One of the first steps you take when you are estimating your gardening schedule is find your USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The USDA zone info for Rochester should be used to estimate when it's the best time to plant delphinium.

Planting Calendar for Delphinium

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

Delphinium do ok in moderate cold which tells us that you can get them planted just a bit earlier than other plants that might not handle the cold.

The earliest that you can plant delphinium in Rochester 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 delphinium and expect a good harvest is probably August. Any later than that and your delphinium may not have a chance to grow to maturity. Starting your delphinium indoors is a great way to get them started a couple of weeks earlier.

Last Frost Date

In Rochester the average date of last frost happens on May 15. You should expect an average low temperature of -25°F in the coldest months of winter.

It's important to remember that USDA zone info for Rochester is an average and the actual date of last frost is different every year. Half of the time in Rochester last frost occurs after May 15 so make sure that you are prepared to cover your delphinium in the event of a surprise late frost.

USDA Zone Info for Rochester

Here is the info for USDA Zone 4b.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-25°F
Highest Expected Low	-20°F

This means that on a really cold year, the coldest it will get is -25°F. On most years you should be prepared to experience lows near -20°F.

Plants to Grow in Rochester

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