by Alan W. Meerow and Timothy K. Broschat
Palms have a deserved reputation for ease of transplanting
relative to similarly sized broad-leaved trees. The common
sight of tractor trailer loads of 20 foot tall or larger palms
are testamonial to this fact. Nonetheless, transplant failure
is not unknown, and replacement percentages can rise as high
as 30% or more on an installation. Such failures can be greatly
minimized with improved understanding of how palm root systems
regenerate after digging from a field nursery, a landscape
site, or the wild, and by paying greater attention to the
care received by the palms in the first critical months after
installation. The purpose of this circular is to describe
and discuss these factors, and suggest optimum conditions
for successfully transplanting specimen size palms.
Harvesting Palms for Installation
Developmental Age and Transplant Success
Palms, unlike broad-leaved woody trees, complete stem caliper
growth before beginning substantial height increase. During
this "establishment phase" (Tomlinson 1990), the
root initiation zone at the base of the stem is developed
to its fullest potential. Consequently, palms are not very
tolerant of the extreme root disturbance that accompanies
digging from a site of previous growth until visible trunk
development has taken place (Broschat and Donselman 1990a).
This is most critical for species that characteristically
complete a great deal of stem development deeply below ground
(for example, Bismarckia noblilis, Latania spp., Sabal spp.).
Even if the palms are not killed by premature transplanting,
growth setbacks and possibly less than optimum caliper development
may occur. Young palms (that is, without visible trunk development)
should thus be transplanted only from containers.
Time of Year and Transplant Success
Palms establish most quickly if transplanted during the spring
and early summer when soils temperatures are on the increase.
Many tropical palms exhibit reduced root function at soils
temperatures below 65o F. An additional advantage is the higher
rainfall normally experienced during this time in Florida,
thereby reducing the need for supplementary irrigation during
the first critical months of establishment. In south Florida,
time of year is not as critical from the perspective of temperature,
though mid-winter planting should be avoided if possible.
Patterns of Palm Root System Regeneration and Root Ball Size
Research has determined that palms vary in their root regeneration
response when dug (Broschat and Donselman 1984a, 1984b, 1990b;
Table 1). For queen palm (Syagrus romanzoffiana), royal palm
(Roystonea regia), Mexican fan palm (Washingtonia robusta)
and Senegal date palm (Phoenix reclinata) the percentage of
cut roots that branch and continue growing is directly proportional
to the length of the remaining stub. This would argue for
including the largest root ball possible for these species
when digging, at least from the perspective of root survival
in the landscape. A one foot minimum radius (from the trunk)
is recommended for these palms. While a larger root ball may
well increase transplant success, the additional weight and
costs involved in transportation may not justify the slight
gains in post transplant survival. It should also be kept
in mind that the vertical length of the root ball is often
larger than the horizontal radius on palms dug from a field
or landscape site, thus vertically oriented root stubs will
likely be longer than these minimum recommendations.
Queen palms will likely survive with a root ball of 6 inch
radius, but a larger root ball will increase root survival
at the landscape site. Root branching in coconut palms (Cocos
nucifera) does not appear to be dependent on the size of the
root ball. In sabal palms (Sabal palmetto), virtually all
of which are dug from native stands rather than nursery grown,
negligible root branching occurs, and new roots must be initiated
from the trunk. For these two species, smaller root balls
are acceptable. For palms that must regenerate new roots from
the trunk, root-pruning 2-3 months before digging will provide
adequate time for new root growth within the ball.
From the list of palms whose root regeneration patterns have
been studied (Table 1), it appears that the most common response
is 1) some degree of branching of cut roots, the percentage
increasing with the length of the stub (up to a point) accompanied
by 2) some variable degree of new root initiation from the
trunk base (Fig. 1). In general, for single-stemmed palms
less than 15 feet in height, a root ball of shovel width radius
from the trunk is a common industry average for size and should
provide for adequate root survival in those species exhibiting
that response (Fig. 2). For clustering or larger solitary
specimens, an incrementally larger root ball may be advisable
to insure successful establishment under site conditions that
may be less than ideal. An obvious concern for the field grower
is to minimize loss of soil from the field.
Specimen-sized palms that are containerized after harvest
for the interiorscape market and smaller, containerized mass-market
palms usually have the root ball trimmed further before containerization.
Such palms are moved into shade structures for acclimatization
where growing conditions are optimal for root system regeneration.
Root pruning has generally not been considered necessary for
palms, with the exception of Bismarck palm (Bismarckia nobilis)
and a few others. However, all of the species so far examined
also produce new roots from the trunk base (Table 1), in addition
to any root branching, when dug. This would strongly suggest
that all palms would benefit from root pruning 4-8 weeks before
digging from the harvest site to encourage new root initiation.
Of course, this would add a substantial labor cost for either
the grower or installer. However, if the species is a particularly
high value palm for which replacement costs would be expensive,
the extra labor may well be cost effective.
Digging the Palm
Palms can be dug by hand, with gasoline powered tree spades,
or spades mounted on small tractors. Soils that cling to the
root ball are the most amenable to mechanized harvest. Palms
grown in very sandy soils, which may fall away from the roots,
might require hand digging. Prior to digging, the soil around
the root system should be thoroughly wetted to help keep the
root ball together. Palms grown on sandy soils will usually
to need to have their root balls burlapped after digging,
while palms grown on soils with greater structural integrity
may not require burlapping. If the dug palms will be held
in storage in the field for some time before shipment, burlapping
may also be necessary, regardless of the soil type. In such
situations, the root ball as well as the trunk and foliage
should be periodically moistened.
Preparation for Transport
When moving palms out of the field, they should be well-supported
to prevent injury to the tender heart. Some palms (for example,
King Alexander, Archontophoenix alexandrae) are much more
sensitive to heart injury due to rough handling than others,
and require extra care in transport. For certain species with
slender trunks (for example, Senegal date, Phoenix reclinata;
Paurotis palm, Acoelorrhaphe wrightii), a supporting splint
should be tied to each trunk and should extend into the foliage
to protect the bud. Palms with very heavy crowns (for example,
Canary Island date palm, Phoenix canariensis) should be braced
similarly to prevent the weight of the crown from snapping
the bud. Stems of clustering palms should also be tied together
for additional support.
A tree crane is usually required to lift large palms out of
the field, and the trunk should be protected with burlap or
other material wherever ropes, cables, chains or straps will
be attached (Fig. 3).
The greatest loss of water in newly dug palms occurs from
transpiration through the leaves. To minimize this, one half
or more of the older leaves should be removed at the time
of digging. The remaining leaves should be tied together in
a bundle around the bud with a biodegradable twine. The best
method of insuring survival after transplanting to the landscape
may be to remove ALL leaves on species like sabal palms that
must regenerate all new roots from the trunk (see below, Special
Cases). Complete leaf removal may also be advisable during
installation of any species where normal post-transplant irrigation
is impossible. However, many buyers will object to this practice
for aesthetic reasons. Where practical, misting or irrigation
of the foliage may reduce water loss during the transplant
process, though there is an accompanying risk of increasing
disease problems in the canopy.
It is always best to install newly dug specimen palms immediately
to minimize stress and possible loss of the palm. If delivered
palms cannot be planted immediately upon arrival at the installation
site, the palms should be placed out of direct sun and the
trunk, root ball and canopy kept moist. Temporarily "heeling
in" the root balls under a layer of mulch is advisable,
especially if other no means of keeping the roots from drying
out is available (Fig. 4).
Installation site conditions also contribute to the establishment
success of transplanted palms. A well drained location is
essential; standing water should not appear at the bottom
of the planting hole. If drainage is a problem at the site,
a berm should be constructed to raise the root ball above
the level of water. Though some palm species may adjust to
less than optimal drainage after establishment, standing water
around a newly dug root ball will have adverse effects on
The planting hole should be wide enough to easily accept the
root ball and provide at least several inches of new growth
from the ball. It need only be deep enough to situate the
palm at the same depth at which it previously grew. The amending
of backfill soil from the planting hole is not recommended.
If the backfill soil differs greatly in structure and texture
from the surrounding site soil, new roots will have a tendency
to remain within the backfill. If amending the backfill soil
is demanded by the customer, the volume of amendment should
not exceed 25% of the soil removed from the hole.
Planting and Support
It is imperative that palms not be transplanted any deeper
than they were originally grown (Fig. 5). The root initiation
zone at the base of the trunk is extremely sensitive in this
regard, and planting too deeply will cause root suffocation,
nutritional deficiencies, root rot disease and frequently
loss of the palm. Unfortunately, it is still a common practice
for installers to situate specimen-sized palms at various
depths in order to create a planting of uniform height. The
decline of deeply planted palms may take several years to
become apparent, especially on very well-drained soils, but
it can only be reversed by removing the backfill from the
suffocated root initiation zone or replanting the palm.
All air pockets should be tamped out of the backfill as the
planting hole is filled. A berm should be mounded up at the
periphery of the root ball to retain water during irrigation.
The initial irrigation should be deep and thorough. Filling
the planting hole with water up to the berm will be necessary
2-3 times to fully wet and settle the soil.
Larger palms will require some form of bracing to maintain
stability during the first 6-8 months after installation.
The proper method of support is illustrated in Figure 6. Short
lengths of 2" x 4" lumber should be banded or strapped
to the trunk (a foundation of burlap or asphalt paper can
be placed around the trunk under these), and support braces
(also 2" x 4", or 4" x 4" on very large
specimens) are then nailed into them. Under no circumstances
should nails be driven directly into a palm trunk. Such damage
is permanent, and provides entryway for pathogens and possibly
insect pests as well.
The root ball and surrounding backfill should remain evenly
moist, but never saturated during the first 4-6 months after
installation. Supplementary irrigation is necessary unless
adequate rainfall is received during this time period. Newly
transplanted specimen-sized palms should not be expected to
produce a great deal of new top growth during the first year
after transplanting; much of the palm's energy reserves will
(and should) be channeled into root growth. Drenching the
root zone 2-4 times during the first few months with a fungicide
labelled for landscape use on soil borne root fungal pathogens
is recommended for high value palms. A light surface application
of a partially slow-release "palm special" granular
fertilizer can be banded at the margins of the root ball 3-4
months after transplanting. A foliar spray of soluble micronutrients
may be beneficial during this period, since root absorption
activity is limited. Macronutrients (nitrogen, phosphorous,
potassium, magnesium) are negligibly absorbed through the
leaves, and should not be applied as a foliar feed. When the
appearance of new leaves indicates that establishment has
been successful, a regular fertilization program (3-4 times
per year optimally) can begin (see "Palm Nutrition Guide,"
Extension Circular SS-ORH-02).
Cabbage or Sabal Palms
Sabal palms are the most widely planted of all palms in the
southeastern United States. Virtually all are dug as mature
specimens from natural stands because their slow growth rate
makes nursery production uneconomical. Survival rates for
transplanted sabal palms are often low. In sabal palm (Sabal
palmetto) virtually no cut roots survive, regardless of length.
Thus, transplanted sabal palms have no functional root system
for the six to eight month period required for the production
of new adventitious roots from the root initiation zone at
the base of the trunk (Broschat and Donselman 1984a).
The standard procedure for transplanting field-grown sabal
palms has been to remove the lower two-thirds of the leaves
and tie the remaining leaves into a tight bundle around the
bud to reduce transpiration. The remaining leaves typically
become desiccated and die within one to two months and the
palms may appear to be dead. If the palm survives, new green
leaves will eventually emerge from within the canopy of dead
Broschat (1991) monitored an installation of several hundred
sabal palms with trunks from 10-20 feet long in a street median
landscape in Miami, Florida. Approximately half were transplanted
using the standard practice of removing all but the top one-third
of the leaves and tying these remaining leaves up with biodegradable
twine. The other half had all leaves removed prior to transplanting.
All palms received soil irrigation as needed during the eight
month evaluation period. The survival rate for palms transplanted
without leaves was 95%, compared to 64% for those transplanted
with one-third of their leaves remaining. Among the surviving
palms, canopy size was slightly smaller for palms transplanted
with leaves. In addition to the lower survival rate for palms
transplanted with leaves, the fact that all the original leaves
died and had to be later removed by hand makes this practice
costly in terms of labor requirements.
Complete leaf removal appears to be the best method for transplanting
sabal palms, which lose all their roots in the transplant
Palms Susceptible to Palmetto Weevil Infestation
Palmetto weevils (Rynchophorus cruentatus) are large beetles
that are drawn to stressed palms. They most frequently attack
cabbage palms (Sabal palmetto) and Canary Island date palms
(Phoenix canariensis), but have been reported on Mexican fan
palms (Washingtonia robusta), Bismarck palms (Bismarckia nobilis)
and latan palms (Latania spp.) Adult females lay eggs in the
leaf bases of the crown, and the large larvae quickly tunnel
into the heart, destroying the palm (Fig. 7). All efforts
should be made to reduce transplant stress on susceptible
species. A preventative spray of either Lindane or Dursban,
applied at and again several weeks after installation, has
shown some success in keeping palms free of infestation (Giblin-Davis
and Howard 1988).
Acclimatization of Interior Specimens
It is absolutely essential that palms intended for the low-light
conditions of the interiorscape be subjected to an acclimatization
period of at least one year under shade (Broschat et al. 1989)
after transplanting from full sun conditions. Leaves produced
in full sun will not survive under low-light conditions and
must be replaced by new leaves produced in shade. The amount
of time necessary for complete replacement will vary with
species, but one leaf every two months is a reasonable average
across a broad spectrum of palm species.
Broschat, T. K. 1991. Effects of leaf removal on survival
of transplanted sabal palms. J. Arboriculture 17: 32-33.
Broschat, T. K. and H. M. Donselman. 1984a. Root regeneration
in transplanted palms. Principes 28: 90-91.
Broschat, T.K. and H.M. Donselman. 1984b. Regrowth of severed
palm roots. J. Arboric. 10: 238-240.
Broschat, T. K. and H. Donselman. 1986. Factors affecting
palm transplant success. Proc. Fl. State Hort. Soc. 100: 396-397.
Broschat, T. K. and H. Donselman. 1990a. IBA, plant maturity
and regeneration of palm root systems. HortScience 25: 232.
Broschat, T. K. and H. Donselman. 1990b. Regeneration of severed
roots in Washingtonia robusta and Phoenix reclinata. Principes
Broschat, T. K., H. Donselman and D. B. McConnell. 1989. Light
acclimatization of Ptychosperma elegans. HortSci. 24: 267-268.
Giblin-Davis, R. M. and F. W. Howard. 1988. Notes on the palmetto
weevil, Rynchophorus cruentatus (Coleoptera: Curculionidae).
Proc. Fla. State Hort. Soc. 101: 101-107.
Tomlinson, P. B. 1990. The Structural Biology of Palms. Clarendon