Repotting deciduous trees

Roots beneath the trunk are severed to encourage radial roots.

Now is the perfect time to repot deciduous tress so this was the focus of the demonstration at the August meeting.
Matt made it clear that repotting is the one chance we have to check the way roots are growing and to ensure they move outwards from the trunk in a radial manner. Root pruning is also important as it encourages the development of finer, hairy roots which are those that absorb nutrients.
This process also means tap roots are removed as well as all other roots directly under the trunk.

The tree that Luke and Greg worked on was a large trunked Ash which had outgrown its pot but still required room to move so that where branches joined the trunk could become stronger and wider. The taper of the tree had already been improved by cutting back to create a new leader, even though this left scars that were quite apparent.

The importance of working on the interior root mass was emphasised because unless this is done the compacted soil close to the trunk will prevent the tree from receiving oxygen and nutrients. Digging into the area with a root hook is the principal method for creating the holes which allow root access to water and nutrients.

Greg’s Ash

A significant amount of root mass was cut from the sides and base of the tree before Greg planted it into a wider pot to maximise the the opportunity for growth. At this point it was stressed that we should never be too eager to put trees into bonsai pots as it is more important to develop spreading roots. Wide, flatter pots are the way to do this.

The red line indicates where Terry will prune in two years to create a new leader.
Image left shows roots radiating evenly from the trunk.

It was suggested that there is no need for special soil mixes for very young trees although as trees get older it is essential to allow water to drain away so that roots remain healthy. Matt uses a mix 50% organic (fine orchid bark) and 50% inorganic (pumice).

Finally, all trees repotted were anchored into their pots with wire to ensure stability.
All trees will receive Seasol, an excellent root growth stimulant and newly repotted trees will show the effects with fresh new growth in spring.