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.

A common way of determining when it's a good idea to plant trifolium is to look at the USDA zone info for Atherton.

Planting Calendar for Trifolium

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

Since trifolium do ok in moderate cold you can plant them slightly earlier in the year than other frost tender plants.

The earliest that you can plant trifolium in Atherton 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 trifolium and expect a good harvest is probably September. Any later than that and your trifolium may not have a chance to grow to maturity. You can get started a little bit earlier by starting your trifolium indoors.

Last Frost Date

The average date of last frost is February 15 in Atherton. You can expect an average low temperature of 25°F in the coldest months of winter.

Since the USDA zone info for Atherton is an average the actual date of last frost can change quite a bit from year to year. Half of the time in Atherton there is a last frost after February 15 so just be sure to be ready to cover your trifolium in the event of a surprise late frost.

USDA Zone Info for Atherton

Here is the info for USDA Zone 9b.

Average Date of Last Frost (spring)	February 15
Average Date of First Frost (fall)	December 15
Lowest Expected Low	25°F
Highest Expected Low	30°F

This means that on a really cold year, the coldest it will get is 25°F. On most years you should be prepared to experience lows near 30°F.

Plants to Grow in Atherton

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