Drainage

[Yasai]

Given the number of things I've potted up over the past couple of years , it's a bit late to ask but could somebody please tell me... am I supposed to just cover the holes of the pot or am I supposed to put an entire layer or broken terracotta/ polystyrene?? Thanks..

[jackarmy]

Im the same, i normally cover the holes with stone or whatever, but with a growbag you just make a few slits, so it has me wondering also

[WendyC]

There is some debate as to whether crocks on the bottom improve drainage. I tend to put crocks over the large central hole in a terracotta pot, mainly to stop the compost dropping through. With a plastic pot I don't bother as there are multiple smaller holes. Also I only use plastic pots for potting on rather then permanent planting so crocking doesn't seem necessary.

[Penellype]

Same here - I will only use crocks if there is a danger of compost falling out of a large drainage hole.

[jackarmy]

Thanks both thats pretty helpfull, i use plastic pots between 10 and 25 litres with plenty of drainage holes so ill try it without for a change, saves a few quid on bags of stones

[rana]

I do not recall ever seeing a commercially grown potted plant where crocks have been used. As with others I use crocks in larger pots to prevent the compost falling through.

[chefgage]

I seem to remember seeing a study done on this. The way moisture moves from one medium to another eg from the soil to the broken pots/stones/crockery.etc and then to the ground/air obviously affects the drainage. It was found that although the general idea to put something in the bottom to help with drainage is not actually correct. Just having adequate holes in the bottom of the pot gives the same drainage properties as having something broken in the bottom. In some cases the drainage is actually better just having the soil in there.

If you think about it the idea is to get excess water away from the plants. By having the three mediums/layers eg soil to broken stuff to bottom of pot and then to air the water has got more to do in moving. By having just the two eg from soil to bottom of pot and then air the water has less effert to drain out.

[Yasai]

Thanks very much for the replies everyone; I shall take the path of least exertion then and scrap the terracotta. Cheers.

[Snadger]

In days gone by, when there was only clay pots with a single hole in the bottom there was always a number of pots that got broken by accident.
The Victorians, being an innovative bunch decided to use the broken crocks to cover the holes and stop the John Innes Soil based compost from running out the bottom of the clay pots.
Plastic pots and peat/coir/composted bark based compost put paid to that.