There are several good reasons to grow palm trees in pots rather than planting them directly in the ground. Potted palms can make an exotic addition to a patio garden. They’re also great for small gardens (or no garden at all). And they’re the only choice for indoor palms.
Palm trees may be grown in a range of different pots – plastic, terracotta, metal – but do ensure that there are sufficient drainage holes and that excess water can drain away rather than pool in a saucer. As a rule palm trees prefer deep pots to shallow ones.
When selecting potting mix do remember that most palms prefer slightly acidic soil (a pH of around 6.5). If the mix is too heavy then try adding perlite or peat moss. To further improve the drainage you may wish to add a layer of pumice to the base of the pot. If not already present thoroughly mix in the requisite quantity of slow release fertiliser.
When re-potting a palm allow at least 10-15cm of potting mix between the base and the old root-ball. Try to disturb the root-ball as little as possible and carefully pack soil around the roots. Allow a gap of 3-5cm between the level of the soil at the top of the pot for watering. Once re-potted water immediately and repeat several times until the entire mix is sodden.
For outdoor palms re-potting is best carried out in spring when the weather is warm enough to allow roots to grow. Since some species may be setback a little by re-potting keep in a shaded area for a time to reduce evaporation and stress.
As with garden plants potted palms need periodic, deep watering. Since however pots will dry out faster this will need to be performed more frequently – particularly in warm weather. If you’ve a number of potted palms outside we’ve found that a simple way to keep them moist whilst on holiday during hot weather is to tape a rubbish bag around the base of each pot. Fill with sufficient water and the palm will grow happily while you’re away. For water-loving palms this can accelerate growth but beware of using this as a long-term solution as stagnant water can lead to the roots rotting – particular in cooler weather.
Unlike palm trees that are planted in the ground potted palms (and other plants) risk damage from the build up of salts in the soil. Such salts can arise both from city and bore water as well as from fertiliser. To avoid this, periodically drench the potting mix allowing the water to run through the mix.
Use a fertiliser with an N:P:K ratio of 3:1:3 with microelements. Organic fertilisers have less chance of burning the palm. As with planted palms we recommend the use of slow-release fertiliser. Never over-fertilise potted palms and be careful to apply fertiliser only to damp potting mix watering in well afterwards.
An advantage of pot-grown palms is that they may be moved to sheltered positions during particularly cold weather. If you don’t want the bother of moving pots then place any cold-sensitive palms in a location where they’ll have sufficient overhead protection from larger palms or other plants (not deciduous of course!). Providing exposure to the east will ensure that the palms warm quickly on cool mornings.
When growing palms indoors be sure to select a species that will be tolerant of lower humidity and potentially low light. In our experience the three common problems indoors palms face are; stretching from a lack of light, leaf damage from a lack of humidity and insect damage.
To combat stretching select a species that will tolerate low light conditions (e.g. Howea or Rhapis) or place the palm in a north-facing bright location. Periodically rotating the palm ensures that it doesn’t grow towards the nearest window. You may also like to consider moving your palm outside to a shaded spot in summer to benefit from better light and air.
Most popular indoor species can tolerate relatively low humidity but if you’re attempting to grow a particularly tropical species indoors you may wish to mist on warm, dry days and even consider locating the palm in a bathroom or laundry to benefit from the heat and humidity.
There are a number of insect pests that can damage indoor palms. Typical pests include aphids, red spider mite, scale and mealy-bugs. Our experience has been that regular inspection and occasional treatment of affected plants with an indoor plant insecticide solves most problems. A slightly more time-consuming treatment would be to wipe the palm with warm, soapy water. This may however need to be repeated if small areas of infestation remain.