One of the first steps you take when you are getting a good idea 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.

By looking at the USDA zone info for Portland it's a good idea to determine when it's the best time to plant blue throatwort.

Planting Calendar for Blue Throatwort

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

Since blue throatwort do not do well in cold weather it is necessary to wait until after the last frost has passed before you can plant them.

The earliest that you can plant blue throatwort in Portland 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 blue throatwort and expect a good harvest is probably September. If you wait any later than that and your blue throatwort may not have a chance to fully mature. If you are starting your blue throatwort indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

The average date of last frost is February 15 in Portland. You can expect an average low temperature of 25°F in the coldest months of winter.

Since the USDA zone info for Portland may not be accurate from year to year the actual date of last frost changes from year to year. Half of the time in Portland you get surprised by a frost after February 15 so just be sure to be ready to cover your blue throatwort if you have a surprise late frost.

USDA Zone Info for Portland

Here is the info for USDA Zone 9b.

Average Date of Last Frost (spring)	February 15
Average Date of First Frost (fall)	December 15
Lowest Expected Low	25°F
Highest Expected Low	30°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 30°F.

Plants to Grow in Portland

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