Is it potted with another plant?

Looks like it is in peaty soil and may be suffering from over-watering. That would make it fall/lean rather than staying erect as it should be. Another reason for leaning could be lack of light and the plant stretching toward source of it, but to get it lean so much it would take a while in exactly same position. I suspect over-watering.

Not potted with anything else, just others nearby. I rotate it often to keep it from leaning towards the sun, so I'm pretty sure thats not it.. I did water it yesterday, but it had already fallen over. Its in a cactus soil mix. The base is very tiny compared to the top.

Stephanie

The base seems to be yellowish, and that also suggests over-watering. Is there a drainage hole in that container?

I really think that soil is very water retentive. It may appear to be dry on surface, but deeper, it remains wet. It takes a while before it start falling over like this - it builds up over time. I see some white deposits on the surface - probably salts from the water that accumulated, or could be mold. Cactus soil mix is advertised as well draining, but unfortunately it isn't most of the times. Succulents need well draining and aerated soil/mix, and peaty mix is not.

I would take the plant out of the container. Get all of the soil off the root ball (see how wet it is closer to the bottom of the pot/container). Check if that yellowish part is soft - not easy to do with cacti, watch the spines! Check the roots: are there any? are they plump and white or light brown color? are they soft-mushy-dark color? are they dry and brittle? If you can, take a photo of the roots and post.

If it actually started rotting, plant may be saved by 'decapitating'. But first, let's see the roots.

I agree totally with Rina. In addition, if the roots are ok re pot In that better mix as above and top the pot with a good layer of horticultural gravel it will help stabilise it, won't hold water so it won't rot it.

Loop a soft cloth or a couple of narrow sheets of newspaper around it and hold the free ends to unpot, clean it and test for softness.

Thanks for your help. The pot does have a hole in the bottom. The soil was moist throughout, but no mold or rot. I rinsed the roots ( hopefully that's not bad) to get a good view. Yellowish part does not seem soft. Let me know if you need a closer view. Also, what soil mix for repotting?

That looks quite good. If there are any damaged roots, you can snip them off. You can leave plant without soil for a bit, hopefully you can get better mix. If you have only this succulent, you could improve your cactus soil by adding perlite (very easy and inexpensive). It would be good if you sift it (cheep kitchen sieve from a dollar store would do :) to get rid of dust. Mix sifted perlite 50/50 with the cactus soil. If you could get hold of grit, it would be even better, mixing grit+perlite in approx. equal amount and adding about 20% of soil (I wouldn't do any more soil, you could do even little less. Your mix will be approx. 40(grit)-40(perlite)-20(soil)%). The grit should be about size of large perlite granules (about aquarium gravel size).

The yellowish low end of your cacti (if not soft) could be either from being originally deeper in the soil (so not receiving light) or it could be (?) beginning of corking - that is a natural process with older plants. It is usually brownish and looks little like dry skin).

Plant cactus into the mix. It may need some support to begin with, you could use layer of grit or even better, few larger rocks.

It should go into best light you can supply. If the source of light is from one point, make sure you rotate pot approx. 1/4 turn every 10days-2 weeks or so. You could use piece of mosquito screening (from old window screens) or coffee filter to prevent washing out thru drainage hole.

For future watering, you could use a bamboo skewer. Insert it deep into soil (1/2 way or more), avoiding root ball. If it comes out damp-cold feeling and/or with small particles sticking to it, there is still plenty of moisture and wait few more days to water. With grittier mix, water should drain out freely. Dump any excess from the saucer.

Thank you so much for your insight and instruction. Do I plant only the roots ( to the base of the cactus)? How deep should the mixture/pot be? Would it help to plant in a tall planter, but 1/2 full of soil so the planter would hold the plant, or would that not provide enough light? Any idea on the name of this species?

Stephanie

Do not plant deep/low inside of the pot. That shades the plant and worse - creates little more humidity around the stem. Planting high, even on a little mound, is better. Bury all the roots and just a little of the stem, rather fill around the stem with gravel, or small rocks (something like pea gravel size-wise) and couple of large rocks for support if necessary. Here is a photo of just repotted succulent with top dressing of gravel and few rocks for support:

It really doesn't need extra deep pot. Using well draining mix, you could have bigger and deeper pot since it is less likely to stay wet, but it is not necessary for the plant.

I believe it is a Trychocereus hybrid - but I am not sure...

Thanks!

Replanted - thanks again for the guidance!