North American Fruit Explorers mailing list at ibiblio

[dwoodard@becon.org]

Yes, you do need to protect your potted apple trees. Roots in pots exposed
to winter temperatures will reach much lower temperatures than if they
were in the ground. They will also reach those lower temperaturses much
faster. Coldhardiness is developed gradually and usually peaks in January.
Soil takes a while to lose heat. A few feet down minimum temperature will
not be reached until February to May depending on depth and the minimum
temperature will be much higher than the minimum air temperature.

Roots normally do not need to be as cold-hardy as above-ground parts of a
woody perennial, and normally they are not as cold-hardy. The development
of cold-hardiness incurs a cost to the plant which could otherwise be put
into reproduction.

Back around 1981 or 1982 I bought several potted nut trees from a
nurseryman in the Niagara Peninsula (Agriculture Canada zone 7a) who had
stored them over winter in an unheated barn where they reached outside
temperatures. Many did not grow the next year.

Storage in an unheated garage that is well sealed against the entry of
cold air (masking tape will do wonders) and which has your house as one
wall might be OK. An isolated unheated building will not do you much good.

Doug Woodard
St. Catharines, Ontario


> I live in zone 6. I have several potted apple trees. Do I need to protect
> the pots from freezing in the winter? I don't have much room in my garage
> right now but would gladly leave my car outside to protect the trees if
> needed. Any advice?
> _______________________________________________