Peppermint Willow Tree 24 Inch Box

Question from Vicki:

Can I plant this tree in a 30 inch concrete. Container? I do not want it to grow too fast.

Answer from Pat:

Agonis flexuosa ‘After Dark’ can be grown as a container plant and 30 inches is a good size, but the green species of peppermint willow tree is too large for containers. If the plant you now have in a 24 inch box is A. f. ‘After Dark’, fall would be a good time to transplant it into your larger 30-inch container. When you transplant the tree into this new container, if the root ball has been in a square box, you will need to prune the roots at transplanting time so it fits into the new round container, unless the new container is also square. If so, all you need to do is loosen the roots before transplanting, unless you find they are very matted. In that case I would prune off the matted parts.

To prune the roots and fit into a round container, first roll the tree on it’s side and using a keyhole saw, saw off 2 to 3 inches of matted root from the bottom of the root ball. Then place the tree upright again and saw off 3 or 4 inches of root from the four corners of the root ball so it will fit into the round container and have room to grow fresh roots. Place enough soil mix into the new container to compensate for the loss of height of the root ball and after lifting the tree into its new container, fill in the sides with potting soil, using a wooden dowel to shove the soil down into the container without leaving air holes. From then on, if you are happy with the size of the new container, you could keep the tree indefinitely in this container and also prevent over-growth, by root pruning every few years in fall. Simply roll the tree on its side, slide it out of the container and saw off 3 or 4 inches from the bottom roots and two opposite sides, then replace with fresh soil as described above. The next time cut off the other two sides.