Crocks

[Rocketron]

I was under the impression that broken pieces of flower pots were put into the bottom of larger pots as they retained moisture as well as stopping soil falling through the holes in the bottom of the pot.
A number of posters have told us they use other "stuff" such as bottle tops, polystyrene, etc. These do not retain moisture.
I am confused.

[Two_Sheds]

No, crocks aren't to retain moisture. They're just to improve drainage (and to use up broken pots)

[Florence Fennel]

Didn't GYO conduct an experiment last year with/without crocks and found it didn't make any difference? Personally I do use crocks in the bottom of pots, one or two of my least favourite pots/vases/unwanted gifts have found their way into the bottom of my buckets .....

[Rocketron]

No, crocks aren't to retain moisture. They're just to improve drainage (and to use up broken pots)

When we are told that pots dry out much quicker than the ground, why do you need to improve drainage ?

[HeyWayne]

Some "special" people wear them on their feet - and I'm not sure they helpwith drainage either.

[zazen999]

Don't use them, never shall. Don't see the point.

[snohare]

What the crocks do is help the flow of excess water through the pot from top to bottom in very wet conditions; if the steady drip stops, then the air gaps between particles fill up with water and the soil bacteria turn anaerobic, the roots cannot grab nutrients from the moisture/gas interface and...we can guess the rest.
Depends on the pot as to whether or not they need additional drainage nowadays. When the habit started in the days of clay pots, which breathe out moisture through the sides, it wasn't needed for normal summer conditions, quite the opposite, keeping the soil damp enough was likely to be the problem in good weather.
Plastic pots of course don't breathe out moisture, so need more holes in the bottom, and being more mouldable than clay have a different shape that aids drainage. But then they have a very different temperature gradient, so moisture is also more likely to evaporate off. (Or freeze.)

[COMPOST CORNER]

I believe tht crocks are only strictly necessary if a plant is to be kept in a pot for many years, however I use crocks (polystyrene broken up) in large pots, where compost may compact under it's own weight, and to fill up space to use less compost.

[Two_Sheds]

I use crocks ... to fill up space to use less compost.

me too!
pair of cheapskates, us. I save plastic bottle tops & corks, or polystyrene chunks, to fill the bottom third of a large pot. Saves a fair bit of compost.

[Two_Sheds]

When we are told that pots dry out much quicker than the ground, why do you need to improve drainage ?

Like Snohare says above.
It's to stop compost filling & blocking the drainage holes, as it can if it gets very wet and soggy.

[solway cropper]

I make a criss-cross mesh of small twigs in the bottom of pots then you can just tip it on the compost heap when you've finished and don't have to worry about fishing out bits of crock or pebbles.

[shoreham_steve]

I make a criss-cross mesh of small twigs in the bottom of pots then you can just tip it on the compost heap when you've finished and don't have to worry about fishing out bits of crock or pebbles

That's similiar to what I do - I shread tree prunings and use these. Fills up space in large pots and goes in the ground when planting out or on the 'heap' at the end of the season.