One of the first steps you take when you are estimating your gardening schedule is find your 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 USDA zone info for Calistoga should be looked at to figure out when it's possible 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 ok in moderate cold which means that you can get them planted just a bit earlier than plants that are more sensitive to the cold.

The earliest that you can plant tree onions in Calistoga 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 couple of weeks earlier by starting your tree onions indoors.

Last Frost Date

In Calistoga the average date of last frost happens on February 15. It might get as low as 20°F during the coldest months of winter.

Just be sure to remember that the actual date of last frost is an average because it is based on the USDA zone info for Calistoga and it changes from year to year. Half of the time in Calistoga it frosts late in the year after February 15 so make sure that you are ready to cover your tree onions in the event of one of those late frosts.

USDA Zone Info for Calistoga

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 Calistoga

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