One of the best tools that you have as gardeners to help us estimate your gardening schedule is the 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.

The USDA zone info for Gresham should be read to estimate when it's a good idea to plant zinnia.

Planting Calendar for Zinnia

Frost tolerance for zinnia:	Not tolerant of frost.
When to plant:	After all chance of frost has passed.

Since zinnia are not cold tolerant you really should wait until after all chance of frost has passed before you can plant them.

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

The last month that you can plant zinnia and expect a good harvest is probably August. Any later than that and 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

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

Remember 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 Gresham and it changes from year to year. Half of the time in Gresham you get surprised by a frost after March 15 so make sure that you are prepared to cover your zinnia if you have one of those late frosts.

USDA Zone Info for Gresham

Here is the info for USDA Zone 8b.

Average Date of Last Frost (spring)	March 15
Average Date of First Frost (fall)	November 15
Lowest Expected Low	15°F
Highest Expected Low	20°F

This means that on a really cold year, the coldest it will get is 15°F. On most years you should be prepared to experience lows near 20°F.

Plants to Grow in Gresham

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