Before planting it is a good idea to find your USDA Zone info to figure out your garden schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

One way of making a decision about when it's the best time to plant yarrow is to look at the USDA zone info for Ottawa.

Planting Calendar for Yarrow

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

Yarrow are very cold tolerant which tells us that you can get them planted much earlier than plants that are more sensitive to the cold.

The earliest that you can plant yarrow 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 yarrow and expect a good harvest is probably September. If you wait any later than that and your yarrow may not have a chance to really do well. If you are starting your yarrow indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

In Ottawa the average date of last frost happens on April 15. It might get as low as -10°F during the coldest months of winter.

Remember that the actual date of last frost is not always accurate because it is based on the USDA zone info for Ottawa and it is different every year. Half of the time in Ottawa it frosts late in the year after April 15 so be sure to be ready to cover your yarrow in the event of a 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.