Before planting it is a good idea to find your USDA Zone info to figure out your garden schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

A common way of making a decision about when it's possible to plant zinnia is to refer to the USDA zone info for Tucson.

Planting Calendar for Zinnia

Frost tolerance for zinnia:	Not tolerant of frost.
When to plant:	After the last frost.

Zinnia require warm weather which means that you really should wait until it warms up after the last frost has passed before you can plant them.

The earliest that you can plant zinnia in Tucson is March. However, you really should wait until April if you don't want to take any chances.

The last month that you can plant zinnia and expect a good harvest is probably September. You probably don't want to wait any later than that or else your zinnia may not have a chance to fully mature. If you are starting your zinnia indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

In Tucson 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.

It's important to remember that the actual date of last frost is an average because it is based on the USDA zone info for Tucson and it changes from year to year. Half of the time in Tucson last frost occurs after February 15 so always be ready to cover your zinnia if you have a late frost.

USDA Zone Info for Tucson

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 Tucson

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