We are frequently asked if our trees can be planted into decorative containers and kept happily on patios or driveways for many subsequent years. Anything is possible but this is solely dependent on the amount of soil volume the tree can access. The greater the soil volume, the longer the tree can be successfully grown within its confines.
Generally speaking, for a medium or large growing tree, a root system is going to access 30 cubic metres of soil availability to support its mature form. If it runs out of space for the roots to grow into the tree will gently subsist rather than grow actively. In smaller soil volumes the roots will colonize all available space to eventually become a block of wood with nowhere else to go and in this case it is very tricky to keep the tree going in terms of water and nutrients.
Regard a large tree in a container like a caged animal, too small an enclosure leads to terminal decline. You would be excused for thinking that a one metre cube container would be big enough when you see the size of it but this will only buy you up to 5 years of adequate growth before decline sets in.
Deciduous trees are easier to manage than evergreen ones as they drop their old leaves to refresh anew each spring. Evergreen trees can look tired very quickly and in severe winters the whole container volume can freeze up as it is all above ground level with no protective insulation that the ground would normally offer. It’s not the cold that gets the tree; it’s the fact that an evergreen cannot access water to sustain its winter foliage so in effect dies of drought. This process can be referred to as freeze drying.
Once the quality of the tree in a container has been lost it is very difficult to regain it. We never advise trying to grow trees in this way for the long term as results are invariably disappointing. Some varieties work better than others. Olive, Olea europaea, can last many years and sometimes even decades in the same container if the crown is routinely pruned in the spring and the watering / fertilizer regime is adequate. On the other end of the scale, flowering cherry or fruiting trees in general would not have the root space needed to develop a crop each year and have the shortest of shelf life before declining when kept in a container.
So my advice is to max out the pot size you are contemplating and not to have too great an expectation after 5 years or so! Every square centimetre of extra soil volume buys you more time…
And one other thing, your compost should be open and friable. If you filled your container with garden soil it would compact and slump over time and deprive your roots of oxygen. It’s not easy to get it right!
For more guidance on this feel free to call is on 01353 720950 or email us on [email protected]
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