Stage 2 - Goffinet noted that the initial injury is found on the outer (near the trunk) edge of the phloem bundles. (See colored regions on left)

Stage 3 -
As cold injury progresses, a greater fraction of the phloem bundles become discolored. For Goffinet's stage 3 injury, the inner phloem and the vascular cambium remains uninjured.

Stage 4 - Essentially all the soft phloem is injured. Some injury can be seen in the vascular cambium. However, the phloem ray cells are not affected.

Stage 5 - Virtually the whole phloem region including both phloem bundles and ray cells are injured. Most of the cambium is injured and a few injured cells can be seen in the outer portions of the xylem.

Stage 6 -
Total injury of the phloem and vascular cambium.

Injury is extensive to the outer xylem region and includes damage to xylem ray cells.

The shoots to the left demonstrate a range of growth that may be seen in a vineyard where trunk injury has been extensive. Shoots on some trunks do not grow at all (number 1), others grow slowly (2-4), and some grow normally (6 and possibly 5).

The reduced shoot growth most likely reflects a reduction in the amount of carbohydrate reserves available to fuel initial shoot growth, an interpution in the transport of plant hormones through damaged phloem, and water stress resulting from xylem damage.

The base of this vinewas covered with soil (hilled up) during the winter. The soil was removed before bud break.

The buried parts of the trunk, and any parts covered with snow escaped cold injury. Ttissues exposed to cold air were damaged. Although some buds survived above the snow line, shoot growth has been affected.

When shoots arising near ground level, "suckers", growt much more vigorously than than arising higher on the vine, trunk injury should be suspected.

Following a winter resulting in trunk injury, vines may suddenly collapse and die in mid-summer.

This is another sign of trunk injury.

It happens because the cold injured trunks cannot transport sufficient water to meet the increasing demand of the developing leaf canopy. Leaf stomata close, transpiration slows, leaf temperature increases.

Cold injured trunks result in heat injured leaves.

Trunks with vertical splits or cracks are found in cold vineyard regions. The common assumption is that this happens when warm temperatures cause the roots become active and "bleed" or exude liquid from pruning cuts. Active roots hydrate the trunks. Subsequent cold tempertures creates ice whose expansion bursts trunks open.

Although this scenario may happen, it is clear that most tunk splitting results from injury happening in a previous winter. Cold damaged trunks may partially recover function, but do not grow nor mature well in the following season. During the subsequent winter injured tissues do not become fully cold hardy. They are killed by almost any cold event. The vertical splits result when the dead trunks dry and shrink.

Similar splits can be seen in trunks which have been severed and allowed to dry in the sun.

Crown gall and aerial roots are another indication of cold injury to trunks.

Crown gall bacteria

The roots form when the normal basal flow of plant hormones to the root system is interupted because of cold killed tissues.