When to Plant Helianthemum in Silvis, IL

One of the first steps you take when you are making a decision about your gardening schedule is find your USDA Zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

In Silvis you can determine when you can plant helianthemum by looking at the USDA zone info.

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Planting Calendar for Helianthemum

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

Helianthemum do ok in mild cold which tells us that you can plant them a little bit earlier in the year than other frost tender plants.

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

The earliest that you can plant helianthemum in Silvis 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 helianthemum and expect a good harvest is probably September. You probably don't want to wait any later than that or else your helianthemum may not have a chance to grow to maturity. You can get started a few weeks earlier by starting your helianthemum indoors.

Last Frost Date

On average the last frost when the weather gets warmer is on April 15 in Silvis. It might get as low as -15°F during the coldest months of winter.

Since the USDA zone info for Silvis is just an average the actual date of last frost is different every year. Half of the time in Silvis you get surprised by a frost after April 15 so always be ready to cover your helianthemum if you have a surprise late frost.

USDA Zone Info for Silvis

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 Silvis

You may be interested in your other planting guides for Silvis.