The USDA Zone info is a great tool for gardeners to help us figure out your gardening schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

It's possible to estimate when you can plant heliotrope by reviewing the USDA zone info for Waltham.

Planting Calendar for Heliotrope

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

You can not plant heliotrope until after the last frost when the weather gets warmer because they require warm weather.

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

Last Frost Date

In Waltham the average date of last frost happens on April 15. You should expect an average low temperature of -10°F in the coldest months of winter.

Since the USDA zone info for Waltham is just an average the actual date of last frost will vary from year to year. Since half of the time in Waltham last frost occurs after April 15 be ready to protect your heliotrope 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.