Cactus Compost

[Phil_SK]

John Innes is fatal, in my experience. I've learnt the hard way how important it is for me to strip it off the roots of plants I've bought. All of which goes to show that much of our success is down to our familiarity with what we use and how we adapt our watering regimes etc. to our soil mixes.

[DaveW]

Like it or not Ian Levington probably did more scientific research on growing cacti in peat based composts than you or I will ever do, or could even afford to on the commercial scale they do. What most of us agree is simply WE cannot get on with peat based composts for Succulents using our present growing methods, but the Continental nurserymen prove they can be grown successfully in it or it would not be profitable and they too would be growing in something akin to John Innes in preference.

Maybe their methods of growing cacti are different to ours, but people would not be buying cacti from Continental growers using peat based composts if they were not cheaper and often better grown to that stage than we often get over here? When you see Continental collections I don't think there is much the Brits can teach them about growing plants, but a lot we all could learn from them?

It would be interesting to hear from somebody on the Continent the techniques their nurserymen use for growing in peat based composts, how they re-wet it after a winter rest? Do they in fact rest the plants in winter or just keep them moist and growing year round and is the peat just there for holding the plants roots and it is regular feeding responsible for the rapid growth they apparently get, something we can only envy. Remember the plants with dry peat around the roots we buy are after they have been in the retailers hands for a while. Was the peat dry when the grower originally shipped them?

As said, people have always been dogmatic that the current compost fad is the only way plants can be grown. I doubt many of us still grow our plants in the same composts we used when we started growing them? Come back in another 10 years Ian and I doubt we will be using the mixes we do now and will be equally dogmatic that the methods we used today were the wrong ones, that's human nature!

[Rob Kitching]

Thank you all for your comments which I found most interesting. I can't agree with some of them, and my initial post is referring only to the Multipurpose peat/All Purpose peat composts which I have found so difficult, and which seem to be recommended by many nurseries as a growing medium for cacti. Dave, thanks for that UC recipe, I might try that one out. I am particularly interested in cactus composts and though it is clearly lead balloon territory, I, at least, would love to see growing medium and other relevant cultural information included with every plant photograph posted on the bcss forum pages.

Rob K.

[ralphrmartin]

I, at least, would love to see growing medium and other relevant cultural information included with every plant photograph posted on the bcss forum pages.

What works well for someone in a greenhouse in sunny East Anglia is unlikely to work for someone on a windowsill in wet Wales, I'm afraid, and even less so for members in other countries.

I've tried following the Mesemb Society's advice on winter rests for various mesembs, and well, mine seem to want to grow at quite different times to those given, for example. That's probably because it is so humid here even in winter.

In the end I suspect the search for the perfect compost and culture is a bit like chasing the Holy Grail (and yes, BCSS members do remind me of the Monty Python cast).

[Eric Williams]

Very interesting and I think this one could run and and run. Myself I am on Ralph's side here. Composts hold up the plant for it to be fed and watered. Whatever compost is used, if there is no feed, or water the inevitable will happen. Cheers ps. on the peat composts used by the continentals, I wonder if they are grown in another compost, but shipped in peat as it is lighter therefore cheaper postage ?

[Martin]

This is an interesting thread and I think it was Dave who said we are probably not using the same compost we did years ago.

Funny he should say that as on reflection I think am very nearly am!

Way back when I started my local mentor who gave me most of my first plants and used to work with my father used a modified JI No 2 using a granular fired clay material he used to get from the works garage which was used for soaking up spilled oil called "floordry"

So I used the same for a few years and did quite well then I was unable to get the floordry and ended up using Levington which I very quickly did not get on with so moved to a coir base which was better than Levington in some ways as it re wet after winter

It was not good for larger plants over longer periods as I found it degraded and plants stopped growing even with feeding I suspect this was probably pH related now but that's just a guess

Anyway back to the past few years and I am back to JI and now using cat litter which is remarkable similar to that old floordry material I used about 35 years ago !

The only issue now as many have said before if finding good consistent JI, the one that's been ok the past few years Westland is now as bad as the rest from the bags I got a few weeks back

So what next ? At the recent Oxford branch auction Graham Charles found a book in our sales box from the 1950's for 1 pound picked it up said how good it was and very kindly let me have it as he had it already

Its Frans Buxbaum Cactus Culture based on biology, I am still reading it but I think its one of the nest books on culture I have ever read and see why Graham thought so highly of it.

So whats the connection well basically simply put no matter what the compost so long as it provided the right balanced environment for the plants in rough alignment with that species needs it will likely grow.

And as also said above growing in pots is very different to nature so whenever the mix in the pot at the start and no matter what the compost base when its chemistry alters to a point that is unsuitable to the plant it stops growing

I just think based on our local conditions and practices that point in time varies for us all across the different potting media

So conclusion .... find what works for you and don't worry about others options apart from those species you can not grow then keep looking for the right combination !

[3bears]

i agree with dave and ralph here. compost is a highly controversial subject, while many different ones work well. my current fav is about 3/4 perlite and 1/4 fine vermiculite. sometime i substitute commercial peat based potting soil for the vermiculite. this produces an extremely light airy mix which drains rapidly, doesn't clump and lightens the trays so they don't break in my hand when i pick them up. i was adding ground limestone, but some researchers showed it is actually detrimental, as plant growth in habitat was shown to occur while the rain water was acid. i have also read nutrients become unavailable to the plants above pH 6.0.
as to the chicken grits, sand, pea gravels, they are much too heavy, and sandy mixes can harden up when dry. i would add some heavy grit for support when potting up top heavy plants.