One of the best tools that you have as gardeners to help us figure out your gardening schedule is the USDA zone info. 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 alternanthera in Portland can be determined by reviewing the USDA zone info.

Planting Calendar for Alternanthera

Frost tolerance for alternanthera:	Not tolerant of frost.
When to plant:	After the last frost when the weather gets warmer.

Since alternanthera are not cold tolerant you must wait until after the last frost has passed before you can plant them.

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

Last Frost Date

On average the last frost has passed is on 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 is just an average the actual date of last frost is different every year. Since half of the time in Portland there is a last frost after February 15 be ready to protect your alternanthera 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.