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.

You will be able to determine when to plant delphinium by looking at the USDA zone info for Tempe.

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.

Since delphinium are one of those plants that can tolerate a tiny bit of cold weather you can plant them a bit earlier in the year than other frost tender plants.

The earliest that you can plant delphinium in Tempe 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. Any later than that and your delphinium may not have a chance to really do well. Starting your delphinium indoors is a great way to get them started a little bit earlier.

Last Frost Date

On average the last frost is on February 15 in Tempe. You can expect an average low temperature of 25°F in the coldest months of winter.

Remember that USDA zone info for Tempe is not always accurate and the actual date of last frost is different every year. Half of the time in Tempe it frosts late in the year after February 15 so just be sure to be ready to cover your delphinium in the event of a late frost.

USDA Zone Info for Tempe

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 Tempe

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