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

The USDA zone info for Longmont can be read to figure out when it's possible to plant cardinal flower.

Planting Calendar for Cardinal Flower

Frost tolerance for cardinal flower:	Not tolerant of frost.
When to plant:	After all chance of frost has passed.

Since cardinal flower are not cold tolerant you need to wait until after the last frost has passed before you can plant them.

The earliest that you can plant cardinal flower in Longmont 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 cardinal flower and expect a good harvest is probably August. Any later than that and your cardinal flower may not have a chance to really do well. Starting your cardinal flower indoors is a great way to get them started a little bit earlier.

Last Frost Date

On average all chance of frost has passed is on April 15 in Longmont. You should expect an average low temperature of -15°F in the coldest months of winter.

Keep in mind that USDA zone info for Longmont is not always accurate and the actual date of last frost is different every year. Half of the time in Longmont you get surprised by a frost after April 15 so make sure that you are prepared to protect your cardinal flower if you have a late frost.

USDA Zone Info for Longmont

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 Longmont

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