The USDA Zone info is a great tool for gardeners to help us determine your gardening schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

A common way of estimating when you can plant larkspur is to use the USDA zone info for Ottawa.

Planting Calendar for Larkspur

Frost tolerance for larkspur:	Very tolerant of frost.
When to plant:	Up to 7 weeks before last frost.

You can plant larkspur much earlier in the year because they do well in cold.

The earliest that you can plant larkspur in Ottawa 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 larkspur and expect a good harvest is probably September. You probably don't want to wait any later than that or else your larkspur may not have a chance to grow to maturity. You can get started a couple of weeks earlier by starting your larkspur indoors.

Last Frost Date

On average the last frost when the weather gets warmer is on April 15 in Ottawa. In the coldest months of winter you can expect an average low temperature of -15°F.

Since the USDA zone info for Ottawa may not be accurate from year to year the actual date of last frost will vary from year to year. Since half of the time in Ottawa it frosts late in the year after April 15 be ready to cover your larkspur in the event of one of those late frosts.

USDA Zone Info for Ottawa

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 Ottawa

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