Marty

It is difficult to say what the problem is. First, though, let me say
that Iris was talking about a controlled situation in cold zone, so she
was equivalent to zone 8 or 9. I think that you are a zone that is
colder than my zone 8.

In any case, I repot all winter long with temperatures usually ranging
from about 18 at night to 60F during the day. I provide minimal
protection for my smaller plants or starters. These have the irrigation
turned on for 1 1/2 hours on frosty nights and are housed in shadecloth
covered hoophouses. Additionally, the really softer, tender plants,
mostly newly rooted cuttings are covered with reemay, a spun polyester
row cover material. The temperature under the reemay gets down to about
25F, outside the reemay but in the hoophouse probably 20F. One gallon
size plants get irrigation for an hour in the coldest part of the early
morning, but don't really need it usually. Other one gallon plants sit
right outside with no problem down to 18F. I try to give the least cold
hardy plants a bit of protection, but not much after transplanting, but
we are still talking about mid 20's at night for months before spring.

What I have discovered to be a real killer is late spring freezes. These
have been devastating for me. Our weather is very erratic in spring. We
often get a couple weeks of warm weather in March that gets everything
moving, then a hard freeze. Four years ago we had a 20F night in mid
April after everything was fully leafed out. I lost hundreds of Japanese
maples that year. But if I can avoid the freezes in spring there doesn't
appear to be a problem with winter transplanting and root pruning.
Indeed, I couldn't run the nursery if I had to do everything in Feb and
March. By the way, the hard freezes in spring are indiscriminate,
killing repotted and established plants alike if they have started sap
movement or leafed out.

Freeze drying is another possibility that you could look into. Very
cold dry air, especially if it is moving, can suck moisture right out of
the frozen stems by sublimation. Your root pruned and repotted plants
may be more susceptible to this than the established plants. That's
another reason I like to encase plants in ice when it's really cold.

One possibility is that you are getting enough sproadic warm weather in
winter to stimulate root growth after root pruning. Intact root systems
tend to stay dormant well into spring. Root pruned plants WANT to repair
and grow new roots at every opportunity. So, if you are getting
occasions where the soil temperature is getting up into the 50's or
higher for several days to a week, root growth is going to start. If
followed by a hard freeze, these roots are going to be damaged. This can
be mitigated by making sure that plants stay cool on those odd warm
winter days. Most of my plants are shaded in one way or another in
winter and the irrigated ones are encased in ice through the early
morning hours and sometimes til noon, helping to lower the soil
temperatures. I plan on painting the nursery cans white on the south
side of my unprotected pines and junipers, both to cool them in summer
AND winter to keep them from moving too early in spring. I have even had
a few pines defoliated by late winter freezes after they had started
growing. Miraculously, they can survive this. It is the only case that I
know of where a mature pine was totally defoliated and yet survived.

Bottom line is that it's a complicated process and nearly impossible to
give really good advice to someone in a place where you don't know all
the factors. But knowing the principles is the best course of action. It
may not matter if you can avoid freeze damage easily by just delaying
your repotting, but I don't have that luxury, so I must look constantly
for solutions to these kinds of problems. In any case, good luck with
your spring repotting.

Brent
EvergreenGardenworks.com


Marty Haber wrote:

Just about anything I try to transplant when the temp. is under 40F.
----- Original Message ----- From: "Brent Walston"
To:
Sent: Sunday, December 19, 2004 10:48 AM
Subject: [IBC] Repotting


Marty

What species do you have problems with?

Brent



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