One of the first steps you take when you are figuring out 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.

It's a good idea to estimate when it's the best time to plant delphinium by referring to the USDA zone info for Onalaska.

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.

Since delphinium are one of those plants that can tolerate a tiny bit of cold weather you can plant them slightly earlier in the year than other plants that might not handle the cold.

The earliest that you can plant delphinium in Onalaska 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. You can get started a little bit earlier by starting your delphinium indoors.

Last Frost Date

The average date of last frost is May 15 in Onalaska. You should expect an average low temperature of -25°F in the coldest months of winter.

Always keep in mind that the actual date of last frost is just an average because it is based on the USDA zone info for Onalaska and it changes from year to year. Since half of the time in Onalaska it frosts late in the year after May 15 be ready to protect your delphinium in the event of a surprise late frost.

USDA Zone Info for Onalaska

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 Onalaska

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