Before planting it is a good idea to find your USDA Zone info to estimate your garden schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

A common way of getting a good idea when it's possible to plant sweet williams is to examine the USDA zone info for Philadelphia.

Planting Calendar for Sweet Williams

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

You can plant sweet williams a bit earlier in the year because they are one of those plants that can tolerate a little bit of cold weather.

The earliest that you can plant sweet williams in Philadelphia 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. If you wait any later than that and your sweet williams may not have a chance to really do well. Starting your sweet williams indoors is a great way to get them started a few weeks earlier.

Last Frost Date

The average date of last frost is April 15 in Philadelphia. In the coldest months of winter you should expect an average low temperature of 0°F.

Always keep in mind that USDA zone info for Philadelphia is just an average and the actual date of last frost will vary from year to year. Half of the time in Philadelphia last frost occurs after April 15 so just be sure to be ready to cover your sweet williams in the event of a late frost.

USDA Zone Info for Philadelphia

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 Philadelphia

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