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.

You can determine when it's possible to plant marigold in Denver by using the USDA zone info.

Planting Calendar for Marigold

Frost tolerance for marigold:	Not tolerant of frost.
When to plant:	After the last frost has passed.

You really shouldn't plant marigold until after the last frost because they do not do well in cold weather.

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

Last Frost Date

On average the last frost has passed is on April 15 in Denver. In the coldest months of winter you should expect an average low temperature of -15°F.

Since the USDA zone info for Denver may not be accurate from year to year the actual date of last frost changes from year to year. Since half of the time in Denver you get a frost after April 15 be ready to protect your marigold in the event of a late frost.

USDA Zone Info for Denver

Here is the info for USDA Zone 5b.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-15°F
Highest Expected Low	-10°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 -10°F.

Plants to Grow in Denver

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