Fine Tuned Palm Gardening: Sunsitizing
Our most regular contributor provides more tips
for exotic gardening.
Don Tollefson, Venice, California, USA
Chamaerops No.34 Spring 1999
Over the years, you gradually learn what does and
doesn't work in palm gardening. As time passes, you realize that
by the time you're old, you could have done it right... if you were
just a little younger! The following tips are designed to keep you
younger by helping you move faster than time.
"Sunsitize": What's the most common
error made by palm gardeners? Failure to adequately "sunsitize"
(to properly acclimate palms to increased levels of sunlight). Beware
of the "double twos!." Too much sun, too quickly. It results
in sunburn. Just like the white-skinned beachgoer on that first
sunny day at the beach. Frequently, most or all of the palm's fronds
are damaged. This leaves only the new spear. This lonely spike now
has to provide all of the botanical exchanges required to sustain
its fully developed root system. The palm may survive. But it will
take a long time to regain its former status.
An all too frequent problem: Failure to properly
sunsitize a palm results in sunburn. Sunburn happens to some of
the most advanced palm gardeners' plants. Imagine the frequency
with which it occurs to beginners. Sunburn results in damage to
the fronds. This damage can be from minor to total. It results in
diminished growth. Diminished growth results in far less ability
for a palm to survive that first, outdoor winter. Why be off to
a terrible start? Particularly since a successful start is one of
the most important ingredients in successful palm gardening.
Plantable palms, pre-plantable palms and sunburn:
Sunburn occurs most frequently when a palm is brought directly from
the greenhouse and placed outdoors. This is a frequent occurrence
due to the popular preference of acquiring "plantable palms."
A plantable palm is one that is fully acclimated to the outdoors
and sunsitized. Plantable palms are the overwhelming choice of most
palm gardeners because they are capable of immediate, outdoor planting.
Typically, these palms come directly from the greenhouse. As such,
they are not yet plantable palms. They are "pre-plantable palms."
Preplantable palms are plantable palms that have not yet been sunsitized.
They are not yet capable of immediate, outdoor planting. Herein
lies the recurring problem: planting a preplantable palm without
first sunsitizing it.
From the greenhouse to the shade house. Failure
to sunsitize palms is a major cause of sunburn damage and setback.
Upon removal from a greenhouse, palms should be placed under shade
cloth. This enables the double transition. To acclimate and to sunsitize.
Unfortunately, palm gardeners are often uninformed and unaware that
their palms are direct from a greenhouse. This occurs most frequently
at palm sales and palm auctions. Palm sales and palm auctions are
a major source of palms for collectors. Thus, a major source of
preplantable, unsensitized palms. A recipe for sunburn. A good rule
of thumb is to assume that every palm is pre-plantable. Then follow
the time-proven technique of moving palms from the greenhouse into
the shade house. Don't skip the shade house. It's the most overlooked,
under-utilised step in palm gardening.
Shade house level: Inexpensive shade cloth
can be obtained in various shade levels from any home and garden
centre. The level of shade should be from 50% to 70%. A palm which
is removed from 50% shadecloth seldom sunburns. But it doesn't grow
as well or look as good as its contemporary under a higher level
of shade cloth. A palm which is removed from 70% shadecloth occasionally
will burn. But palms grow faster and look better under 70% shade
cloth. It's a trade off.
Erect a simple shade house: An important technique
for the beginner is to erect a simple shade house. A simple shade
house can be inexpensive and quickly erected. It's merely a shaded
area for sunsitizing palms. Then, after the palms are sunsitized,
they can be "inched" into full sun. One of the most common
tendencies with new palm gardeners is a reluctance to construct
anything. And one of the most common realisations after construction
is how easily it was accomplished.
Filtered light: An alternative to shade cloth
is filtered light. This works well if a canopy of overhead trees
exists. The palms can be positioned under the canopy with the same
results as shade cloth. From there they can slowly be "inched"
into the sun until they are ready for outdoor planting. Be careful
not to misjudge the canopy s level of shade. Also be certain that
the placement of palms is not in direct sunlight.
Timeframe: Palms can remain under shade cloth
for a period of a few weeks to a few years. A rule of thumb is to
allow them to remain under shade cloth for a minimum of one year.
One year allows the development of a complete, new set of fronds
under shade cloth. This new set of fronds is fully acclimated and
sunsitized to 30% to 50% of the available, direct sunlight. An outdoor
planted, shade cloth sunsitized palm, will perform far better then
one arriving directly from the greenhouse. Perhaps three to five
times better. That's why sophisticated shoppers of palms, first
visit the shade houses of rare palm growers. This is where the plantable
palms are located. The palms that don't come from under shade cloth
are at best, pre-plantable. Preplantable palms must first be sunsitized.
Never overlook this step. No matter where the palms come from, don't
sunburn them when you introduce them into more sunlight. Sunsitize
them first under shade cloth.
The individual shade house: The individual
shade house is one of the most valuable tools of the beginning palm
gardener. An advanced palm garden features canopy. At a minimum,
side to side canopy provided by existing palms. Even if the sun
blasts down from directly overhead, side to side relief provides
significant protection. However, most beginning palm gardeners have
no canopy. Therefore, it is impractical for them to plant palms
from the middle of July to the end of August. It is too hot. The
sun is too bright. For this six week period, some growers halt their
planting schedule. However, this is an excellent time in which to
plant. The secret is to provide an individual shade house over the
top of each palm. It sounds like quite a chore, but it can be quite
simple. Erect an inexpensive structure that will maintain shade
cloth over each palm. A structure that can be reused from year to
The inexpensive, individual shade house: The
key to success is quick, inexpensive construction. One of the simplest
methods is to construct an individual shade house from 3/4"
PVC irrigation pipe. A square top, approximately 30" x 30"
is constructed from pipe and elbows. Tees are positioned close to
all four corners. Legs extend from the tees, downward. These legs
are positioned over stakes or canes that have been driven into the
ground. Shade cloth is secured to the top with plastic ties. Voila!
An individual shade house. An individual shade house costs less
than £3.00. The average gardener needs approximately ten to
maintain the ongoing, palm gardening process. Quick, cheap and best
of all, they can be reused. The secret is to not glue them together.
Attach the parts, but don't glue them. They will remain intact.
Then, alter the sunny season, the legs can be disassembled and the
legs and tops can be stored flat. Brilliant? Yes indeed!
Pot planting and the individual shade house:
An increasingly popular palm gardening technique is the use of pot
planting in conjunction with individual shade houses. It's an outstanding
combination. This combination enables outdoor palm gardening advancements
in species and in start up success.
Anti-transpirant: Primarily, antitranspirant
is used to prevent a transplanted palm from going into shock. It
is applied to the leaves of the palm's fronds prior to the palm's
removal from soil. Generally, when a palm is removed from soil,
the result is desiccation of the leaves. Desiccation is caused by
the inability of the roots to replace the water that is transpiring
from the leaves. Desiccation results in a droopy, wilted appearance.
Obviously, the fronds can be destroyed or severely
damaged. This damage appears similar to that caused by sunburn.
Antitranspirant inhibits the release of moisture through the leaves.
This simple process prevents desiccation. It generally works to
the satisfaction of the many growers who routinely use it during
Antitranspirant, sunscreen and sunsitizing:
The past few growing seasons, palm enthusiasts have discovered that
antitranspirants prevent sunburn. Most agree that they are remarkable
for this purpose. Perhaps working better to prevent sunburn then
desiccation. Anti-transpirants perform in a similar manner to palms
as does sunscreen to humans. Thus, the interchange hereinafter of
the word "sunscreen," for anti-transpirant. Sunscreen
is first applied to the palm's fronds via a foliar spray. Then a
palm can be placed in direct sunlight with a "diminished likelihood"
of sunburn. Note the caveat, "diminished likelihood".
Growers share divergent experiences. Most have reported that the
palms performed as though they had been under shade cloth for a
year or more! Quite a remarkable discovery if it proves to be true.
Immediate uses for sunscreen: There are four
immediate uses for sunscreen. First, you can move a palm into the
sun without first sunsitizing it under shade cloth. Second, you
can protect young palms that are growing in the ground from full
sun. Young palms (those that can still be reached from the ground)
tolerate full sun. But, although they tolerate full sun, most grow
much better under filtered light. Therefore, a good policy is to
apply sunscreen to the leaves during the hot summer period. This
is a fabulous technique for the young garden that lacks canopy.
The third use is to apply sunscreen on palms that are coming into
sun from under shade cloth. This should make this transition almost
undetectable. Fourth, there is evidence that sunscreen will protect
palms from hot summer and cold winter wind damage. Sunscreen could
be helpful to prevent palm frond damage caused from cold, windy,
Effective time range: Sunscreen gradually wears
off. How gradually remains the subject of debate. Manufacturers
of most brands claim that their sunscreen will remain effective
for an entire growing season. Certain growers have verified this
to be correct. However, some growers feel that repeat applications
are necessary. Some recommend as often as every two weeks. Manufacturers
also claim that repeated applications are not harmful. The first
application is most critical. After two or three applications, subsequent
sprayings become less important. The length of time that sunscreen
remains effective continues on a trial and error basis.
Inhibited growth? Sunscreen raises the question
of inhibited growth due to its use. A possible trade-off? Not according
the manufacturers. Manufacturers' labels assure that sunscreens,
in no way, inhibit or otherwise restrict growth. Time will tell!
Sacrificial fronds: There is one final aspect
of sunsitizing. When a palm is brought from one location to another,
its fronds are introduced to a higher level of sunlight. For instance,
from the greenhouse to the shade house. Or from the shade house
to outdoors. Under even the best of circumstances, a palm's fronds
cannot adapt to a significantly increased level of sunlight. Such
fronds can endure, and survive, with little or no damage. But this
adaptation will, day by day, cause the fronds to loose their lustre
and depth of colour. The rule: A frond that was not acclimated to
a higher level of sunlight during its youth, cannot, at some latter
time, be totally acclimated to that higher level of sunlight. Thus,
advanced growers accept the fact that the current set of a palm's
fronds are "sacrificial". Sacrificial in that they will
never perform to 100%. And that the palm will not perform to 100%
until those sacrificial fronds are replaced. Replaced by fronds
that are grown, 100% on location". And 100% acclimated to where
that particular palm is located outdoors. That's why it's so important
to provide all of the assistance possible to a newly planted palm.
19-09-21 - 11:30GMT
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