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Sand for rock gardens

Advice on creating rock gardens basically suggests three layers:  a 6” base layer of rocks and rubble, a 3” layer of sand and a top layer of a suitable soil mix to go between the larger top  rocks. 

 If the purpose of the sand layer is just to help promote good drainage is it really necessary to use horticultural sand rather than sharp sand?  In time won’t any salts in the cheaper sand just leach away?


  • Pete.8Pete.8 Billericay, EssexPosts: 6,287
    I suppose it depends on what salts, if any, are in the sharp sand.
    Salt is the most common. 
    The salt will leach into the soil and may well kill any plant roots above or below it.
    I imagine other salts could be present too, but tbh it's not something I have much experience of.

    Horticultural sand will have been washed and is a safer choice.
    I would think that horticultural grit would be a good alternative, but probably more expensive

    As you're probably already aware, builder's sand is completely unsuitable.

    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • fbwarda2gHqts3fbwarda2gHqts3 Posts: 3
    edited 22 February
    Why is a washed builders sand unsuitable provided it is a sharp sand and not a soft ? It is a coarse sharp  sand.

  • Pete.8Pete.8 Billericay, EssexPosts: 6,287
    Builder's sand is soft sand and will hinder rather than improve drainage, and often contains additives to help it bind cement
    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • BobTheGardenerBobTheGardener Leicestershire, UKPosts: 10,070
    Washed sharp sand would be fine IMO.
    A trowel in the hand is worth a thousand lost under a bush.
  • PalustrisPalustris Posts: 3,514
    edited 22 February
    I have been using Sharp sand from Builder's Merchants (even from B&M recently) for 50 years of growing Alpines  and in all that time I have never found any with salt in it. Easy enough to tell, Taste it!

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