One of the best tools that you have as gardeners to help us determine your gardening schedule is the USDA zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The USDA zone info for Del Rio can be reviewed to determine when it's the best time to plant tree onions.

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 a tiny bit of cold which means that 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 Del Rio 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. You probably don't want to wait any later than that or else your tree onions may not have a chance to really do well. You can get started a little bit earlier by starting your tree onions indoors.

Last Frost Date

The average date of last frost is February 15 in Del Rio. You should expect an average low temperature of 20°F in the coldest months of winter.

It's important to remember that USDA zone info for Del Rio is an average and the actual date of last frost is different every year. Half of the time in Del Rio you get surprised by a frost after February 15 so make sure that you are prepared to cover your tree onions in the event of a surprise late frost.

USDA Zone Info for Del Rio

Here is the info for USDA Zone 9a.

Average Date of Last Frost (spring)	February 15
Average Date of First Frost (fall)	December 15
Lowest Expected Low	20°F
Highest Expected Low	25°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 25°F.

Plants to Grow in Del Rio

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