8 Essential Factors for Growing Healthy Lychee Trees

1. No Wind:


Perhaps the 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 branches 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 lychees.


2. Soil Conditions:
   
   Lychees 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.
   
   Organic 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.
   
   In 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.
   
   If you 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 minors.
   
   
3. Root Zone:
   
   Keep 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.
   
   It 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.
   
   Watch 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.
   
   When 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.
   
   There 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.
   
   
4. Full Sun:
   
   If 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.
   
   Basically, 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.
   
   
5. Mulch:
   
   Organic 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.
   
   
6. Pruning:
   
   We 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.
   
   
7. Fertilizing:
   
   Lychees 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.
   
   We 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".
   
   
8. Pests:
   
   Lychee 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.
   
   Weevils 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.
   
   Weevils 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 exposure.
   
   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 applications.
   
   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.

by Bill Mee & Krystal Folino - Lychees Online
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