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

One way of getting a good idea when it's the best time to plant tree onions is to use the USDA zone info for Oregon.

Planting Calendar for Tree onions

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

Since tree onions are one of those plants that can tolerate a tiny bit of cold weather you can plant them a bit earlier in the year than plants that are more sensitive to the cold.

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

Last Frost Date

The average date of last frost is April 15 in Oregon. In the coldest months of winter you should expect an average low temperature of -20°F.

It's important to remember that USDA zone info for Oregon is not always accurate and the actual date of last frost can change quite a bit from year to year. Since half of the time in Oregon you get surprised by a frost after April 15 be ready to protect your tree onions if you have one of those late frosts.

USDA Zone Info for Oregon

Here is the info for USDA Zone 5a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-20°F
Highest Expected Low	-15°F

This means that on a really cold year, the coldest it will get is -20°F. On most years you should be prepared to experience lows near -15°F.

Plants to Grow in Oregon

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