When can I plant Dahlia in Zone 4b

The USDA Zone info is a great tool for gardeners to help us figure out our gardening schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for our area.

You should be able to determine when you can plant dahlia by looking at the USDA zone info for Zone 4b.


Planting Calendar for Dahlia

Frost tolerance for dahlia: Not tolerant of frost.
When you should plant them: After the last frost when the weather gets warmer.

Since dahlia require warm weather it is important to wait until after the last frost when the weather gets warmer before you can plant them.

JanFebMarAprMayJunJulAugSepOctNovDec
Legend 
A good time to plant dahlia
Possibly ok, but a risky time to plant dahlia
Probably not a good time to plant dahlia

The earliest that you can plant dahlia in Zone 4b is May. However, you really should wait until June if you don't want to take any chances.

The last month that you can plant dahlia and expect a good harvest is probably August. Any later than that and your dahlia may not have a chance to grow to maturity. Starting your dahlia indoors is a great way to get them started a little bit earlier.

Last Frost Date

The average date of last frost is May 15 in Zone 4b. In the coldest months of winter we should expect an average low temperature of -25°F.

It's important to remember that our actual date of last frost is not always accurate because it is based on the USDA zone info for Zone 4b and it is different every year. Half of the time in Zone 4b we get surprised by a frost after May 15 so make sure that you are prepared to protect your dahlia in the event of a surprise late frost.

USDA Zone Info for Zone 4b

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 Zone 4b

You may be interested in our other planting guides for Zone 4b.