When to Plant Hardy Asters in Ottawa, IL

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

The first chance to plant hardy asters in Ottawa can be determined by checking out the USDA zone info.

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Planting Calendar for Hardy Asters

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

You can plant hardy asters a bit earlier in the year because they do ok in moderate cold.

JanFebMarAprMayJunJulAugSepOctNovDec
Legend 
A good time to plant hardy asters
Possibly ok, but a risky time to plant hardy asters
Probably not a good time to plant hardy asters

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

Last Frost Date

The average date of last frost is April 15 in Ottawa. It might get as low as -15°F during the coldest months of winter.

It's important to remember that USDA zone info for Ottawa is just an average and the actual date of last frost can change quite a bit 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 hardy asters if you have 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.