One of the best tools that you have as gardeners to help us determine 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.

By reviewing the USDA zone info for Washington it's possible to determine when it's the best time to plant iresene.

Planting Calendar for Iresene

Frost tolerance for iresene:	Not tolerant of frost.
When to plant:	After the last frost.

It's probably a bad idea to plant iresene until after the last frost when the weather gets warmer because they are not cold tolerant.

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

Last Frost Date

The average date of last frost is April 15 in Washington. You can expect an average low temperature of -15°F in the coldest months of winter.

Keep in mind that the actual date of last frost is just an average because it is based on the USDA zone info for Washington and it can change quite a bit from year to year. Since half of the time in Washington you get surprised by a frost after April 15 be ready to cover your iresene if you have a late frost.

USDA Zone Info for Washington

Here is the info for USDA Zone 5b.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-15°F
Highest Expected Low	-10°F

This means that on a really cold year, the coldest it will get is -15°F. On most years you should be prepared to experience lows near -10°F.

Plants to Grow in Washington

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