How to care for bonsai
Gardening tips: The Helpful Gardener brings the pleasure of gardening
to your home. You will find our Bonsai
articles collected in one spot. Check back often because we are constantly
adding new tips and articles.
Dormancy: Your Plants May Need a Vacation
Here 's how to accomodate those hard working plants
While I have covered plant dormancy briefly elsewhere on this
site, we continue to get a lot of questions concerning the topic, so I
will cover some more ground here. This is not a simple topic; it is of
great concern to the scientific community, even more so now with global
warming. In fact there is to be a world wide symposium in May on just
this topic (in Holland I believe), so with that thought in mind, let’s
start with a scientific explanation.
Plant dormancy defined
Plant dormancy is a form of phenotypic plasticity that minimizes exposure
to seasonally stressful conditions. Let’s break that down. Phenotypes
are observable characteristics of an organism, either from genetic make-up
or outside influence. The scientific use of plasticity denotes two things,
both of which apply in this case. In physics, something plastic is capable
of undergoing continuous deformation without rupture or relaxation; in
biology it denotes the ability to form new tissue. So what we have is
an observable phenomenon of a plant reacting to outside stimuli to protect
itself from harm, usually either too much heat or too much cold, in a
manner that does not harm the plant.
As plants develop these traits over millennia, they become so accustomed
to this dormant period that to delete it can harm the plant, and that
is the main thrust of this article. Whether the plant goes dormant to
escape the heat (those of you in the South are familiar with Virginia
bluebells and their disappearing act in late spring) or to escape the
cold (we in the New England area derive much pleasure and not insignificant
income from the foliage change as winter dormancy begins), these periods
of rest are crucial to the survival of the plant. They become particularly
tricky when we deal with bonsai; although what I will discuss
here applies to all plants, we will be paying particular attention to
bonsai dormancy requirements.
“But my plant is an evergreen; it doesn’t drop its leaves
so it’s not going dormant.” Au contraire, mon ami, the fact
that it is an evergreen plant makes the dormant period even more crucial.
While deciduous plants get a total rest, dropping all their leaves allows
the tree to send all its sugars to the roots where they are stored (that’s
why we tap maples for sugar after leaves drop), the poor evergreens do
not get the winter entirely off. They must continue to photosynthesize
and respirate as they always do, just at a much lower level than in the
So when you force that potted juniper (the most common bonsai is the
Japanese garden juniper) to grow through the winter, it gets
tired. Sure, Japanese garden junipers are a Zone 8 plant, so they’ll
handle it for the first year, even the second. I just answered a post
from a lady who had cared for her beautiful bonsai for 9 years and couldn’t
figure out why it was slipping away this season. Even I was surprised
to find that she had never given the plant any sort of cold period; usually
they won’t take that kind of sleeplessness for more than 4 years,
so she must have done everything else perfectly. Unfortunately, that won’t
save the plant now.
Giving our plants the rest they need
So what can we do to give our plants the rest they need? If you are in
a milder part of the country, and hard freezes are a rarity, simply leaving
the plants out of doors will work (remember not all plants go dormant,
so any tropicals in the collection should still go inside unless you live
in the tropics (Florida or Hawaii, even San Diego had hail this year!)
For those with a slightly cooler clime, building a tent or some such
structure over the benches you display on will usually work, I have a
friend in New Jersey who sticks his trees under his wooden deck and finds
that works fine. For those of us up here and further north, special allowances
must be made. Many of the folks in my bonsai group un-pot their trees
in early fall and plant them back in the ground on top of a piece of slate
or the like (to prevent deep rooting). Some dig sun pits (2-3’ deep
hole with a greenhouse structure over it; this is very similar to the
Chinese method, see Peter Valder's Gardens
in China for an explanation and beautiful illustrations.
The plants are placed in the pit, the pots are mulched in and the cover
sealed down. Some have greenhouses that they partition, leaving part barely
heated for the dormant trees. An unheated porch area, the corner of the
garage away from the fumes, even an unheated room in the house can be
enough cold to provide dormancy (three months at or below 50 degrees will
treat that Japanese garden juniper nicely). You can even fool trees into
thinking they’ve had a full dormancy by leaving them out for the
first two months (watch for hard weather) and then bringing them in (I
don’t recommend doing that too many years in a row).
“So we can dump the trees in our chosen locale and forget about
them until spring?” Non, mon ami, remember that our deciduous trees
are moving sugar to the roots so the roots still need to be maintained,
and our evergreens are still plugging along, albeit at half speed, so
they both need most everything they usually do (the deciduous trees don’t
need the light for photosynthesis; I know someone who over-winters his
maple in a paper box for insulation, closed).
This means watering is still our primary duty; although the requirements
have certainly dropped, we still need to check the pots and water if they
are going dry (I mean dry, over watering at this point can be deadly if
you are in a freeze thaw cycle; the constant up and down of waterlogged
soil freezing and refreezing will break roots). Rodent damage is another
consideration. I’m no fan of rodenticide, be it traps or chemical,
but if it’s them or my trees, then by whatever means necessary.
Look for chewed bark at the base of the trunk, and if you find it take
whatever action you deem appropriate.
Dormancy is a brief respite from the rigorous needs of our trees, not
a vacation. But armed with the right knowledge and tools you are prepared
to keep your tree until you both reach old age.
Have a question about your Bonsai? Ask it at our forum.
We have the friendliest bonsai forum on the net. Give it a try!
Many of them qualify for free shipping, too. They also carry some indoor
More Bonsai Articles
you should know about Tree Dormancy
Bonsai Care: Watering Requirements
Bonsai Pots and Soil
to Choose the Right Bonsai
to Prune a Bonsai
Care: Changing the shape of your tree
Photos of Bonsai