One of the first steps you take when you are figuring out 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.

You should be able to figure out when it's the best time to plant iceberg lettuce by looking at the USDA zone info for Riverside.

Planting Calendar for Iceberg lettuce

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

Iceberg lettuce do ok in mild cold which tells us that you can plant them just a tiny bit earlier in the year than more sensitive plants.

The earliest that you can plant iceberg lettuce in Riverside 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 iceberg lettuce and expect a good harvest is probably September. You probably don't want to wait any later than that or else your iceberg lettuce may not have a chance to fully mature. You can get started a little bit earlier by starting your iceberg lettuce indoors.

Last Frost Date

In Riverside the average date of last frost happens on February 15. You should expect an average low temperature of 25°F in the coldest months of winter.

Keep in mind that the actual date of last frost may not be accurate from year to year because it is based on the USDA zone info for Riverside and it can change quite a bit from year to year. Half of the time in Riverside you get surprised by a frost after February 15 so always be ready to protect your iceberg lettuce if you have a surprise late frost.

USDA Zone Info for Riverside

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 Riverside

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