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.

A common way of getting a good idea when it's the best time to plant tree onions is to consult the USDA zone info for Swarthmore.

Planting Calendar for Tree onions

Frost tolerance for tree onions:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

Since tree onions do ok in moderate cold you can plant them just a tiny bit earlier in the year than other plants that might not handle the cold.

The earliest that you can plant tree onions in Swarthmore is March. However, you really should wait until April if you don't want to take any chances.

The last month that you can plant tree onions and expect a good harvest is probably August. You probably don't want to wait any later than that or else your tree onions may not have a chance to grow to maturity. You can get started a few weeks earlier by starting your tree onions indoors.

Last Frost Date

In Swarthmore the average date of last frost happens on April 15. It might get as low as 0°F during the coldest months of winter.

Just be sure to remember that USDA zone info for Swarthmore is just an average and the actual date of last frost is different every year. Half of the time in Swarthmore it frosts late in the year after April 15 so always be ready to cover your tree onions if you have a late frost.

USDA Zone Info for Swarthmore

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 Swarthmore

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