One of the first steps you take when you are making a decision about 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.

It's a good idea to figure out when you can plant tree onions by looking at the USDA zone info for Lake Oswego.

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.

Tree onions do well in mild cold which tells us that you can plant them just a tiny bit earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant tree onions in Lake Oswego 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. Any later than that and your tree onions may not have a chance to fully mature. Starting your tree onions indoors is a great way to get them started a little bit earlier.

Last Frost Date

In Lake Oswego the average date of last frost happens on March 15. In the coldest months of winter you can expect an average low temperature of 15°F.

Remember that the actual date of last frost may not be accurate from year to year because it is based on the USDA zone info for Lake Oswego and it changes from year to year. Since half of the time in Lake Oswego it frosts late in the year after March 15 be ready to cover your tree onions in the event of a late frost.

USDA Zone Info for Lake Oswego

Here is the info for USDA Zone 8b.

Average Date of Last Frost (spring)	March 15
Average Date of First Frost (fall)	November 15
Lowest Expected Low	15°F
Highest Expected Low	20°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 20°F.

Plants to Grow in Lake Oswego

You may be interested in your other planting guides for Lake Oswego.