Clay pots have been around for a very long time. It is impossible to know for how long exactly. It is logical to say that they have been around long enough to evolve into the perfect shape for their function. Although the dimensions and proportions are variable, the basic design characteristics of the simplest and best engineered clay pots can not be improved on.
Clay pots are circular from above and below for a few reasons. Such a shape is easily formed on a potters’ wheel. It is more structurally sound than a form with flat sides and more corners. The space within is evenly distributed around the vertical center, without more remote corners. Although roots will circle within, there are not so many corners for them to congregate in.
Drainage holes are at the bottoms because that is where water drains to.
Thick rims around the top edges of common clay pots enhance durability where it is most necessary, and also prevent pots of the same size from becoming wedged into each other when stacked. The weight of stacked pots rests firmly and vertically on such rims, rather than being diverted laterally to break wedged pots to pieces.
It would not be possible to stack clay pots if they were not tapered to be wider on top. Of course, they are tapered for a few reasons, just like they are circular and outfitted with rims for a few reasons. Tapered form fits the natural dispersion of the roots of most plants better. More importantly, tapered form facilitates the removal of firm root systems with minimal disruption.
So, after perhaps thousands of years of evolution to achieve the perfect form, who thought it was a good idea to taper pots inward at the top? The lack of a rim is not so important if pots are not so numerous that efficient stacking is a concern. Such pots can not be staked anyway. They do not get reused as much as common clay pots either, so do not need to be so durable.
However, that upper inward taper is a serious problem for plants that mature and develop firm root systems within. Such mature plants can only be removed from such pots only by tearing their root systems apart, or by breaking the pots apart. Such form is only practical for big pots that contain multiple small plants that, individually, do not get big enough to fill the pots.
For example, big urns of bedding plants or mixed perennials function more as planters than as pots. Bedding plants get removed and replaced seasonally, and even if the don’t, they can not get big enough to develop a solid root system that is wider than the inwardly tapered top of a big urn. Likewise, most perennials get removed from such big pots before they get stuck within.
Palms, agaves, yuccas and other more substantial perennials must not be allowed to live within an inwardly tapered urn long enough to develop a firm root system that can not be removed.
Tony Tomeo 
Good post – I have various grasses lurking in tall, inwardly tapering pots (which I’m fond of) and, a few years on, no way of removing them to divide without breaking. I don’t think I’ll buy them again, no matter how attractive.
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If the clumps need to be divided, they can be divided into pieces for removal. I mean, you can divide them before removing them rather than after, and then remove them in pieces.
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Will try – next year, sadly! This year I’m running out of potting compost!
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Fortunately, grasses, if divided, are easier than most bulky plants to remove from such pots.
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Inwardly-tapered pots can be visually pleasing, but I didn’t know that about the roots. I just never thought about it. I just looked at my pots, and even the tall, slender one I have a tall cactus in tapers outward. Now I know why that’s important.
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It is not always important. Not only to those big inwardly tapered pots look good with a mixture of perennials and annuals that will never get stuck within, but the bulging sides prop up cascading plants, such as trailing rosemary and lobelia.
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This was so good. I do a lot of potting of perennials. Useful information that I never thought about before.
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If you use big pots, you may not need to think about it. They work fine for annuals and perennials that do not get too big for them. It is only a problem for plants that are likely to get stuck.
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I have run into plants impossible to remove!
>
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Palms that fill the top of the pot with their distended trunks are impossible! Giant yucca does that too. Breaking the pot is the only option. It is not a good option for pots that were very expensive.
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When I was a gardener I’d often get asked to re-pot these monstrosities – sometimes I could soak the mass and wash out enough soil to do an ‘extraction’ but not always.
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When I was working for a so-called ‘landscape company’ I was embarrassed that our so-called ‘gardeners’ planted things into such pots that could not be removed, and charged clients a lot of money to do it, and then charged more money to replace them. I suppose that is a profitable technique.
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I haven’t seen this ass backward pots yet. Of course, I don’t use clay pots because they would all have to be brought in for the winter. Plastic pots are kind of tacky, but the fiberglass and resin ones are better.
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They are trendy here, and can look rather stylish in the right situation. I just happen to be the guy who gets called about those that are not in the right situation.
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Reblogged this on Tony Tomeo and commented:
We installed canna for next summer into five pretty glazed pots with slim rims. I am not so keen on the pots, but they are pretty, and I do not expect canna to come out in one piece.
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They are pretty and good thoughts about what kinds of things shouldn’t be planted in them, and….you used a contraction!
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This article was recycled from three years ago, when I was trying to force myself to use contractions to improve my writing style.
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OK, I don’t understand why you don’t, but to each his own.
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Apostrophes look like mislead comas anyway.
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