later than that or else your nierembergia may not have a chance to grow to maturity. Starting your nierembergia indoors is a great way to get them started a little bit earlier.

Last Frost Date

On average the last frost has passed is on April 15 in Portland. In the coldest months of winter you can expect an average low temperature of -15°F.

Just be sure to remember that USDA zone info for Portland is just an average and the actual date of last frost can change quite a bit from year to year. Half of the time in Portland you get a frost after April 15 so be sure to be ready to cover your nierembergia if you have one of those late frosts.

USDA Zone Info for Portland

Here is the info for USDA Zone 5b.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-15°F
Highest Expected Low	-10°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 -10°F.

Plants to Grow in Portland

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