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

The USDA zone info for Zone 4b can be reviewed to estimate when you can plant gladiolus.

Planting Calendar for Gladiolus

Frost tolerance for gladiolus:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

Gladiolus tend to make it in very little cold which tells us that you can plant them slightly earlier in the year than more sensitive plants.

The earliest that you can plant gladiolus in Zone 4b 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 gladiolus and expect a good harvest is probably August. You probably don't want to wait any later than that or else your gladiolus may not have a chance to grow to maturity. You can get started a couple of weeks earlier by starting your gladiolus indoors.

Last Frost Date

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

Keep in mind that USDA zone info for Zone 4b may not be accurate from year to year and the actual date of last frost will vary from year to year. Half of the time in Zone 4b last frost occurs after May 15 so be sure to be ready to protect your gladiolus 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.