how deep to plant

[ItchyBigfoot]

Hi I cut this cactus last fall off of some rotted piece. I let it sit all winter and then when roots showed I planted it. But now roots are coming out of the (I forgot the name of this part of the cactus) and I was wondering should I cut it somewhere else and or repot it deeper so the new roots will be underground. Any advice?

[Aichybatoal]

...What... the... woah. Ok, anyway, the word you're looking for is "areole," the kind of "pad" out of which spines and sometimes fur grow on a cactus. But you've got roots growing out of the areoles... That's got to be the strangest thing I've ever seen! The only possible thing I can think of (and this is pretty unlikely, but it's all I've got) is that maybe the cactus got way too much phosphorous. Sorry if you already know this, but you know how fertilizers have a three-number description, like 2-6-6 or something? It's called an NPK coding, and the first number represents how much nitrogen is in it, the second number is phosphorous, and the third is potassium. Nitrogen promotes tissue growth, phosphorous promotes flowers and a vigorous root system, and potassium promotes disease resistance. I suppose it's possible that your opuntiad got way too much phosphorous, and it's trying to grow roots like crazy. That's pretty unlikely, but it is unfortunately all I can think of.

[ItchyBigfoot]

The strange thing is only this side of the cactus is growing roots. Should I clip them off?

[oldcat61]

That's how opuntias root. You lay the pad flat on the soil & it sends out roots from the areoles. If it already has good roots leave it alone, but if it hasn't rooted well, trying laying it down on that side. Sue

[DaveW]

As Sue says roots do grow from areoles since that's how many cacti root down in habitat. Some Austrocactus for instance grow along the ground rooting down as they grow just like layering strawberry plants. The so called "Creeping Devil", Stenocereus (Machaerocereus) eruca does and often the old part of the stem die off as it goes, with the new part of the stem continually rooting down from stem areoles.

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Possibly the humidity near the soil level has induced it to put out these roots. Some plants however do root better by being laid flat as Sue says with areoles in contact with the soil rather than just relying in roots from the cut surface.

[A. Dean Stock]

Since this Opuntia is putting out new roots it is possible that the potting mix you are using stayed too wet and the roots from the pad in the mix died . If you are using a mix with peat or other organic material , I suggest you repot into a mineral only mix. There are many presented on this site. You might check the roots in the pot. If they appear to be damaged just repot as suggested and you might also include some of the pad that is now growing roots. If you already have it potted up in a good mix, just ignore the new roots.
The rooting of the pad in air also suggests that you have the plant in low light conditions. Opuntia will put out roots on the darker side of the pad in situations with light levels much too low for the plant to grow properly. To grow well, Opuntia need direct sunlight ( or a very good lighting set-up) for at least a few hours a day.
Dean