The USDA Zone info is a great tool for gardeners to help us determine your gardening schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The best time to plant calibrachoa in Ottawa should be estimated by looking at the USDA zone info.

Planting Calendar for Calibrachoa

Frost tolerance for calibrachoa:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

Calibrachoa do ok in moderate cold which tells us that you can start planting them slightly earlier than other frost tender plants.

The earliest that you can plant calibrachoa in Ottawa 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 calibrachoa and expect a good harvest is probably August. If you wait any later than that and your calibrachoa may not have a chance to grow to maturity. If you are starting your calibrachoa indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

In Ottawa the average date of last frost happens on April 15. In the coldest months of winter you should expect an average low temperature of -15°F.

Keep in mind that the actual date of last frost is not always accurate because it is based on the USDA zone info for Ottawa and it can change quite a bit from year to year. Half of the time in Ottawa last frost occurs after April 15 so always be ready to protect your calibrachoa in the event of a late frost.

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.