Freeze damage of strawberry transplants

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There has been recently a spate of questions about freeze injury in strawberry transplants, so this is a topic which merits some discussion.

The freeze damage seen in transplants has been in the crown. The crown of strawberry (which is actually a shortened stem) is composed of several parts. The central part of the crown is called the pith and is made up of parenchyma cells. In plants, parenchyma cells serve to fill up the space between more specialized cells. Surrounding the pith are several more layers, in order from inside to out: the vascular layer containing the important food and water conducting elements, a cortical layer made up of yet more parenchyma cells and finally the epidermis on the very outside.

The pith is most sensitive to frost damage. The damage is caused by the formation of ice crystals in the parenchyma cells and the affected area of the pith, which is normally white, turns brown. Generally, lesser freezing injury is represented by a browning of a portion of the pith and, according to the literature, growers should expect to see little if any effect on the later growth of the plant. However, with greater injury, the pith takes on a deeper shade of brown and the surrounding vascular layer turns brown or even black. Any injury to the vascular layer will represent loss of later plant growth, since the food and water conducting elements located in this layer have been damaged or destroyed.

As a reference to the above and more detailed information, readers are encouraged to read the section on crowns found about a quarter of the way down in the following document provided by the National Agriculture Library of the USDA.

http://www.nal.usda.gov/pgdic/Strawberry/book/bok9teen.htm

The series of photos included here are intended as a rough guide to identifying and passing judgment on the severity of freeze injury in strawberry tranplants. Each caption describes the picture above it.

Healthy crown

Healthy crown. Note that pith is white and free of blemishes.

Lightly damaged crown

Freeze damaged crown. Discoloration is light and limited to pith. This plant should be OK.

Severely damaged crown

Severe freeze damage. Damage to pith is dark, and odds of damage to surrounding vascular tissue are high. This example would not be suitable for planting, because the probability of at least some yield loss is high.

Crown with low chance of survival