What exactly is a pot-bound plant, then?
This term refers to plants bought from garden centres, in plastic pots: and to plants in our own gardens, which are growing in decorative pots, be they plastic, wood, terracotta, stone, etc., and which haven't been repotted for months or, sometimes, years, and are starting to look less than healthy.
First, a word about what is supposed to happen with roots:
Roots are supposed to grow from the
centre of the plant, usually positioned at the middle of the pot, to the very outside of the pot, mostly horizontally. This mimics what they would do, if planted in the soil - which is every plant's life's ambition, after all.
The exception is a tap-root, which goes straight down, and which can either force its way out of the bottom of a pot, or will be forced to grow sideways inside the pot. So a plant is "pot-bound" when the roots have reached the edge of the pot, and have been forced to go round, inside.
It's less bad if they reach the sides of the pot and go downwards, but going round and round is what is called "girdling" and it is always a bad thing. As is wearing a girdle, for that matter. Generally speaking.
Most plants which we buy from garden centres etc are pot bound to some extent: in a way, they have to be, because the alternative is a plant which is not fully rooted - you know, the sort where you tip it out of the pot and half the compost falls on your feet. Garden centres would soon lose sales if they sold plants like that, so they tend to keep them until they are moderately pot-bound, in order to avoid complaints.
You can see that the roots on the side are heading downwards, not round and round. There is a thick mass of roots at the very bottom, and you can clearly see what shape the bottom of the pot was (!) so that area all needs to be cut off: those roots are tough, dry old things and won't be much use to the plant.
So take your secateurs, or an old bread knife, and cut/saw off the bottom inch or so, taking off all those hard, light-coloured roots.
Having done that, you will probably find that it's possible to gently tease out the sides as well, if you wish.
As an aside, you will often read books/articles describing the "teasing out of the roots" as though it were an essential thing to do: in my opinion, this is not always the case.
At this point, I should explain again (anyone who has ever been my Trainee, Student, or attended one of my Tree ID or self-employed Gardener courses can sing along with the chorus), that "there is no Right or Wrong in gardening": to a great extent, you do what feels right, and if it works, you do it again. If it doesn't, you do something different next time, unless you are particularly dim/optimistic/bloody-minded.
So in my opinion, for what it's worth, fluffing out the little, white, fine, feeder roots of a mildly pot-bound plant can damage them, so I prefer not to. Instead, I prefer to ensure that the planting position is properly and thoroughly prepared, so that the plant finds it easy to send those delicate little roots out horizontally again.
And by "preparation" I mean digging a hole that is quite a bit bigger than the size of the pot: enriching it, if necessary: and ensuring that the base and sides of the hole are roughed up or loosened, ie not chipping out a small pot-sized hole and ramming the poor plant into it.
Don't laugh, I've seen it done. There was one garden, once, which I was called in to "fix", where every plant had died, and when I dug up a few, I could see why: the previous gardener didn't like digging their horrible, solid clay soil, so he just carved out a pot-shaped hole for each new plant, de-potted the plants, and pushed them into the holes. As soon as they were watered (and every time it rained), the clay holes filled up with water, the roots rotted, the plants died. And what a horrible way to die, being drowned in a tiny clay pit.
So, to summarise: in my opinion, it's often better to spend time preparing the soil, rather than faffing about trying to tease out fragile roots, which might damage them.
Now let's look at a truly pot-bound plant:
It's a smallish Spruce tree, which has been in the plastic pot for rather too long, and was starting to suffer.
The leaves were going yellow, no new ones were appearing, the worried owner asked me what to do: I asked how long since it had been re-potted, and was met with a blank look.
That long, huh?
So I heaved it out of the pot.....
Here's a close-up - left - and you can see the solid wall of roots, you can see every indentation of the pot, you can even see the decorative moulding on the side.
These roots are well past their useful life: being pressed up against the edge of the thin plastic pot, they have been alternately frozen and baked, as each year passed, so they are no longer of much use to the tree.
I asked if there was a bigger pot, to pot it up into, and was told that the idea was to keep it in the same pot.
I warned the owner that the tree might not survive this treatment, and that it would be better to re-pot it into a larger pot, or preferably to plant it out properly, in the soil, somewhere: but they were adamant that it should remain in the tiny green plastic pot.
Oh-kay, then! Box-cut, it is. What's a box-cut? Keep reading, one more picture to show you first.
So, we've seen a horribly pot-bound tree: and we've seen a garden centre plant which was not that badly pot-bound: now let's look at the dangerous pot-bound ones, where you have a totally flat, often shiny, outside edge. Here's a particularly horrible example:
...and for this sort of abomination, the only answer is drastic treatment: brace yourself, and read on.
The other "dangerous" ones, by the way, are those where you can't see any soil at all, between the masses of roots, and there are nothing but big, solid, dark brown roots.
In that sort of case, then "teasing" out the worst of them can be the way to go, with the proviso that if the roots are big solid ones, you won't be able to tease them out at all.
So, in that case, and in the case of this "round cheese" thing, your only option will be the box-cut, but it will mean losing a lot of the stabilising roots.
As a generalisation, I feel that it's more important to get the rootball safely and firmly planted, than to spend a lot of time teasing out smaller roots from the sides, which are then going to be squashed back against the sides, once it's planted. But as I say, there are no rights or wrongs to this one, and it's ok to go with your instincts.
So, how to deal with the truly horrible pot-bound plant: you will often hear people referring to the X-cut, and that means doing this: (cover your eyes, if you are sensitive):
This is where you take a sharp knife and make four or more vertical slits in the sides of the pot, then you turn it over, and slash an enormous X across the base.
The idea is to break the continuity of those hard old roots, forcing them into rapid re-growth.
It works, to a certain extent: but you are left with a "wall" of the old roots around most of the plant.
Rather like leaving the plastic pot on... and don't laugh, I've seen that done, as well, but apparently I haven't written about it yet, so I'll do that later.
Right, back to the plot: if your pot is this badly pot-bound, so bad that you are seriously considering the X-cut, you might prefer to try the box-cut.
This is where you slice off the outside layer altogether, and remove the bottom couple of inches as well. Super drastic. I don't have any photos of my own, so I've had to pinch one off the internet:
Here is a sequence of three photos.
On the left, a pot-bound shrub with thick dark brown roots girdling the pot - can you see how they are going round and round?
This is baaaaad... as mentioned above, you can try teasing them out but you are most likely to snap or damage them, because they are hard and inflexible.
So, take your breadknife, and cut cleanly down - middle pic - on all four sides of the plant. Aim to skim off the minimum amount, but to get all the hard roots off.
Right-hand pic - your poor plant is now a square, instead of a round one. It has no girdling roots to restrict it. It appears to have no roots at all, but often when you do this, you will find that there are a lot of tiny roots, waiting in the wings, waiting for their chance at stardom, or possibly just freedom.
Having done this, get it planted immediately - you will, of course, have prepared your planting hole before starting the root pruning, won't you? ("questions which require the answer 'yes' ") - otherwise that newly-exposed soil will dry out, the tiny roots will shrivel and die, and so will your plant.
Sharp-eyed readers (Mal, that's you) will notice that in the picture above, they're using a pruning saw, whereas I am saying use a breadknife. That's because putting any sort of blade into soil is a seriously bad idea: soil contains actual tiny grains of rock, sand, grit etc, and these are death to sharp blades. Ask anyone with a chainsaw - you never, ever, get your chainsaw into the soil.
So I would never use my trusty pruning saw in this way: I keep an old breadknife, for such jobs, or I would just use my secateurs to chop off the bottom altogether, then skim off the sides with them.
I don't normally bother trying to get a super-neat square shape, as they did in the photos above: I am more focused on getting off the worst of the hard roots, and getting the poor thing into the soil, as quickly as possible.
So there you have it: how to deal with pot-bound plants.
And after all that plant torturing, I think we all deserve a cup of tea, and a sit-down!
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