Before planting it is a good idea to find your USDA Zone info to estimate 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 reviewing the USDA zone info for Thornton it's possible to determine when it's a good idea to plant oriental poppies.

Planting Calendar for Oriental poppies

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

Since oriental poppies do well in moderate cold you can plant them a little earlier in the year than other plants that might not handle the cold.

The earliest that you can plant oriental poppies in Thornton 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 oriental poppies and expect a good harvest is probably September. If you wait any later than that and your oriental poppies may not have a chance to grow to maturity. If you are starting your oriental poppies indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

In Thornton the average date of last frost happens on April 15. You can expect an average low temperature of -15°F in the coldest months of winter.

Since the USDA zone info for Thornton is an average the actual date of last frost can change quite a bit from year to year. Since half of the time in Thornton last frost occurs after April 15 be ready to cover your oriental poppies in the event of a surprise 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.