Which aggregate/sand should I use to improve drainage?

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ourarka

Which aggregate/sand should I use to improve drainage?

Post by ourarka »

This are is soon going to be my arids section, and before putting the weed fabric down I want to dig something in to improve the drainage further. It isn't bad now, as it is a raised bed and has some old stuff in from previous rockeries, but what would be best to dig in?
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Vagetarian

Re: Which aggregate/sand should I use to improve drainage?

Post by Vagetarian »

I'll go with grit. Sand is OK but it actually holds a surprising amount of water as it sticks to the surface of things and sand is pretty much all surface area with tiny gaps in between. Grit should help create some little air pockets. Also, not suggesting your bed has clay in it but, sand + clay = bricks. :lol:

I think horticultural grit and sand is washed so I'm not sure but you might want to rinse aggregates from a builders merchant, which are probably a lot cheaper.
Mr List

Re: Which aggregate/sand should I use to improve drainage?

Post by Mr List »

aldi were selling bags of little bits/chips of granite cheap.

when I saw them I thought 'they would be great to use for a grit mix'
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Dave Brown
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Re: Which aggregate/sand should I use to improve drainage?

Post by Dave Brown »

I spend 3 years messing adding stuff trying to turn a clay based soil into an arid area, with disastrous results :roll: everything rotted several times over. I then gave up and dug the lot out, using a ballast, pea gravel mix, with a tiny bit of loam. This worked :wink:
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ourarka

Re: Which aggregate/sand should I use to improve drainage?

Post by ourarka »

Thanks - this area is not particularly clay-ey - lucky that only a few spots in the garden have much significant clay in them. It is pretty decent soil to be honest so sounds like a bit of grit should help do the trick.
multim

Re: Which aggregate/sand should I use to improve drainage?

Post by multim »

I've found that horticultural grit works best for me...and my arid loving plants.
multim

Re: Which aggregate/sand should I use to improve drainage?

Post by multim »

Just a quick P.S. to my last message. If you are putting a membrane around the plants, it's best to cut a circle around the base of the plants to allow for air to circulate and moisture evaporation to occur. This prevents a stagnant root ball/planting hole as the plants need to breath. Any weeds can easily be pulled out.
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Dave Brown
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Re: Which aggregate/sand should I use to improve drainage?

Post by Dave Brown »

I don't use a membrane at all as it hold in moisture which you don't want ;)
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karl66
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Re: Which aggregate/sand should I use to improve drainage?

Post by karl66 »

I also agree ballast is great to add into the mix for raised bed's although how much you need depends on what exact plants your planting!, my latest sleeper bed will have various aggregates thown in including broken up tiles, ballast, quality screening soil, compost, & lots of 10mm pea gravel. I can you old limestone chippings off the roof's i strip off but i'm not to sure whether limestone would have any adverse effects on certain plants although most of it will have been washed as its been on some roofs donkey's years?. karl.
Dim

Re: Which aggregate/sand should I use to improve drainage?

Post by Dim »

I've read that if you use a membrane, you wll have no earthworms in your soil
Last edited by Dim on Sun Apr 14, 2013 7:00 pm, edited 1 time in total.
Vagetarian

Re: Which aggregate/sand should I use to improve drainage?

Post by Vagetarian »

Limestone is calcium carbonate and it will gradually raise the pH.
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Re: Which aggregate/sand should I use to improve drainage?

Post by Yorkshire Kris »

I would just use 90% grit/rock/rubble etc with only 10% soil or loam. Adding loads of grit to normal to heavy clay soil will still be too moisture retentive for most arids like agaves.
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