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.

You will be able to determine when it's the best time to plant delphinium by using the USDA zone info for Riverbank.

Planting Calendar for Delphinium

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

Delphinium are barely cold tolerant which tells us that you can plant them slightly earlier than plants that are more sensitive to the cold.

The earliest that you can plant delphinium in Riverbank 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 delphinium and expect a good harvest is probably September. If you wait any later than that and your delphinium may not have a chance to fully mature. You can get started a few weeks earlier by starting your delphinium indoors.

Last Frost Date

The average date of last frost is February 15 in Riverbank. In the coldest months of winter you should expect an average low temperature of 25°F.

Always keep in mind that the actual date of last frost is an average because it is based on the USDA zone info for Riverbank and it will vary from year to year. Half of the time in Riverbank you get surprised by a frost after February 15 so make sure that you are ready to cover your delphinium if you have one of those late frosts.

USDA Zone Info for Riverbank

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 Riverbank

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