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.

By reviewing the USDA zone info for Ottawa you will be able to figure out when to plant marigold.

Planting Calendar for Marigold

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

Since marigold are not cold tolerant you need to wait until after the last frost when the weather gets warmer before you can plant them.

The earliest that you can plant marigold in Ottawa 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. Any later than that and your marigold may not have a chance to really do well. You can get started a couple of weeks earlier by starting your marigold indoors.

Last Frost Date

The average date of last frost is April 15 in Ottawa. In the coldest months of winter you can expect an average low temperature of -10°F.

Since the USDA zone info for Ottawa is not always accurate the actual date of last frost is different every year. Half of the time in Ottawa there is a last frost after April 15 so always be ready to protect your marigold in the event of a surprise late frost.

USDA Zone Info for Ottawa

Here is the info for USDA Zone 6a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-10°F
Highest Expected Low	-5°F

This means that on a really cold year, the coldest it will get is -10°F. On most years you should be prepared to experience lows near -5°F.

Plants to Grow in Ottawa

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