Planting Site Conditions

Spring Planting

Do not begin planting until the probability of severe cold has lessened. For example, in the Northern Rockies planting generally should not begin before mid-April. Planting may begin earlier farther south. Monitor the weather forecast once planting has started. Plan to suspend planting on days when extreme cold is forecast, such as when a Canadian air mass is moving in.

Planting too early in the season can result in high mortality. Even though a site may be free of snow, do not plant when there is a chance of killing frosts or when soil temperatures are low. The moisture content of the seedlings’ stems and needles is high when they are removed from tree boxes. If seedlings are exposed to low temperatures during late freezes, the water freezes, killing the tissue.

Normally, early morning frosts do not damage seedlings right after planting, but extended cold temperatures in the lower teens and twenties cause problems. Winds can make the problems worse. Plant when seedlings are still dormant. Dormant seedlings will withstand cold better.

Do not plant seedlings during freezing temperatures and do not expose their roots to freezing temperatures during planting.

Summer Planting

Freezing temperatures can occur at high elevations during the summer planting season, especially at night. Summer seedling stock is not frost hardy. Seedlings stored on site must be protected from freezing because new root tips are easily damaged. Do not start planting when there is a chance of hard frosts.

Fall Planting

Fall-planted container seedling stock is subject to frost damage when planted later in the season (after October 1).

Seedlings planted from mid-August through September are able to harden off normally as days shorten and night temperatures fall. By mid-October, these seedlings become cold hardy and can withstand temperatures well below freezing. If severe cold (teens to low twenties) weather is forecast, delay planting until the low temperatures are expected to return to normal. The moisture content of containerized seedlings is often high when they come out of the cooler. After a few days on the site, the seedlings will lose moisture and become more resistant to freezing.