One of the first steps you take when you are making a decision about your gardening schedule is find your 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.

The USDA zone info for Jefferson can be looked at to determine when it's possible 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 are barely cold tolerant which means that you can get them planted just a bit earlier than other frost tender plants.

The earliest that you can plant delphinium in Jefferson 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 delphinium and expect a good harvest is probably August. If you wait any later than that and your delphinium may not have a chance to really do well. You can get started a little bit earlier by starting your delphinium indoors.

Last Frost Date

In Jefferson the average date of last frost happens on March 15. In the coldest months of winter you should expect an average low temperature of 10°F.

Since the USDA zone info for Jefferson may not be accurate from year to year the actual date of last frost is different every year. Since half of the time in Jefferson it frosts late in the year after March 15 be ready to cover your delphinium if you have one of those late frosts.

USDA Zone Info for Jefferson

Here is the info for USDA Zone 8a.

Average Date of Last Frost (spring)	March 15
Average Date of First Frost (fall)	November 15
Lowest Expected Low	10°F
Highest Expected Low	15°F

This means that on a really cold year, the coldest it will get is 10°F. On most years you should be prepared to experience lows near 15°F.

Plants to Grow in Jefferson

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