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.

You should be able to estimate when it's a good idea to plant welsh onion by reviewing the USDA zone info for Waterville.

Planting Calendar for Welsh onion

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

Welsh onion do ok in a tiny bit of cold which tells us that you can plant them slightly earlier in the year than more sensitive plants.

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

Last Frost Date

On average the last frost is on April 15 in Waterville. You should expect an average low temperature of -20°F in the coldest months of winter.

Since the USDA zone info for Waterville is just an average the actual date of last frost will vary from year to year. Half of the time in Waterville you get surprised by a frost after April 15 so just be sure to be ready to cover your welsh onion in the event of one of those late frosts.

USDA Zone Info for Waterville

Here is the info for USDA Zone 5a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-20°F
Highest Expected Low	-15°F

This means that on a really cold year, the coldest it will get is -20°F. On most years you should be prepared to experience lows near -15°F.

Plants to Grow in Waterville

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