One of the first steps you take when you are determining your gardening schedule is find your USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The USDA zone info for Ottawa can be looked at to figure out when to plant alternanthera.

Planting Calendar for Alternanthera

Frost tolerance for alternanthera:	Not tolerant of frost.
When to plant:	After all chance of frost has passed.

It's probably not a good idea to plant alternanthera until after all chance of frost has passed because they require warm weather.

The earliest that you can plant alternanthera 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 alternanthera and expect a good harvest is probably August. You probably don't want to wait any later than that or else your alternanthera may not have a chance to really do well. If you are starting your alternanthera indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

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

Remember that the actual date of last frost is just an average because it is based on the USDA zone info for Ottawa and it is different every year. Since half of the time in Ottawa there is a last frost after April 15 be ready to cover your alternanthera if you have 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.