Humidity indoors is usually low and fluctuates considerably, due to the draughts and the use of central heating and air conditioning. These fluctuations cause dehydratation of the palms, resulting in weakeness and more liklehood of succumbing to certain pests.
With a view to achieving an appropiate microclimate, palms can be grouped together, or a humidifier could be used, to increase relative humidity. Spraying water on the leaves can be counter-productive, as the relative increased humidity is of short duration and moreover, might encourage the transmission of diseases.
Unless automatized, watering is perhaps the most difficult and repetitive task to carry out in indoor gardening: over-watering, together with lack of light are the most common errors, not only in the case of palms, but in all plants found in this situation.
The frequency of watering will depend on:
- Environmental conditions, the species, the size of the palm and its vigour. We must remember that if the plants were actively growing, they would need abundant water, but on the contrary, the conditions that prevail in interiors rarely provide this facility to develop.
- The volume of space occupied by the roots, the type of substrate and container, the porosity of the container and its shape.
Both the lack and an excess of water have similar effects, as they prevent the roots from carrying water to the plant. You can use a tensiometre or other instrument to check the level of humidity in the substrate, but using your eyes and hands are also good ways to discover the amount of water needed by each palm. With very few exceptions, the substrate for palms should be more or less humid and not water-logged.
Abundant watering is preferable to giving less more frequently, as the former allows the whole root to receive water right down to its base. At the same time, any excess of salt which might have accumulated is washed away: a reduction of 50% of water contained in the substrate, would double the concentration of these salts, with consequent danger to the roots.
When the water used is hard, it is a good idea to let it stand for at least 24 hours, so that part of the calcium precipitates to the bottom. Equally, the aeration of water containing fluoride will prevent problems of toxicity caused by this element.
Every now and then, the leaves of the palms should be hosed, sprayed or simply wiped with a damp sponge that could contain a small amount of liquid soap. In this way the leaves are rid of any dust or dirt that may have accumulated, and will help reduce the likelihood of pests such as scales and red spider.
The use of cleaners or brightners used for other indoor plants is not recommended, due to the fact that palms are monocot plants and therefore contain a similar number of stomata on the surface of the leaf and on the underside. Their application could block a great many of these microscopic pores.