The USDA Zone info is a great tool for gardeners to help us estimate your gardening schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

You should be able to estimate when it's a good idea to plant periwinkles by using the USDA zone info for Gaithersburg.

Planting Calendar for Periwinkles

Frost tolerance for periwinkles:	Not tolerant of frost.
When to plant:	After the last frost when the weather gets warmer.

Periwinkles are not cold tolerant which tells us that you have to wait until it warms up after the last frost has passed before you can plant them.

The earliest that you can plant periwinkles in Gaithersburg 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 periwinkles and expect a good harvest is probably August. Any later than that and your periwinkles may not have a chance to really do well. If you are starting your periwinkles indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

In Gaithersburg the average date of last frost happens on April 15. In the coldest months of winter you can expect an average low temperature of 0°F.

Remember that the actual date of last frost is not always accurate because it is based on the USDA zone info for Gaithersburg and it is different every year. Half of the time in Gaithersburg last frost occurs after April 15 so just be sure to be ready to cover your periwinkles in the event of a surprise late frost.

USDA Zone Info for Gaithersburg

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 Gaithersburg

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