If you have a tree or shrub that has been in a pot a long time, you may see that the leaves are starting to yellow and fall off. This may be due to overwatering, which can 1) wash all the nutrients out of the soil and 2) leave the roots sitting in water so they can’t breathe.
To check out the status of your potted tree, carefully tilt the pot back. If that is hard to do, it could be because the roots have gone through the base and suckered to the ground. The issue here is that those roots will have clogged the drainage hole in the centre of the base of the pot.
If possible, lie the pot on its side and gentle pull the tree out of the pot, trim the roots and repot it. However sometimes that is not very easily done as the tree becomes impossible to remove from the pot. So, what then?
Firstly, tip the pot on the side and get your drill and a masonry bit that is at least 15mm diameter and drill additional holes in the base of the pot, maybe another 4 or more depending on the size of your planter. Then drill through the original hole in the centre to clear it of the roots that have clogged it up. Overtime these holes may clog up again, but it should give the pot more opportunity to drain.
Put the pot back upright and do some cleaning up around the soil, remove suckers and trim the tree back, shape and groom to create the open vase shape.
You probably will still not be able to get the tree out of the pot, so get the drill again and a long Auger bit and drill holes (10 – 15, again depending on the size of the pot) straight down into the soil, all the way to the base. This will aerate the soil and punch through the roots and cut some of them up. These broken off pieces will die and decompose and become a food source for the microbes in the soil. This works in a similar way to taking the plant out of the pot and trimming the roots back.
Then sprinkle some food down into the newly drilled holes and water in. Finally top dress it with a good quality planting mix or compost, then cover with straw.
Done, and no broken back!
Enoy!
Peter