One of the best tools that you have as gardeners to help us estimate your gardening schedule is the USDA zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

You should be able to estimate when you can plant polygonums by checking out the USDA zone info for San Bernardino.

Planting Calendar for Polygonums

Frost tolerance for polygonums:	Not tolerant of frost.
When to plant:	After the last frost has passed.

It's a bad idea to plant polygonums until after the last frost because they are not cold tolerant.

The earliest that you can plant polygonums in San Bernardino 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 polygonums and expect a good harvest is probably September. Any later than that and your polygonums may not have a chance to really do well. You can get started a few weeks earlier by starting your polygonums indoors.

Last Frost Date

On average the last frost when the weather gets warmer is on February 15 in San Bernardino. In the coldest months of winter you should expect an average low temperature of 25°F.

Always keep in mind that USDA zone info for San Bernardino may not be accurate from year to year and the actual date of last frost is different every year. Half of the time in San Bernardino you get a frost after February 15 so make sure that you are prepared to cover your polygonums in the event of one of those late frosts.

USDA Zone Info for San Bernardino

Here is the info for USDA Zone 9b.

Average Date of Last Frost (spring)	February 15
Average Date of First Frost (fall)	December 15
Lowest Expected Low	25°F
Highest Expected Low	30°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 30°F.

Plants to Grow in San Bernardino

You may be interested in your other planting guides for San Bernardino.