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05/03/2014 at 09:07

There's a lot of confusion about why you add crocks to the bottom of a container. Some say to increase drainage etc.. However according to the RHS page on blackcurrants  they say add crocks to the bottom to retain moisture. I'd have quoted but this antiquated [work's] computer won't let me.

http://www.rhs.org.uk/Gardening/Grow-Your-Own/Fruit-A-to-Z/Blackcurrants

05/03/2014 at 09:19

Commonsense tells me it's for drainage. Crocks don't hold moisture.

There's always the possibility that it's one of those things that's always been done, passed on through the generations and has no purpose at all.

I've never put crocks in a pot yet

05/03/2014 at 09:35

I normally put a large stone over pot holes then grit then compost. That helps drainage and stops slugs getting in via the hole at the bottom and is a favoured place for them to lay eggs.

Polystyrene repels water and I have only used it to bulk up tall and large containers. Terracotta and cement is porous, so also no good at retaining moisture. So not sure what the RHS means by the use of such materials. If they said Biochar or hydroponic clay pebbles then yes.

Why would you put Blackcurrants in a pot? They are well behaved in the ground.

05/03/2014 at 09:59

I seem to remember that a trial was done a few years ago, by some "famous" TV gardener, which showed that there was no difference between the 2.

I fill the bottom of pots, if I want to reduce the amount of compost I use or, to increase the weight of pots that I think might blow over.

Like Nut, I suspect that it has always been done and therefore must be the right thing to do.

05/03/2014 at 10:02

I only use one or two pieces of curved broken terracotta pot, placed over the drainage hole/s in the pot, like a little bridge, to keep the hole clear of compost so that it drains freely - that's how my granny's gardener showed me how to do it.  That way the pot drains free from surplus water, but loam-based compost doesn't get washed out of the holes. 

It's not really needed with more fibrous compost. 

05/03/2014 at 10:13

I use the metal mesh sold for car repair to cover the hole at the bottom of pots. Since most of my clay pots are plunged in sand, crocks would stop the moisture from the sand going into the compost.

I think it is one of those hangovers from times past.

05/03/2014 at 10:18

I said there was confusion. I remember from my soil science days at college how confusing it was. I'm not sure I took away right knowledge. I was there for the lectures but I may have 'turned my teacher into a demon' on many occasions. (That's an Eastern philosophy quote meaning to get the wrong understanding of what is given. Just in case you were thinking I went to Hogworts. )

KEF
05/03/2014 at 11:50
Dovefromabove wrote (see)

I only use one or two pieces of curved broken terracotta pot, placed over the drainage hole/s in the pot, like a little bridge, to keep the hole clear of compost so that it drains freely - that's how my granny's gardener showed me how to do it.  That way the pot drains free from surplus water, but loam-based compost doesn't get washed out of the holes. 

That's what I do & for same reason.

 

05/03/2014 at 11:51

 

Basically, my understanding was a mixture of large particles will improve water flow, a collection of small, same size particles will impede water flow. So a fine sand won't help drainage, according to what we were told. Any barrier to water flow, such as large stones will impede water flower but in a container, the base is a large barrier.

With containers it's worth remembering that even a leaf can block the hole/holes making your container a boggy pond no matter what you put in on top. I wish that could sum it up but it really doesn't. I just wanted to share the RHS link there.  The blackcurrant bit isn't really important but there are many people that would want to grow a blackcurrant in a pot if they don't have a garden to put on in.

05/03/2014 at 11:56
KEF wrote (see)
Dovefromabove wrote (see)

I only use one or two pieces of curved broken terracotta pot, placed over the drainage hole/s in the pot, like a little bridge, to keep the hole clear of compost so that it drains freely - that's how my granny's gardener showed me how to do it.  That way the pot drains free from surplus water, but loam-based compost doesn't get washed out of the holes. 

That's what I do & for same reason.

 

 Me too, pretty much. I have used wire net to stop soil falling out and those scourers do the same job. I've also use polystyrene blocks to bulk up heavy window boxes so they're lighter. Otherwise I've use pure compost in thousands of sealed containers for even Yuccas if you can control watering. It works perfectly even in pure compost.

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