Manfred writes: I am worried about the huge rubber tree in my garden. Its roots are spreading out rapidly all over the place above the soil. This is most likely because there is not enough earth underneath. It looks as if the roots have reached my house already and I am afraid that this could damage the building in the not too distant future.
On the other hand, I don’t want to remove the whole tree because it looks nice and healthy. I am therefore looking at trimming the crown and the roots rather than cutting it down. To do this I believe needs some experience. Could you please advise me about an environmentally supportive way to solve the problem?
I assume that your rubber tree is the one widely grown as an indoor plant – Ficus elastica - not the ‘true’ rubber tree – Hevea brasiliensis. Its common name derives from its milky, ‘latex-like’ sap. The leaf will identify it. F. elastica has large, oval leaves (10cm+long), dark, shiny green on the upper surface. The underside will sometimes be quite bronze, turning dull mid-green as the leaf matures.
Managing roots: Your root problem also suggests it is F. elastica. This tree is native to India and S.E. Asia. How huge is ‘huge’? Mature specimens grow to 30-40m high, with crowns of similar width. Its irregular trunk can reach 2m in diameter. It develops large, surface buttressing roots and also aerial roots to support its heavy branches.
Control will initially involve quite some effort! Have you actually dug deep enough into your soil to establish a soil profile? The topsoil is usually only 12cm – 25cm deep. Under this is the deeper sub-soil which can be much thicker. Unless you are on top of a rock shelf or some kind of obstruction lies underneath, chances are your soil profile is quite normal. The first thing to do is to cut back the roots to a point where they cannot threaten your house.
You will then need to dig a deep trench – deep enough so that there are few if any hair-like fibrous roots to be seen. You will need to place a physical barrier between root system and house. (Don’t forget garden walls – they will be pushed over before your house.) This can be something like sheet steel (expensive but probably longer lasting) or a strong concrete (at least 15cm thick – more is better).
I doubt you will find experienced tree surgeons here – indeed finding a ‘true gardener’ here is well-nigh impossible. Better to do it yourself or supervise your manual labor with an eagle eye! There are equipment hire places here and a plumber’s mechanical trencher would save the back. If concrete, I suggest you buy it in ready mixed from a reputable company, though you should calculate carefully the amount required before ordering. Don’t waste time and money by having it mixed up on the spot (usually in the middle of your driveway) as this is rubbishy stuff and will likely crumble under the ‘onslaught’ by the next wet season.
Managing the crown: No special skill is needed other than a ‘good eye’ for the shaping of the crown. Branches are solid and thick, so you will probably need a chain saw to make the task easier. Chain saws can be dangerous implements – even in skilled hands. Take care! Protective clothing and footwear should be worn. Both operator and saw should be secured by separate safety lines when working above ground. The milky sap of this tree can be very irritating to sensitive skin so wear thick gloves. A motorcycle helmet with a transparent visor gives head/eye protection.
To minimize damage to the tree, (and perhaps garden beds/onlookers) it is better to remove branches in smaller ‘nibbles’. A tree-pruning version of a chainsaw exists which is a smaller ‘blade’ at the end of 2m pole. This may be available here. The maximum thickness of branches it can handle needs to be your first enquiry. Large branches should be cut into manageable pieces and lowered by rope to the ground.
You will be fighting a constant ‘war of attrition’ against the tree which will continue to obey its ‘genetic imperatives’. Take heart in this - the first ‘attack’ will be the worst (and most expensive). A vigilant eye should keep it in check, provided it is done ‘a little and often’. Be prepared also for the possibility of the tree sending up small shoots at cut ends of the roots or in places where roots may have been broken. Attend to these as soon as detected. If caught at little more than the ‘bud stage’ they can often simply be rubbed off. If definite shoots, try to ‘tear’ them away, thereby discouraging their re-growth more than does a sharp cut.
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