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.

A way of getting a good idea when it's the best time to plant tree onions is to consult the USDA zone info for Del Mar.

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 very little cold which tells us that you can plant them just a tiny bit earlier in the year than other plants that might not handle the cold.

The earliest that you can plant tree onions in Del Mar is February. However, you really should wait until March 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 September. Any later than that and your tree onions may not have a chance to grow to maturity. 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 January 31 in Del Mar. In the coldest months of winter you can expect an average low temperature of 30°F.

Keep in mind that USDA zone info for Del Mar is an average and the actual date of last frost is different every year. Half of the time in Del Mar you get surprised by a frost after January 31 so make sure that you are prepared to protect your tree onions if you have a late frost.

USDA Zone Info for Del Mar

Here is the info for USDA Zone 10a.

Average Date of Last Frost (spring)	January 31
Average Date of First Frost (fall)	December 15
Lowest Expected Low	30°F
Highest Expected Low	35°F

This means that on a really cold year, the coldest it will get is 30°F. On most years you should be prepared to experience lows near 35°F.

Plants to Grow in Del Mar

You may be interested in your other planting guides for Del Mar.