The most common mistake......
Posted: May 29th, 2018, 4:27 pm
...new bonsai enthusiasts make - from my observations, seems to be planting trees into too large a pot. The hope seems to be that the tree will grow faster, stronger etc. Very frequently the opposite happens. The tree becomes progressively weaker, the roots stop growing, the leaves lose their luster and cannot photosynthesize properly and cannot form the hormones necessary for root growth. The roots become weaker still. The plant looks wilted. Water is given. Fertilizer is applied. Dying roots begin to rot. The leaves are now hanging on for dear life. They (the roots) have hardly entered the new mix. The tree then either dies outright as soon as hot weather returns or languishes for months doing not much at all. How many times I've seen it I can't imagine.
Why does this happen? One reason is that we tend to apply fertilizer to match the pot size and not the tree size so there is a tendency to over-fertilize. The higher electrical conductivity (concentration of soluble salts) in the mix will inhibit root growth leading to root rot and the death spiral above. The other reason is that bonsai material is regularly top pruned. When we prune the tops we put a stop (or slow down) root growth because we remove auxins which are hormones to stimulate root extension. Auxins are produced by leaves and green stems. Particularly new ones. This does not happen with regular nursery stock which is encouraged to grow full speed without restrictions. The pot soon fills with roots and the tree remains healthy. So, we should be aware that when we prune the top, the tree will need a corresponding reduction in water and fertilizer until it builds branches and new leaves again.
Of course this is just general information and there are exceptions eg; extremely vigorous species which seem to just want to grow regardless of what we do, but even these have their limits. With slower growing plants like pines, it becomes much more important to understand the perils of large pots. The problem is made worse during winter when there is too much water entering the pots and the plant activity is slowed down and we think that just one more branch can be cut off. This is often the proverbial last straw.
All said, it is much safer to always match the pot size with the root size and give more water rather than having a large pot and hoping for the best. It often happens that a tree in a smaller pot will outgrow the same tree in a larger pot due to the above factors. You can assume to be pretty safe if you allow no more than about 50mm of room between the ends of the roots and the inside of the container for conifers and maybe twice that for deciduous trees. You will need to repot more often this way, but there is every chance your material will develop faster than you expected!
I hope that folk new to bonsai find some useful information here and avoid the most common of mistakes........
Why does this happen? One reason is that we tend to apply fertilizer to match the pot size and not the tree size so there is a tendency to over-fertilize. The higher electrical conductivity (concentration of soluble salts) in the mix will inhibit root growth leading to root rot and the death spiral above. The other reason is that bonsai material is regularly top pruned. When we prune the tops we put a stop (or slow down) root growth because we remove auxins which are hormones to stimulate root extension. Auxins are produced by leaves and green stems. Particularly new ones. This does not happen with regular nursery stock which is encouraged to grow full speed without restrictions. The pot soon fills with roots and the tree remains healthy. So, we should be aware that when we prune the top, the tree will need a corresponding reduction in water and fertilizer until it builds branches and new leaves again.
Of course this is just general information and there are exceptions eg; extremely vigorous species which seem to just want to grow regardless of what we do, but even these have their limits. With slower growing plants like pines, it becomes much more important to understand the perils of large pots. The problem is made worse during winter when there is too much water entering the pots and the plant activity is slowed down and we think that just one more branch can be cut off. This is often the proverbial last straw.
All said, it is much safer to always match the pot size with the root size and give more water rather than having a large pot and hoping for the best. It often happens that a tree in a smaller pot will outgrow the same tree in a larger pot due to the above factors. You can assume to be pretty safe if you allow no more than about 50mm of room between the ends of the roots and the inside of the container for conifers and maybe twice that for deciduous trees. You will need to repot more often this way, but there is every chance your material will develop faster than you expected!
I hope that folk new to bonsai find some useful information here and avoid the most common of mistakes........
and error which I will now avoid!