by Krystal Folino and Bill Mee
Factors for Growing Healthy Lychee Trees
single greatest enemy of developing lychee trees is wind. When a lychee
puts out new growth these new leaves are very tender and delicate. Even
a moderate amount of wind (> 15mph) will damage these new
and leaves. Lychee trees that are well protected from the wind will
grow extraordinarily well.
When a tree flushes with new growth
it is utilizing stored energy, in the form of sugars, starches and
electrolytes, from the tree. If this new growth is destroyed or damaged
when the tree is relatively small there is little reserve left to
regenerate further replacement growth. A small tree planted in a
wind-exposed field may experience severe growth retardation by a factor
of several years.
We have successfully used bananas as wind
breaks between the trees because, in our area, they grow so fast and
are so hardy. Besides acting as attractive wind breaks, bananas produce
a lot of organic material that falls on the ground adjacent to the
prefer an acidic soil as do most tropical fruit trees. Soil pH plays an
important role in the nutritional health of a tree particularly with
respect to the trees ability to absorb minor elements such as iron.
material in the soil generates humic acids as it breaks down. These
naturally occurring acids help to lower the soil pH and promote a
healthier growing environment.
While lychees can tolerate
standing water for up to two weeks this situation is definitely not a
good one. Trees exposed to excessive water, such as those planted in a
low poorly drained area will display significant stunting of their
growth. Standing water prevents the roots from breathing and this will
eventually lead to root death and subsequently death of the entire tree.
our grove we have a certain area that gets a lot more standing water
than other sections. The trees in this area are one half the size of
other trees planted in drier sections.
Do not ever bury the root
crown of a lychee. This general rule applies to most all trees. The
root crown is the zone of plant tissue at the base of the tree between
where the roots leave off and the trunk begins. If this area is buried
by non porous soil it will lead to death of the tree just as if you
took a knife and cut a slit (girdled) the base of the tree.
are growing a lychee tree in limestone (high pH) soil such as that
found in the South Miami area it may be necessary to apply a foliar
spray of minor elements. Chelated iron is the most important of the
the root zone free of grass, weeds and any other debris that may either
steal nutrients of block them from reaching the tree's root system. As
stated before, lychees have a spreading surface root system. If you
allow grass to grow directly over and on top of the roots fertilizer
and other nutrients applied to the tree will never make it to the roots.
is typical of dooryard plantings to allow grass to grow directly
adjacent to the tree trunk. This introduces another major hazard - weed
whackers. Lawn maintenance people will attempt to use their string weed
whackers close to the tree trunk and in the process "girdle" the tree.
out for vines and tall weeds that might get started in the root zone.
There are a variety of vines whose seeds land below the leaf canopy
that when germinated can quickly envelop the entire tree in a matter of
months. These vines act to block the available sun light from reaching
the tree and will retard growth as well as making a mess.
removing vines from a lychee you should always remove the entire vine
from the tree and not simply cut the vine stem. Some arboreal vines
have so much stored energy that they will send down runners that will
reconnect with the ground and jump start the vine.
Vines, since the are usually green are hard to spot until they have
almost taken over an entire tree. Be vigilant.
is a particular obnoxious vine, similar to kudzu, that we called a
stealth vine. This sneaky vine blends in with the color of the tree and
you can look directly at one of these vines in a tree an not see it.
Before too long the vine has completely covered the entire canopy and
it is a major nuisance to remove it.
you allow a lychee to become shaded it will stop growing. If a lychee
is shaded by an adjacent tree, it will not set fruit on the shaded
section. The situation became so dire in our grove that we had to
remove every other tree.
When we first planted our grove we
attempted to maximize the utilization of space in our grove and
maximize fruit production by planting all the trees the grove would
hold. As it turned out this was not such a good idea. As the trees
developed, they grew into each other thereby "shading out" most of the
grove. Moving the trees to another grove was no small undertaking as
many of the trees were as high as 20 feet. More trees do not
necessarily mean more fruit.
If you have the land, the optimal
spacing for a lychee tree is a 15' radius from the center of the trunk
in all directions. If you leave 10 or more feet access between rows
this implies a row spacing of 40'. This may seem like a lot, but some
of the trees on the adjacent property that were planted on 30' center
30 years ago are now overshadowing each other and require major pruning.
the area around the tree should be free of other plants, trees and have
full sun exposure on all sides at some time during the east west
progression of the sun.
mulch such as that derived from yard waste and chipped material helps
to promote a uniform healthy micro-climate above the roots. This
reduces the stressful cycle of wetting and drying of the root system.
These conditions also make for a healthy environment for soil building
micro-organisms such as bacteria and fungi.
Most lychees are
propagated as air-layers (vegetative) and as such develop a shallow
root system that spreads across the surface without a deep taproot. The
decaying organic matter in mulch assists in acidifying the soil, which
is especially important in the limestone soils of the tropics and in
particular South Miami.
Lychee trees develop a hemispherical
shape that creates a canopy to naturally shade the root system.
Mulching effectively enhances the root shading properties of lychees.
have found that trees that have been pruned back about 6" after
harvesting the fruit tend to produce more fruit in subsequent years.
Pruning of the older growth stimulates new growth on all of the
meristematic terminal ends. The leads to a fuller, bushier tree that
will have a greater surface area and will probably produce more fruit.
Remember that the bloom spikes form on recent growth that has "hardened
off" within the last several months.
One objective of pruning
should be to encourage the tree to achieve the optimal hemispherical
habit of growth. This shape will provide the best shade to the root
system and encourage a healthier tree overall. Another benefit of
shading the root system out to the drip line of the tree is that the
shade deters the undergrowth of weeds, grass and undesirable volunteers
that rob essential nutrients.
exhibit a slow to moderate growth rate. This can be tremendously
accelerated through proper and effective fertilization. If your
objective is to get size on a tree rather than fruit it is possible to
push a tree very significantly during a single growing season. The rule
of thumb for fast growth is "once a month" applications of a balanced
fertilizer during spring and summer.
We have doubled the size of
some of our trees in a single growing season through aggressive
fertilization. If you are a homeowner and are in a position to lavish
TLC on your tree we would recommend using a time-release fertilizer
such as Sierra Osmacote. Time-release fertilizers release nutrients
only when the fertilizer pellets are exposed to water. Regular bulk
fertilizers may completely dissolve into the soil after a heavy rain
leading to burning of the root system and death of the tree.
have observed numerous examples of people applying a heavy fertilizer
to a tree only to watch it die after a heavy rain. If it hadn't rained
in a while sometimes it was hard to relate the cause of death to the
act of fertilizing. The giveaway to a fertilizer death is a sudden
browning of the leaves after a particularly heavy rainfall. Remember,
"a little is good but a lot is not always better."
pests are very specific to the locale of the tree. In our grove in
South Florida we get weevils, webworms and fungus. While there are lots
of noxious life forms to be found on the trees such as ants, scale,
lichens and stink bugs the big troublemakers are aforementioned nasties.
and various types of beetles seem to cause the most damage to new leave
growth, especially before the new growth has hardened off. These pests
generally will not kill a tree although the weevils can severely retard
the growth of a young tree by eating or damaging much of the new
growth, thereby slowing development. The larval form of the weevils
will eat the exterior covering of the roots and if they are in
sufficient quantity can kill the tree.
Lychee trees are more
susceptible to pathogens and fungus when they are stressed. Trees in
our grove that have been subjected to an excessive amount of water tend
to have much smaller canopies and a higher level of lichen infestation.
on the foliage are easily controlled with pesticides such as sevin. We
do not use pesticides in our grove as the marginal improvement in
productivity is not worth the long-term risks associated with pesticide
The larval weevils can be controlled by the
application of a beneficial parasitic nematode; however this is very
expensive and time consuming and is only a last resort effort when
major damage is threatening.
Many growers spray a range of
conventional pesticides, particularly to control the webworm, which
damages the small fruit after they have set. The pesticide used to
control these worms costs nearly $500 per gallon and requires several
In keeping with our organic perspective we would
rather lose some fruit rather than run the risk of the long-term
effects of low-level pesticide exposure.