Renovation of a Mediterranean Dwarf Palm (Chamaerops humilis) Part 1

How to turn an overgrown dwarf palm into a garden highlight.

Chamaerops humilis before renovation

CChamaerops humilis is one of the most popular palms used as an ornamental feature in Mediterranean gardens. While it has decorative (and practical) advantages for a use in classic Mediterranean garden designs, it is also highly susceptible to both, neglect and an infestation by the larvae of Paysandisia archon, the now notorious palm moth. (I have previously published posts in this French Riviera Garden blog and elsewhere, that describe how to try dealing with a paysandisia infection.)

Today I am hoping to help readers with a practical description of how to renovate an overgrown Chamaerops, as it often seems to be a daunting thing to do, once it has turned itself into a bush that’s closed off from the world. Part one – today – will deal with some general tips, possible problems and a description how to attack the beast. Part two will show the finished work and how to apply a treatment against the larvae of Paysandisia archon, the palm moth.

Mediterranean dwarf palm, classic appearance when neglected and/or infected

As a preparation you will need:

  • freshly sharpened and cleaned secateurs, to avoid infections from other plants,
  • a pair of cleaned and sharpened loppers, ideally with short handles,
  • sturdy sacs to store the fronds in,
  • if you have it at hand, an electric saber saw is a great helper,
  • some cushions to kneel on, I usually put them inside of one of the thick plastic sacs
  • safety goggles, if you do it the first time
  • a baseball / golf cap to protect your head against thorns, when kneeling
  • high-quality leather gloves that cover the wrists (!)
  • quality gardening shoes
At first I’ll always have a first look all around the palm to determine where the best place to start may be, where it already grows into other plants and where a possible infestation is the most severe. Look inside the palm by opening up the fronds in order to see the work that’s ahead of you. I usually start with one of the larger outside stems, as this will quickly open up the plant’s inside. This way it’s a little easier to decide which of the young undergrowth, that comes directly from the ground, will stay. This is important since we will cut away a lot of leaves from the main stems, and we don’t want to end up with a bare plant that doesn’t show any greenery anymore. Also, the young undergrowth around the plant is rarely affected by the palm moth and possibly does feed the plant as a whole, if part of the main plant. So it makes sense to not cut all of it right from the start. So: please don’t start with strimming around the stems of the palm’s base, because it seems straight forward.

Deciding where to start a renovation of a Mediterranean Dwarf Palm

Instead, first start top down and outside in order to avoid being stung in the eye by fronds (goggles!) or hurting your arms and hands from thorns. Cut everything out that is brownish, damaged or dead. Also cut out everything that crouds the palm’s inside. I always cut at least all of the fronds off that are at 90° or more from the main axis of the respective stem. Also, only when all leaves that grow horizontally in your direction are gone, you’ll be free to move around the stems. Most of the times you will only be able to cut one leaf by coming back to it two or three more times, as, at least in the beginning, you will not be able to reach all the way to the stem. But that’s where ultimately the correct cut has to be made to achieve an overall attractive appearance.
 
This leaf was taken out near the top, it is from last year and you can see how the larvae bit a hole into it when it was still young and folded in the center of the palm above the growth point. As it grows out it shows this not so beautiful pattern.

Frond of a dwarf palm, typical signs of a previous infestation with Paysandisia archon, the palm moth

At this stage you will see a lot of 10-20 cm long leaf stubs that have been left from previous cuts. Careful, these stubs are completely dry and extremely hard. They can hurt you in many ways, and quite dangerously so. After most of the old, damaged and dead fronds are off, now comes the time to get down on our knees and cut our way bottom up, by taking off all stubs that are left on the stem; all around the stem please, not only on the visible side, but also toward the plant’s center. For this, I take the electric saber saw and move its blade’s tip leaf base by leaf base in a slight angle (about 45° I guess) toward the main stem. I try to cut close to the stem so only some neat and tidy triangles are left, which give the stem a nice ornamental appearance in the end. Sometimes the saw just rips off the complete base of an old leaf, including some of the bast fibre, but that’s ok. If you don’t have a sabre saw use the secateurs. In this case you need a steeper angle (more towards the stem) to apply enough power to cut off the stubs. This can be a rather lengthy process, but it pays off.

Lower frond stubs left from previous prunings done in the wrong way

Don’t throw leaves on the ground but cut each frond into 3-4 pieces and put them in the bin or plastic bag right away. Throwing them on the ground is less effective and can be dangerous as you can very easily slip and fall on two palm leaves, that are on top of each other; believe me I had to learn this the hard way and my hip still likes to remind me of my fault.

Top of a Chamaerops humilis with signs of heavy palm moth infestations over several growth seasons

 At the top of the stem you can see the results of palm moth infestations over many seasons. The resin and moth-munched palm matter form these clumps of hardened brown material. They are the sure sign of an  infestation which you often can spot already from the outside without cutting the fronds of.

I know, cutting everything away doesnt look that great at first, because you can see mostly the infestation, but like with all other plants, fresh cuts lead to new healthy growth, which is what you want now to save the palm. With dwarf palms new growth after a renovation cut usually is extremely quick. In the case of this palm though its not sure if we can save the two main stems, as they have been hit real hard in the past. Also last fall season the moth has attacked again, which is why you can see the damaged young leaves on top of the growth point here.

Dwarf palm, growth point showing damaged fronds in new growth

 
Now at the end of the rain season, I will leave the stem like this to dry of a little and continue with the rest of the stems. But as soon as the rotten material has dried of, I will try to take as much of it off as possible, for beauty reasons and in order to reach any possibly left larvae of the Paysandisia moth with the nematode liquid, I will apply during the next weeks.

Chamaerops palm with a cleared center, allowing for new, healthy growth and leaf stubs pruned back to the stem

Clear out all cuttings, dried leaves and any other plant debris from the inside of your Chamaerops to let light and air back into the palm’s center and all the way to the ground, and to allow it to dry off after rainfalls. Soon insects and birds will come back and enjoy this newly available space in your garden. This coming week we’ll finish this palm’s renovation cut and see if we can treat it against its infestation.

Dwarf palm at the end of the first renovation session