The best time to plant palm trees is in the Spring, after the last frosts, and planting can continue till midsummer. The dead or torn roots should be cut away and all the leaves tied up, until we are sure that the palm is well established.
Holes should be sufficiently wide and deep to accommodate the whole root system of the plants. It is ideal if these holes can be made a year in advance, and two or three sizes bigger than the root ball. Prior to planting, apply manure or humus, and allow it to decompose.
It is also important to test the drainage ability of the hole, by filling it with water.
The base of the trunk should remain at the same level as it was originally, or slightly lower in the soil. Planting palms to a somewhat higher level should only be done in very humid climates, where the drainage is difficult, as in swampy conditions.
The soil should be well pressed down around the root ball, a temporary basin made, and the palm should be given a generous watering at once.
Also, and especially if the palms are going to be planted in shady areas (they form more superficial roots), the soil surrounding the trunk should be covered with a good layer of humus or mulch, as this will help to maintain humidity, and will even regulate the temperature of the soil, while at the same time preventing many weeds from germinating.
For the humus, leaves from the palms themselves, pine bark, shavings, etc. will all be useful, although one must always bear in mind the need for a supplementary dose of nitrogen. This will help with decomposition and the transformation into organic matter that can be taken up by the plants. A good mineral fertiliser for palms contains similar quantities of Nitrogen and Potassium, as well as Magnesium, Manganese and microelements.
Water requirements. Watering:
Many palms are extremely tolerant of dry conditions, if they are already well established, but they will have a much better appearance if they receive enough water while they are in the growing stage.
We must remember that even those palms that do not reach a great height, usually spread their roots in a wide radius and to a shallow depth -the more water available, the more superficial the roots-. For this reason, watering should not be limited to just around the base of the trunk, but should go well beyond, so that a wider area is irrigated.
Again, the first and best guide in recognising the needs of a species is its origin. There are palms that appear on the border of water courses and reservoirs and there are even aquating palms (Ravenea musicalis, in Madagascar) but there also those to be seen growing in ravines and in desert regions where, normally, there is only subterranean water.
Palmitos (Chamaerops humilis), which inhabit the ravines and cliffs of the Western Mediterranean, are among those which need the least amount of water to survive.
Pruning or cleaning:
Pruning palms is a very different task from the pruning of trees or shrubs. Rather it is simply the removal of suckers we do not want and/or the fruits and dead or diseased leaves.
The bright colours, size and quantity of the fruit of some palms make a showy display. However, when species like Syagrus romanzoffiana are found in pedestrian areas, fruit falling to the ground becomes a nuisance and is best cut down.
The leaves´ longevity depend on the species and also the conditions under which it is living.
It is only justifiable to remove leaves that are still green and therefore functional and capable of carrying out photosyntesis, when they have just been transplanted -in order to reduce transpiration- or when an important part of the root system has been eliminated -trenches, etc.- or when they are subject to a long unrelieved period of drought.
On the other hand, cutting away diseased leaves helps to avoid the spreading of infection. However it is important to recognise whether the poor appearance of the leaves might be due to a mineral deficiency. In this case, their elimination could contribute to a loss of vigour in the palm.
The length of time that the dead leaves stay attached to the trunk varies. In some instances, they fall off as soon as the sheath of the leaf dries ( Archontophoenix cunninghamiana, for example). Otherwise, they can remain for several years and even indefinitely if the palms are protected from strong winds and heavy rainfall (Phoenix dactylifera, etc). Their elimination is then a personal decision or based on safety.
Unfortunately there is an almost general tendency to eliminate not only the leaves that are dead, but also those that are perfectly healthy, in the belief that this is how palm trees will grow more quickly, or with the intention of minimising the number of times the work has to be done. What is not realised is that removing a lot of green leaves will, on the contrary, adversely affect its growth and give rise to trunk constriction. So, never remove more leaves from a palm than the plant grows between each pruning.
Another very common error is to use inappropriate tools, or tools that are not well sharpened or disinfected. Cuts should always be clean, avoiding tears.
Equally, it is not a good idea to use spurs, or to cause injury to the trunk when trying to reach the crown as it will not heal over and will be open and vulnerable to the entry of pathogens.
Lastly, if we decide to cut the leaves, it is important to make sure it is done evenly all round, for it should be remembered that the sheathes and the rest of the foliage are partly what give palms their beauty and distinctive characteristics one from another.