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When to Plant Four-o-clock flower in Thornton, CO

Before planting it is a good idea to find your USDA Zone info to determine your garden schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

By looking at the USDA zone info for Thornton it's a good idea to determine when it's a good idea to plant four-o-clock flower.

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Planting Calendar for Four-o-clock flower

Frost tolerance for four-o-clock flower: Not tolerant of frost.
When to plant: After the last frost.

Four-o-clock flower do not do well in cold weather which means that it is important to wait until it warms up after the last frost has passed before you can plant them.

JanFebMarAprMayJunJulAugSepOctNovDec
Legend 
A good time to plant four-o-clock flower
Possibly ok, but a risky time to plant four-o-clock flower
Probably not a good time to plant four-o-clock flower

The earliest that you can plant four-o-clock flower in Thornton 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 four-o-clock flower and expect a good harvest is probably August. You probably don't want to wait any later than that or else your four-o-clock flower may not have a chance to fully mature. Starting your four-o-clock flower indoors is a great way to get them started a little bit earlier.

Last Frost Date

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

Since the USDA zone info for Thornton may not be accurate from year to year the actual date of last frost can change quite a bit from year to year. Half of the time in Thornton you get a frost after April 15 so make sure that you are ready to cover your four-o-clock flower if you have a late frost.

USDA Zone Info for Thornton

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 Thornton

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