Why is sand bad??

[emilleejoyce]

I was hunting around the forum for info on repotting and soil types, and someone mentioned that sand was a death sentence for cacti. Why is that?? From my experience, sand drains easily, so shouldn't it be fine??

I'm planning on replanting an aloe plant I just bought, and while it's not a cactus, I was basically going to treat it like a cactus in terms of soil. I don't have a lot of money to go out and buy all these things like pumice and perlite and blah blah blah so I was thinking of using sand, but now I'm worried. What makes sand so bad??

[luddhus]

I have not tried planting cacti in pure sand, but it sounds like a bad idea. Even if sand drains fast it still holds a lot of water that evaporates slowly, and a growing medium that stays wet for long usually kills the plant. I tried (a long time ago) to mix a small portion of sand with coarser material, but it made the mix unnecessarily heavy with little or no positive effects (the plants survived, however).
I mostly use products similar to the Napa floor-dri, Turface etc. that are available in the US.

[emilleejoyce]

Oh I guess I should elaborate. I don't mean potting a plant in pure sand, I'm talking about mixing it with other mediums. Like in the example cactus mix on this website, why can't sand be substituted for the pumice??

[charlpic]

All in all, the finer the sand, the worst...
It packs up your mix, doesn't help to have a good air flow and can eventually clog the pot.

[iann]

Sand clogs up the gaps in your soil that would allow water to drain and air to stay around the roots. Fine sand obviously clogs much worse but you need to go to about 1/8th" before it makes things better instead of worse, and I don't call that sand any more. Sand in an open bed drains fast but sand in a pot is just a disaster.

[Saxicola]

Perlite shouldn't be that expensive. Just don't buy it at a fancy nursery where everything is overpriced (or that Miracle Grow stuff with fertilizer already in it). I like pumice better (perlite is more prone to float when you water it) but they do tend to overcharge for that. If I was forced to choose between regular potting soil or potting soil mixed with regular playground/beach type sand I'd do pure potting soil, but that is a lesser of two evils choice.

[amanzed]

Yeah, you can actually add sand to PROLONG moisture retention in some mixes. Even though it's "gritty", the grain sizes are small enough that it actually retains much more water—for much longer—than you'd think by intuition alone. In the ground, much of this moisture is conducted away by capillary action. In containers it is retained for a long time. Some species don't care about this (lots of mesemb growers use sand in their mix), but it definitely doesn't take the place of pumice/perlite/Napa.

[tudedude]

Yup, adding pumice or perlite is as much about adding air circulation to the roots as it is about drainage. A bag of perlite at home depot probably costs the same as a bag of sand.

[Steve Johnson]

Yup, adding pumice or perlite is as much about adding air circulation to the roots as it is about drainage. A bag of perlite at home depot probably costs the same as a bag of sand.

I don't recommend Perlite because it floats away, and this makes it a pain in the backside when using it for cactus mixes. I can find pumice easily, but that's SoCal, so I don't know about what the situation might be for other folks. In the absence of pumice, perhaps Turface or NAPA Floor-Dri would be better.

[cactushobbyman]

I have an area outside where I had to make repairs to my septic tank area. After the repair the area was back filled with construction sand. I use this area for cactus and all are growing great. Nothing else but pure sand. This is outside, not pots.

[Harriet]

Get NAPA Floor-dri if you have a place to store the bag, Perlite if you need only small quantities. I think that the NAPA stuff is the better choice. I have not found a good source for pumice on the east coast, but again, if you only need a small quantity, it can be ordered on line.

[leland]

Where I lived in AZ the soil was ``sand``. Actually it was river silt, a very fine sand. Locally it was called ``blow sand``. After a rain water would puddle on it for a surprizing amount of time. The sand sold for baby play areas has a similar particle size and will not breathe, especially in a pot.

Construction sand has larger particles and can be used as part of a planter mix along with something that will hold water. A mix of 50% construction sand and 50% compost makes a decent, cheap mix for some cacti and succulents. Sometimes I have used 2/3 sand and 1/3 compost. These cheap mixes really come in handy when you are doing an outdoor planter or very large pots. The more coarse sand the more drainage, the more organic matter the more water retention. You pick a mix that you think will work for a particular species. Desert cactus lean more to the sand, agaves and succulents lean more to the compost, but it is all species-specific.

For the plants I am doing now (epis) I run the construction sand thru a window screen and only use the coarse part. This coarse sand is mixed with other coarse materials to get a generic orchid/bromeiliad/epi mix for my purposes.

Next up is pea gravel or 1/2 inch minus construction gravel. If you run the construction gravel thru a 3/16th or 1/4 inch screen you get very coarse aggregate.

Where I currently live modern nursery materails are not available and I usually buy construction materials by the yard or by the truck for construction on the house, so this system works for me. A little labor intensive, but works for me in my situation.

[iann]

Blow sand is particularly bad for drainage because it contains a whole range of particle sizes. For good drainage, pick one size. Big enough to create sufficient drainage and maintain air, small enough to hold a bit of water and not leave the roots in big gaps. In a pot, that's at least an eighth inch, ideally about a quarter inch (plus some "soil"). In the ground it is smaller, even down to quite fine sand so long as it doesn't include fines.

In a pot, use sufficient aggregate that the pieces can touch eachother. If they are completely separated from eachother by soil then you might as well not have bothered. You can test for this by seeing how "squashable" a pot of your mix is. If you can squash it down by pushing another pot on top then it doesn't have enough aggregate. If it is fairly firm then you have enough. If it is completely solid then you might have too much

[CactusFanDan]

If it is completely solid then you might have too much

Too much aggregate? Is that such a bad thing? I guess it depends on your aggregate, plants and climate. So many variables! I guess that's what makes it so fun!

[iann]

If it is completely solid then you might have too much

Too much aggregate? Is that such a bad thing? I guess it depends on your aggregate, plants and climate. So many variables! I guess that's what makes it so fun!

I said "might" Still, if it is completely solid then there is insufficient soil and you are going to run into issues. People have found ways to work with those issues, but it is generally much simpler just to have some soil.