Poor tap roots on lithops

[Gail]

I had to repot my lithops into a better soil and this time I washed their roots off. All but one has very little tap roots and it almost looks like the fine hair roots are dead. What care should I give them to encourage good root growth? Right now their medium is nearly bone dry, it a mix of play sand, potting soil and perlite.

When I got them, they were in soggy heavy soil.

[CactusFanDan]

Lithops fine roots die off between waterings anyway. As long as the taproot is healthy the plant will regrow the fine roots whenever water comes along. However, play sand is a horrible soil ingredient, so you might want to mix a new batch of soil without it. Play sand is way too fine and blocks up all available air holes in your soil mix (which are extremely important for cacti and succulents alike). I generally avoid adding sand to my mixes, as there's usually sand in topsoil or whatever 'organic' additives I use.

[Gail]

Its the tap roots that aren't very good. They are stunted and bent. I don't really have a option but to use play sand, its the only porous medium they sell around here besides perlite. Its mixed 1-1-1 with sifted potting soil/sand/perlite. I am looking for a course sand, I will replant again if I can find some.

[iann]

The taproot is the only part of the roots that is permanent. Everything else will grow back when it is needed. Not a lot you can do about the taproots now. They establish in the first year or so from seed, then only grow very slowly, mostly getting thicker. If the roots were stunted from birth they'll be stunted more or less for life. Stunted taproots won't support as much fine root growth so the plant will always be at a disadvantage, but usually not a problem with the generous treatment they get in cultivation.

What you can do if the roots are really useless is chop them off and start again. Lithops cuttings will root fairly easily although you sometimes have to be patient. It is also a good way to rejuvenate very old plants.

Play sand is terrible stuff for plant roots. Even Lithops. Lithops don't grow in sand anyway. They grow in broken rocks, sometimes mixed in quite dense clay. If you know what decomposed granite is like, that is a lot like typical Lithops habitat.