Freeze Injury Alert

March 9, 2022

Southern yellow pines acclimate to winter weather gradually. While this provides some cold hardiness, the root system of longleaf pines never really goes dormant. When temperatures drop for extended periods, or when extreme temperature fluctuations occur, there is a risk of freeze injury to seedlings. Extreme cold, desiccating winds, and sudden temperature changes may adversely affect longleaf pine seedlings.

If you haven’t planted yet, protect your seedlings.

Without the insulating properties of the soil, lifted bareroot seedlings and containerized seedlings kept outdoors are particularly vulnerable to freeze damage.

- Seedlings should NOT be planted when the temperatures are near freezing. Wait until daily highs are above freezing and the low temperatures have moderated.

- Store unplanted seedlings in temperatures above 32°.

- When conditions improve, double check a few seedlings for freeze damage BEFORE planting.

If you recently planted, stay vigilant.

Once in the ground, planted seedlings are more protected but may still be vulnerable to freeze damage at the stem at ground level and surface roots. Other concerns are that recently planted seedlings may not be acclimated to cold temperatures or the soil may not have properly settled to provide adequate insulation.

- The impact of freezing temperatures may not fully be known until the spring. Landowners should check seedlings for new growth and keep an eye on survival.

- Don’t confuse “winter burn” with actual freeze damage to the roots. Needle browning may be due to desiccation. In frozen or dry soils, the needles can lose water faster than the roots replace it. They turn brown or reddish, or in extreme cases, even yellow to white. The good news is that seedlings can usually recover from winter-burn once soil temperatures increase, and new roots and needles are initiated.

Check for freeze injury in seedlings.

For extra peace of mind, we suggest sacrificing a few seedlings to check for freeze damage.

Gently scrape the bark from the stem and roots to expose the tissue below. Look for brown, damaged tissue; healthy tissue will be white or green. Make sure to do this all the way around, as damage could be visible only on one side. Cut the stem/root lengthwise to check the pith, too – dark brown tissue indicates damage.

More resources

January 2022 Freeze Injury Conditions Alert - Southern Forest Nursery Management Cooperative

March 2022 Freeze Injury Conditions Alert - Southern Forest Nursery Management Cooperative

Cold Weather Injury to Southern Yellow Pine Seedlings - NC Forest Service