Just what happens to plants that experience a deep freeze? Basically, the primary damage is to the cambial tissue – this is the tissue that runs from the root mass to the leaves and it’s function is to carry water and nutrients up from the roots just underneath the outer bark. Since it is mostly water filled tissue, when it freezes, it expands and ruptures. Ruptured cells are generally not regenerated and are dead.  The plant will need to regenerate from just below the line of its damaged cells and will produce a number of new terminal cells at that point.

In lay terms – a lot of the top growth will be bare, dead sticks and the plant will produce a new, very bushy, plant from either the roots or fairly low on the old plant. The good news is that if the root system escaped death, the new, regenerated plant will have a deep viable root system and a lot of energy to send upwards so the plant will put on a lot of fast growth to support the root system. The bad news is – following a deep freeze the primary damage is as I have explained – the secondary damage is deep cambial damage. The energy that the plants expend in spring to send growth up from the roots in abundance taxes a weak and damaged cambial layer. The last time we experienced freezes this deep, we saw many plants emerge in spring as if they hadn’t been phased.  They put on copius quantities of new growth in May and April and then suddenly the plant died in July and August as the growth hardened off (matured).

What happened here was that the weak cambial tissue was unable to keep up with the demands of all the new regenerated growth and it split along the trunks in mid summer – severing the life line of water and nutrients to the leaf structure.  This is called “Cambial Rupture” and you will normally see this on your woody plants (Pittosporum, Azalea’s, Viburnum’s, etc.). If this happens in summer, all you can do is cut the plant back to the ground and wait for it to grow back from the roots or replace it. If your woody plants went into the freeze well hydrated, the damage will generally be less.

Comments are closed.