One of the best tools that you have as gardeners to help us determine your gardening schedule is the 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 earliest that you can plant delphinium in Carbondale should be determined by using the USDA zone info.

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.

You can plant delphinium a bit earlier in the year because they do ok in moderate cold.

The earliest that you can plant delphinium in Carbondale 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. You probably don't want to wait any later than that or else your delphinium may not have a chance to grow to maturity. If you are starting your delphinium indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

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

Remember that the actual date of last frost is just an average because it is based on the USDA zone info for Carbondale and it will vary from year to year. Since half of the time in Carbondale you get surprised by a frost after April 15 be ready to cover your delphinium if you have a late frost.

USDA Zone Info for Carbondale

Here is the info for USDA Zone 5b.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-15°F
Highest Expected Low	-10°F

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

Plants to Grow in Carbondale

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