First of all I'd like to thank everyone who helped me out with the Thanksgiving Cactus, and I've already got a small section growing on each plant.

The next job is to repot the Echinopsis, which spends its time either outside or dormant in a cool and not too bright room.

It's a cluster that was bought at a car boot sale when I was ten (15 years ago). Its age at the time was estimated at ten years old, and it was in an 11" pot. It was repotted several years ago by being pulled out of its compost and dropped smartly in some more compost, and recently repotted again as it was literally starting to overflow the pot. At this point it needed to be cut out, and the repotting had to be cut short due to lack of light, equipment, and confidence.

The mix around it is marginally better, but I put far too much sand in it and the compost needs to come away from the roots anyway.

There are two main concerns I have:

1. Keeping the cluster intact. This was not such a problem when it was sitting low in the pot and bound tightly, but now that it's relaxed a little it'll need to be tied together during the repot. I assume that cable ties and towelling will hold it securely, but is there anything else to consider?

2. The consequences of changing the medium from compost to a fast-draining mix. The cactus hasn't been fertilised or watered by human hand for several years, but it still looks fairly healthy and puts out some flowers every year. That to me suggests that there's a whole little ecosystem in the pot (there are certainly centipedes in there), because none of us have been giving it anything.

I'm a little worried that making the change from pure compost to a mostly inorganic mix (bark, perlite, gravel, at about 1:1:1) will somehow kill it with kindness, especially if I make mistakes with the fertilising or damage it during the rootwork. There's no rot anywhere, the skin is firm and evenly coloured, and the only pest problem it has is with slugs and snails. I feel bad about leaving it in such poor housing, but at least it's stable and growing, so I'm not sure what I should do.

Here's the cactus as it is now, propped up with rocks. I've tentatively identified it as an E. chacoana, but it could easily be a hybrid of some sort. For scale, the largest column near the top is 3 inches wide. Also, since then it's been put in the shade so it can heal the mild sunburn on the rib edges.

{{gwi:551657}}

Many thanks -- I really don't want to mess this cactus up.