My girlfriend brought this home yesterday, wondering what I should do with it. Any suggestions?

How long is it?

Depending on the length I would do 1 of two things with it.
1) Cut it in half and let it heal and callouse over. Then plant both pieces either vertically or horizontally as logs. If vertically, make sure it's planted with the proper end up. I have seen some people screw this up when the cutting does not have a tip like that.

2) If it's a shorter cutting, I would just plant it as one piece and let it grow.

I know the want to experience the cactus spirit may be overwhelming, and by having a cutting you probably just want to do just that, but think of how many more experiences you could have if you keep growing and cloning that cutting. That one cutting, if taken care of properly, could transform into a massive cactus garden.

It's about 1 1/2 ft and one end is slightly rotten, i was more interested in planting it. What would be the best way to plant it as a log?

Yeah if thats the case, cut off the rotten end, let it dry out for a couple of weeks until the wound has gone woody.

Probably not worth planting horizontally unless you are putting it into the ground, as you most likely wont have a pot wide enough. Either way, I am pretty sure that with logs, you just lay it horizontally and bury 75% of it in a soil mix as I will list below.

Since its a mid-section, you could almost cut it in half too and plant both, as the only way this is going to grow is from new pups at the tip end. The shaft isn't going to grow in height any more. Double your plants! You could try one as a log and one vertically.

If you plant vertically you can do the following:
Buy
- cacti soil mix
- perlite
- propagation sand
(some people use only sand for getting roots to grow, but I use this combo)

Mix these together, almost 1:1:1 for good drainage, even let the mix dry a bit if the soil is too damp - you dont want to cause rot.

Plant your cutting, making sure the correct end is up - if you are unsure we can help, just take a closer photo of the spines. I plant them a little deeper than usual.

If you are in the southern hemisphere and its warm, leave this outside in a shady but bright area for a month or two. A light watering every couple of weeks. I'm not sure what to do in Northern Hemisphere winter. A good spot is where the ground gets warm. I put mine on the brick floor against a wall - it gets nice and hot.
Never check for roots by taking out the cutting as you will break any young roots.

Being a mid-section, your cutting will end up growing a pup or two from the tip end, more if you are lucky.

You can tell when it's strongly rooted when you can pick the whole pot up off the ground by hanging onto the cactus only.

Sorry if this is TMI - im bored!

Thanks man, just enough information. im in Hawaii, so it shouldn't be too hard to get it to grow. Plenty of sun. Can I root them in a pot and carefully transplant them to the ground when ready?

Nice place to grow plants! Lucky

yeah I'm about to put my first ones into the garden bed too and I would expect that would be the safest way to plant them.

Get them rooting in a smaller pot (if you like), once you can pick it up by the cactus you know it is strongly rooted, and probably root bound, that would be the time to transfer them to earth.

I'm looking forward to planting mine, I hear they love the open soil

Id imagine so, I've seen a few growing in the ground that were massive!

Rectangular planters are fine for log plantings.

Lucky you that you can plant in the ground! It'll be much more likely to flower that way.

Consensus is that growing from seed makes for a quicker way of propagating a large cactus garden so getting it to flower ASAP might be worth considering as a worthwhile goal.

Thanks for all the great advice! Cant wait to start my own strain and get some pretty crystals from these babys. Do you think cactus like to drink Ormes/monotomic elements as much as other plants?