When to Plant 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.

You can figure out when to plant asters in Ottawa by referring to the USDA zone info.

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Planting Calendar for Asters

Frost tolerance for asters: Tolerant of some frost.
When to plant: Up to 5 weeks before last frost.

Asters do ok in a little bit of cold which tells us that you can plant them a little earlier in the year than plants that are more sensitive to the cold.

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

The earliest that you can plant asters 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 asters and expect a good harvest is probably September. If you wait any later than that and your asters may not have a chance to grow to maturity. If you are starting your 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.

Just be sure to 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 you get a frost after April 15 be ready to cover your asters 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.