Also known as Monkey Poles, these are the ideal way of displaying a specimen tree individually and thus concentrating attention upon it.
- They allow you to walk around your tree, appreciating it from all angles and perhaps attending to a little judicious tidying or pest inspection.
- A solitary tree on a column receives the maximum amount of sunlight and wind. Both of these are of positive benefit in the drive to minimise leaf size and internodal distance.
- The more UV radiation any plant receives, the smaller its leaves become. This is one reason why trees at altitude are dwarf in comparison to lowland examples of the same species.
- Growths which are regularly rocked by the wind are stronger and generally shorter.
- One final benefit is that trees can easily be rotated regularly.
- As long as the tree is suited to this environment, (e.g. Pines especially and almost all species hardy in the climate in which they are displayed) this contributes significantly to their health.
Points To Bear In Mind
Trees must be well established in their pots before placing them on a column. Never place a recently repotted tree in such an exposed situation. The added strain of increased transpiration and rocking of the regenerating root ends, when it is windy, will ensure its demise.
The background must not distract, so try to site columns in such a way that they have a fairly neutral background, such as a lawn, wall, split bamboo or waney-lap fence etc. A flower border, shrubbery or hedge in the background will not be as suitable.
All columns must be absolutely stable in the high winds. A suitable foundation is necessary for cast or brick built columns. A section of telegraph pole should be sunk in the ground for roughly one third of its length and may be secured by ramming the earth solidly around it as you backfill. Alternatively fill the bottom of the hole with concrete (approx 150mm – 6″ deep) around the foot of the pole.
Brick columns may be built one brick square. i.e. two bricks side by side on each course. To have any strength at all, the construction must be well mortared and each course staggered. For a structure with greater shear strength, to withstand strong winds or accidental knocks from a lawnmower etc, use a half inch, high tensile steel rod, plumb vertical and set into the foundation. This is built into the centre of the column.
A length of telegraph pole can make a handsome upright for a column. Modern telegraph poles are pressure treated, though older ones may be found with a preserving layer of tar on the outside. The heart of these will be pale in colour, when sawn through, so the cut ends must be stood in a bucket of wood preservative overnight. This allows it to soak well into the end grain.
Concrete columns may be made from a suitably sized concrete fence post, topped with a paving slab. Alternatively a pillar may be cast using reinforced concrete or reinforced hypertufa. The reinforcement is necessary, as concrete on its own is comparatively weak in tension. Make a mould, with the column laid flat, from ply and scrap wood. Position the reinforcing bars or mesh so that they are at least half an inch in from the cast surface. This is to ensure that moisture doesn’t seep in and cause corrosion, resulting in the concrete surface spalling or falling away. Brush the inside of the mould with a release agent or a thick washing up liquid. When pouring in the concrete mix, repeatedly tap and bang the outside of the mould to ensure that all air bubbles rise to the surface.
The mould can be stripped after 12 hours and, depending upon the finish required, it may be left as is or blasted with a strong water jet to expose the aggregate.
Stone columns can be very effective if suitably shaped and sized pieces can be located. Possible sources include demolition sites, architectural antiques yards, monumental mason’s (gravestone offcuts etc) and quarries. A builder’s merchant that supplies stone may be able to help, but the pieces are likely to be small. Explain your needs and they may be able to help. If you need to change the shape of a piece of stone consider the monumental mason or do it yourself with a steel saw (obtain instruction from the hire shop, use great care, safety goggles are mandatory).
Plastic tubing has found increasing favour with exhibitors at shows for making monkey poles, as it is very strong, relatively light in weight and can easily be covered to mask its appearance. The type of tube used is normally off-cuts of alkathene gas or water main pipe. If you can secure any of this, it can also be used for garden display. Disguising the bright coloured plastic may be achieved by first roughening the surface with sandpaper and then painting with a suitable colour of textured masonry paint. Secure it in the ground by protecting the top edge with a sturdy piece of timber and then using a sledge hammer to drive it in, to a suitable depth. If this is not practical, or you require a more permanent fixing, dig out a hole and part fill with concrete, place the tube and use a spirit level to check verticality all around before completing the footing, both inside and outside the tube.
The top of a column may be a slab of treated wood, marine ply, slate, concrete or stone. Drill three holes through the part over the column and fix with coach bolts or long screws into wood or expansion bolts into brick or concrete. A dark stone such as slate has the advantage of absorbing energy from the sun and radiating heat slowly over a long period. (The more massive the lump of slate the greater the heat-store effect.) Slate can be drilled surprisingly easily using a masonry bit in a hammer drill. Pause and withdraw the bit every half inch or so to remove the dust and prevent clogging. Plastic columns may be topped with a slab of concrete, cast so that a projection will fit inside the tube.
Some method for securing the tree should be built into the top, so that it is not blown off during unexpected stormy weather. The plinth, firmly fixed to the top of the column, may have a few discreet holes drilled through it so that wire ties can encircle the pot.
Sun and wind damage are more likely to occur to a delicate tree that is elevated in a solitary position. In such cases you can either site the column so that it is naturally sheltered (though this undoes many of the beneficial effects mentioned in the introduction) or take the precaution of removing trees to a more suitable spot when necessary. Remember too that it will be beneficial, as always, to rotate the tree periodically so that it receives direct sunlight on all sides.
Having one or more display columns gives you the option to isolate a tree. This allows you to prominently display trees at the peak of perfection. Ringing the changes, with seasonal alterations to your display, will maintain interesting vistas and add another enjoyable aspect to your bonsai hobby.