OVER - WINTERING BONSAI I
lost but a single Gingko during last years wicked weather of
alternating freezes and thaws and probably equally important it was due
to the prolonged wet period throughout. I nevertheless stress the
importance of winter protection. Mind you, this does not involve
mollycoddling one’s trees, in fact I insist that most of these plants
need a few weeks of frost, just to shut them down and perhaps kill off
a few bugs.
said, not all bonsai will survive the harsh winters that the Pacific
Northwest can have, moreover the pots may crack under the expansion of
waterlogged and frozen soil. Both are expensive cost lessons to
that are young without much bark tissue will not survive the USDA
climate zone minimums that an adult tree in the garden would. Garden
trees normally self mulch themselves as well, bonsai do not. Even in
Clallam County we have many different climate zones, depending on the
proximity of water, elevation and the factor of wind. You have to be
aware of these differences and use common sense when building a cold
frame for sheltering your small and shallow planted containers through
the winter period.
my own one-acre habitat near downtown Sequim I view at least 10 degree
F. differences depending upon the site placement of my plants. Windy
zones, frost catchment basins or poor light zones. Most conifers need
better light than I could provide under my shed.
I have always placed my evergreen plants under a cold frame that had a
removable white plastic, not clear plastic covering over it. My
deciduous plants would be under an overhang under my barn. These would
be well mulched with bark, lavender cuttings or fir bark or whatever is
sterile and weed free.
frames are usually constructed on the north side of a building. This
may work for deciduous plants, but Pines and Junipers need winter
light. I have therefore built mine on the east side of my barn and have
it oriented North to South. Orienting them otherwise will cause them
the heat up to much. Wind protection is equally important and most of
our wind comes from the west, so my barn blocks that. This N/S
orientation also gives me the option of leaving the two ends open for
air circulation. Doing otherwise would allow strong winds from the west
and east to rip the covering off.
were move able structures as I have multiple uses for them. This year I
need to replace the wood and I need to decide on 2 x6 treated wood
(unmovable) or lighter plasticized decking product.. Material needed:
One inch PVC (ideally spray painted black)and joining, wood, bolts and
screws. These have only lasted for only fifteen years.
Storing the plants outside raises the risk of damage from mice or other
small animals, so plan accordingly. Chicken wire, mouse bait and other
controls might be considered.
leaves could also be used to add extra insulation. For those plants
left out in the cold added problems exist, namely over-wet or
waterlogged conditions, that can lead to root or basil stem rot. Leaves
can create a problem however in holding in too much rainfall, so I have
started collecting lavender stems. In five years of over-wintering
plants this, pine needles or bark have proved to be the best mulching
material for me.
pots such as the forest below; create a further problem due to surface
tension. These should always be tilted with a foot under one end to
provide extra surface runoff. Mulched at an angle. This can be reversed as the months progress.
general, potted trees in the garden should be buried up to the soil
level in the pots and further mulched with straw, or bark especially
around the trunk space. Wooden pens or concrete blocks might be used to
allow for an enclosure, over which white polyethylene can be draped
over during severe weather. As this could collapse under a snow load,
it should be removed any time a snow event might occur. Rigid
fiberglass would be better.
it made of concrete as is Bill's, or of wood, they can be easily
modified for seasonal needs. In winter a simple 4x4 could be laid in
the middle with some 2x2's on either side. The mulched plants nestled
within could be quickly covered with a tarp and anchored through the
grommets to some weights beneath. I personally like those bricks that
have three holes in them. Simple to do! Cover during exceptional
freezes or heavy rains, then remove.
mulching may mitigate the cold issue, but my experience has been that
drainage and excess moisture in pots may remain the biggest problem. By
spring’s retrieval the root system becomes a rotten mush that is
usually fatal. Many cold frames also create a secondary problem and
that is ventilation. A sealed in cold frame under plastic with a snow
load can render plants susceptible to a number of fungal diseases,
resulting in a weak plant. Moreover some trees such as Pines require
those chilling periods and if kept in a too warm greenhouse will only
produce weak and spindly growths that are a waste of plant energy.
Proper ventilation and a regulated greenhouse temperature is a must.
These concrete holding frames would be great for mature Pine or
Juniper, less so for young maple trees, elms or even the so called
"hardy" Gingko. I would point out that concrete or wooden bins should
not be lined with plastic, but with a ground cloth that drains. This is
Some simple guidelines for protection and daily care in the winter
living in a place where the winter brings freezing conditions or even
snow, one has to take some precautions to bring the trees safe through
the winters. Dry powder snow is good... ice rain is not, nor is
heavy wet snow!.Always brush snow carefully off your trees as the
accumulations might worsen, freeze and accumulate more. … breaking
well aware of the species you have as bonsai. Are they in general able
to live in the climate you are living in? How cold hardy are they?
Chinese Elms, Cotoneaster, Pyracantha, Monterey Cypress, Nothofagus,
Podocarpus may need to be put into a protected cold frame or cool
greenhouse. The hardiness of Japanese and Korean Maples may vary
considerable and this link explains why.
The cold greenhouse
always place my bigger bonsais in a cold frame, or in a cold
(marginally heated) greenhouse, around the middle of November. Most of
my trees need the touch of frost to kill over wintering insects and
eggs in the bark, and to rest properly. By late March to April I
usually start bringing them out. Usually too early, and I find myself
having to bring them back in again. That error cost me dearly,
not only because of shifting weather conditions and frost, but also
because of heavy steady rains that these just wakening plants do not
usually around the end of March, but usually comes in April. It
all depends of the weather, and you will find me bringing some of my
bonsais in and out a few times, because of shifting weathers. But only
in the start and ending of the sheltering period. It can be necessary
to protect your plants from heavy steady raining periods in late autumn
as well. What may work here in dry Sequim, will not work in P.A. or Pt.
Townsend or at higher elevations that get more rainfall.
Protection from cold winds and sun
well understood are that bonsai need protections for the cold winds. It
is very important to keep any bonsai from wind exposure when their pots
and soil are frozen, because their roots are not able to take up frozen
water. Try sucking up an ice cube with a straw and you will understand.
A cold frame covered with clear plastic may also create a problem,
especially with evergreen species. Even dormant plants will continue
to transpire through the bark and buds. Dormancy does not
mean a dead stop, the plants may be slowed down very much, but the tree
continues to be active through the whole winter period.
might be a better word and more easily understood. Finely branched
deciduous trees like elms or zelkovia are damaged when cut off from
light during the winter period. When you scrape one of these fine
branches, you find a green chlorophyll layer under the thin bark. Even
though leafless, these fine branches continue to photosynthesis
during above-freezing winter temperatures. When cut off from light at
such temperatures, photosynthesis stops but but respiration through
bark and buds continues, depleting the carbohydrate reserves of the tree.
glass or clear plastic greenhouse will allow enough sun in to heat up
the trunk or leaves to a quite warm degree. If the plant is frozen,
this can lead to cracks in the bark between the two temperature zones.
The tree might also suffer from dehydration, as the leaves will attempt
transpiration although nothing is coming up from the frozen earth.
Smaller bonsai, or shallow potted trays will show the greatest stresses in this regard and should be especially protected.
Trying to recover root damaged plants.
plus' might be one mitigating commercial chemical that might help
recover some root-damaged plants. I have more suggestions that relate
more to the mature garden tree, but some of the tips may apply to
bonsai as well. The link is to my former blog "Pacific Northwest
Gardening." You may have to trudge through a 'mole article' but
the following blog relates to Climate Zones.
(C) 2009 Herb Senft.
found it amazing that no local member has ever made a comment on any of
these web postings, yet a Chinese bonsai site and a customer of mine
from Maine would make comments. (Paul P.)
"I live in a condo unit and my small area (12' x 20') is protected on all 4 sides, house and cedar fence on 3 sides.
Plants are placed among the in ground planting, against the house, under benches, and all are covered with pine needles.
temp. has gone as low as -15 degrees F.and I only lost 1 forest of 7
trees that was in a shallow pot. My pots are now deeper."
thing I do with my J. maples is put them in a lager pot filled with
pine needles and cover the whole thing with more pine needles. Also
there is a large pine in the yard that stops frost from settling on the
too have used needles as a mulch, in my own case Cedrus deodora. They
do not blow away as do leaves and are easy to apply. Since I also
manage a few income chagrined lavender farmers, I can harvest their
stems and use them as mulch and as packing material. The double
packaging that Paul P. used is great and something I had not thought to