One of the first steps you take when you are getting a good idea your gardening schedule is find your USDA Zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

You will be able to estimate when it's a good idea to plant calliopsis by using the USDA zone info for Waltham.

Planting Calendar for Calliopsis

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

Calliopsis require warm weather which means that it's necessary to wait until it warms up after the last frost before you can plant them.

The earliest that you can plant calliopsis in Waltham 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 calliopsis and expect a good harvest is probably August. If you wait any later than that and your calliopsis may not have a chance to grow to maturity. If you are starting your calliopsis indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

On average all chance of frost has passed is on April 15 in Waltham. You should expect an average low temperature of -10°F in the coldest months of winter.

Always keep in mind that USDA zone info for Waltham is just an average and the actual date of last frost changes from year to year. Since half of the time in Waltham you get a frost after April 15 be ready to cover your calliopsis if you have one of those late frosts.

USDA Zone Info for Waltham

Here is the info for USDA Zone 6a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-10°F
Highest Expected Low	-5°F

This means that on a really cold year, the coldest it will get is -10°F. On most years you should be prepared to experience lows near -5°F.

Plants to Grow in Waltham

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