cultivating a cactus from cutting

Question

I've recently gotten a san pedro (Echinopsis pachanoi) cutting as a gift. I'm trying to take care of it as good as possible, but I'm not sure if I'm doing it the right way.

The situation is: the cutting has been properly dried after cutting it, to let the wound heal. The wound is dry, and little white roots were even starting to form. It's about 30 cm / 11 inches tall. I've planted it in a pot with relatively dry cactus soil, the cactus is about 5 cm / 2 inches deep (with supports to prevent it from falling over, and it has plenty of room to grow roots). I haven't watered it yet, because over here it's winter now and I heard that these types of cacti don't like to be watered in the winter (or they'll rot).

It is now in a safe place indoors, in its own pot. It doesn't receive a whole lot of sun (because it's winter and my windows face the north), but there's not a whole lot I can do about that unfortunately.

The problems are:

1. I'm kind of worried that the soil will become too dry (and that the microorganisms will die), but then again, I don't want the cactus to rot. So I'm kind of unsure what to do about that.
2. The cactus is showing some discolorations (lighter green spots in its otherwise dark green skin. Some of the spots are swollen and kind of shiny, like bruises. Would this be damage from transportation, or is it sunburn or something else? Should I be worried and what can I do about it?
3. As I said, the cactus is indoors, so it has to deal with my sleep/wake rhythm and my use of indoor lighting. Would this be detrimental to its health (i.e., could I be disturbing its day/night cycle by my use of artificial light)?

So those are my main questions. If you have any other suggestions/recommendations for taking care of my cactus, please let me know, I'm a total novice at taking care of cacti. Also, if you need to see pictures of it to know what I should do, let me know and I'll see if I can upload some.

Answer 1

The main problem with rooting cacti is rot from sitting in wet soil. Water once to settle the soil and do not water again until you see new growth on the growing tip. The spots are probably the skin drying. This is normal. Cactus skin gets brown dry spots on older growth. If the color is more sickly green and the spot is soft then it is probably rot which happens from the inside out. You can save a cutting from rot by removing all infected flesh and allowing it to dry again before replanting. Cacti like lots of sun and heat, but the younger plants can benefit from some shade until well established. During growing season cacti likes plenty of water and will reward you with opulent growth. As the season grows to an end allow the soil to dry and then water only very occasionally during the colder season.

Answer 2

Don't worry about using lights in the room, it will be fine. Typical house lights wouldn't disturb plants. The potting mix would be better if it wasn't bark based but instead pea gravel or even propagating sand. This will ensure good drainage and will still provide enough of a drink. Even cacti need some water. You should water it if you haven't already. Then depending on heating in the house and the potting mix, water every two or three weeks. Bark based potting mixes are terrible in that they tend to become water repellent if allowed to completely dry out. Then you have to soak the pot in a tub for ten minutes so it wets properly and the plant can have a drink.

Leave any re-potting until the plant gets growing though as disturbing the baby roots again might not be so good. Provide as much sunlight as you can. The only real substitute is expensive metal halide lights. No need for any fertilizer or any seaweed etc. By the way if you later switch to a gravely potting mix, it will support the plant much better, without the need for supports or having to plant it deeper than necessary. The mix should only be about two centimetres burying the roots. It is a bit deeper than what they like, which could cause rot if the mix was too moist for extended periods. Not sure if those spots are natural markings or an indication of under or over-watering. Both hydration problems present similarly. In summer take it out to give it plenty of sunshine and fresh air.