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.

The first opportunity to plant dahlia in Portland can be determined by checking out the USDA zone info.

Planting Calendar for Dahlia

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

Since dahlia are not cold tolerant it is important to wait until after all chance of frost has passed before you can plant them.

The earliest that you can plant dahlia 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 dahlia and expect a good harvest is probably August. If you wait any later than that and your dahlia may not have a chance to really do well. Starting your dahlia indoors is a great way to get them started a few weeks earlier.

Last Frost Date

In Portland the average date of last frost happens on April 15. It might get as low as -15°F during 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 is different every year. Since half of the time in Portland you get surprised by a frost after April 15 be ready to protect your dahlia if you have a late frost.

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.