One of the best tools that you have as gardeners to help us estimate your gardening schedule is the 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.

In Boston you can figure out when it's possible to plant sweet williams by referring to the USDA zone info.

Planting Calendar for Sweet Williams

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

Since sweet williams are moderately cold tolerant you can plant them a bit earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant sweet williams in Boston 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 sweet williams and expect a good harvest is probably September. You probably don't want to wait any later than that or else your sweet williams may not have a chance to really do well. You can get started a little bit earlier by starting your sweet williams indoors.

Last Frost Date

In Boston the average date of last frost happens on April 15. It might get as low as -5°F during the coldest months of winter.

Always keep in mind that USDA zone info for Boston is an average and the actual date of last frost will vary from year to year. Since half of the time in Boston you get a frost after April 15 be ready to protect your sweet williams if you have a late frost.

USDA Zone Info for Boston

Here is the info for USDA Zone 6b.

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

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

Plants to Grow in Boston

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