Those succulents will get pretty big, especially if planted in the ground. I have one that's around 15' tall and still growing. Be careful if you trim it. The white "sap" is a very strong irritant -- don't get it in your eyes. I remember rubbing my eyes one time after I had washed my hands, but I guess there was still some present -- my eyes burned for several hours.

This plant roots so easily you cant get it to NOT root. I would take some smaller cuttings, AFTER you lop off that big top cutting, it will sprout out new side stems from where you cut. And yes, the plant in the ground will live and sprout out more side branches where you cut it. You could dig it up and move it, if you wanted! It is indestructable...almost. So,it will make it have a different shape after its haircut! So, decide where you are going to make that big cut. It will fill in with new stems,but it wont be as 'natural' looking for a while, till the new stems come in. I have cut the main stem growth and now I have a big fat bush,instead of a tall lean 'tree'. Mine is the 'Sticks on Fire' variety...with the reddish stems when they first sprout, not the plain green one. And it loves to be pruned. Make sure you have a clean cut to plant,take off any side stems so you have a 1-3in stem to put into the soil. Any soil will work. But a good fast draining soil will work best. 'Top soil' alone will kill it overnight! It will sufficate any roots that try to form, and it will rot.It is a succulent/cactus, so it loves fast draining soil,heat,and sun! You can put some rooting hormone powder on it after it callous' over for a few days before planting it,if you want. But you don't HAVE to. And the part you leave behind will of course live and do well. It will sprout out side branches and probably put out a few new stems that will try to replace the top upright growth. Pick the best one and it will look like it did before in a year or so. You dont have to wear a 'haz-mat' suit when you cut this plant and handle it. The sap CAN be irritating to some people. But it isnt liquid acid, and it wont spray out at you. Just be careful and put on some gloves and eye protection. BUT if you get it on your skin, wash it off with dishsoap or another strong soap. As a precaution, the sap is kind of like touching poison ivy..it will be a little while before you find out if you are or are not allergic to it...if little blisters turn up and if it itches or not. So, just incase, wash good after IF you get sap on you, and just because you have been in the garden of course:) It isn't like the acid blood from Aliens! SOME people get a rash from the sap, and there are a FEW people that are VERY allergic to it and will get hives or blisters on their skin where any sap touches. My mother cut mine pencil tree back once and her hands looked like they were burned for weeks! I have cut it back so many times,I cant count, and the sap has covered my hands and nothing happens to me. So just be careful. Enjoy your new plants,and while they are rooting,IF you can leave them outside in as much warmth and heat as possible, that is great. Inside, put the cuttings in south windows or next to sliding glass doors that get sun through them. They will root VERY easily. The smaller thin stems root faster, but if you root a BIG fat stem,you will get a BIG plant FAST! But it is a bit harder to get it to root,but it will root! Then you have a new BIG plant! Pets should leave them alone. It is poisonous to pets. But IF they take a nip at it...it will only be 1 nip,I think the taste alone will stop them in one nibble. Then the rest of the day, they will try to get rid of the taste! But I think they 'know',not to touch this plant. animals know these things. Good luck,let us know what happens and if you get a big fat plant!

When we first moved into our house about 10 years ago, I was amazed when I came upon a massive pencil cactus growing on the east side of our house under a mature oak tree. No exaggeration-this cactus had to have been about 25' tall and very healthy despite very limited sunlight. Long story short, I read an article warning of the poisonous sap that oozes out of it. Needless to say, I no longer have the cactus. It's a beautiful succulent but just a warning to be very careful around it if there are kids or cats in the neighborhood. I think this is one of those plants that you can totally neglect and it will continue to thrive. Here's a link you may want to check out just to be on the safe side. http://www.arhomeandgarden.org/plantoftheweek/articles/Pencil_Cactus.htm

The water requirements of any indoor cactus is determined the amount of sun light it gets,which you did not mention. Cactus receiving 5,000 foot candles, the measure of light, which is about 1 foot from a south facing window, should be watered every 3-4 weeks. Greater intervals with less light but at least once every 2 months. To adequately moisten/wet the soil in the pot, place the pot in a container with enough water to just cover the pot, allow time for the soil to absorb all the water it can hold, remove from the water and allow to drain. What is most important is the that the soil reach it's maximum water holding capacity.