Before planting it is a good idea to find your USDA Zone info to determine your garden schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

The USDA zone info for Oregon can be used to determine when it's a good idea to plant trifolium.

Planting Calendar for Trifolium

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

Since trifolium are barely cold tolerant you can plant them a bit earlier in the year than more sensitive plants.

The earliest that you can plant trifolium in Oregon 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 trifolium and expect a good harvest is probably August. You probably don't want to wait any later than that or else your trifolium may not have a chance to fully mature. You can get started a few weeks earlier by starting your trifolium indoors.

Last Frost Date

On average all chance of frost has passed is on April 15 in Oregon. In the coldest months of winter you should expect an average low temperature of -5°F.

It's important to remember that the actual date of last frost may not be accurate from year to year because it is based on the USDA zone info for Oregon and it will vary from year to year. Since half of the time in Oregon you get surprised by a frost after April 15 be ready to cover your trifolium in the event of a late frost.

USDA Zone Info for Oregon

Here is the info for USDA Zone 6b.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-5°F
Highest Expected Low	0°F

This means that on a really cold year, the coldest it will get is -5°F. On most years you should be prepared to experience lows near 0°F.

Plants to Grow in Oregon

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