One of the best tools that you have as gardeners to help us estimate 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.

In San Marcos you can estimate when it's possible to plant welsh onion by referring to the USDA zone info.

Planting Calendar for Welsh onion

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

Since welsh onion do ok in moderate cold 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 welsh onion in San Marcos 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 welsh onion and expect a good harvest is probably September. If you wait any later than that and your welsh onion may not have a chance to really do well. You can get started a few weeks earlier by starting your welsh onion indoors.

Last Frost Date

The average date of last frost is January 31 in San Marcos. It might get as low as 30°F during the coldest months of winter.

Since the USDA zone info for San Marcos is not always accurate the actual date of last frost is different every year. Half of the time in San Marcos you get a frost after January 31 so make sure that you are prepared to cover your welsh onion in the event of a surprise late frost.

USDA Zone Info for San Marcos

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 San Marcos

You may be interested in your other planting guides for San Marcos.