Before planting it is a good idea to find your USDA Zone info to figure out 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.

You should be able to estimate when it's a good idea to plant gladiolus by referring to the USDA zone info for Portland.

Planting Calendar for Gladiolus

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

Gladiolus are barely cold tolerant which means that you can start planting them slightly earlier than more sensitive plants.

The earliest that you can plant gladiolus 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 gladiolus and expect a good harvest is probably August. Any later than that and your gladiolus may not have a chance to fully mature. Starting your gladiolus indoors is a great way to get them started a couple of weeks earlier.

Last Frost Date

The average date of last frost is April 15 in Portland. It might get as low as 0°F during the coldest months of winter.

Keep in mind that the actual date of last frost is an average because it is based on the USDA zone info for Portland and it will vary from year to year. Half of the time in Portland last frost occurs after April 15 so make sure that you are prepared to cover your gladiolus in the event of one of those late frosts.

USDA Zone Info for Portland

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 Portland

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