The USDA Zone info is a great tool for gardeners to help us determine your gardening schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The best time to plant rhubarb in Zone 4b can be estimated by using the USDA zone info.

Planting Calendar for Rhubarb

Frost tolerance for rhubarb:	Tolerant of some frost.
When to plant:	Up to 5 weeks before last frost.

Rhubarb tend to make it in a little bit of cold which means that you can plant them a bit earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant rhubarb in Zone 4b 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 rhubarb and expect a good harvest is probably August. Any later than that and your rhubarb may not have a chance to fully mature. If you are starting your rhubarb indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

On average the last frost is on May 15 in Zone 4b. In the coldest months of winter you can expect an average low temperature of -25°F.

Since the USDA zone info for Zone 4b is just an average the actual date of last frost will vary from year to year. Since half of the time in Zone 4b it frosts late in the year after May 15 be ready to protect your rhubarb in the event of a 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 your other planting guides for Zone 4b.