One of the best tools that you have as gardeners to help us estimate your gardening schedule is the USDA zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

In Rockville you can figure out when it's possible to plant columbine by using the USDA zone info.

Planting Calendar for Columbine

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

Since columbine are one of those plants that can tolerate a little bit of cold weather you can plant them just a bit earlier in the year than more sensitive plants.

The earliest that you can plant columbine in Rockville 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 columbine and expect a good harvest is probably September. If you wait any later than that and your columbine may not have a chance to fully mature. You can get started a couple of weeks earlier by starting your columbine indoors.

Last Frost Date

In Rockville the average date of last frost happens on April 15. It might get as low as 0°F during the coldest months of winter.

Always keep in mind that the actual date of last frost is not always accurate because it is based on the USDA zone info for Rockville and it is different every year. Since half of the time in Rockville it frosts late in the year after April 15 be ready to protect your columbine if you have a late frost.

USDA Zone Info for Rockville

Here is the info for USDA Zone 7a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	0°F
Highest Expected Low	5°F

This means that on a really cold year, the coldest it will get is 0°F. On most years you should be prepared to experience lows near 5°F.

Plants to Grow in Rockville

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