Growing Offsets

I have several offsets on all my cacti and whilst I will leave many in place because they look nice as a cluster I am looking to increase my stock by removing some of them. What is the best way to do this? What is the best growing medium to us? Do you just sit the baby on top of the growing medium as there is no 'point' that can be partially inserted into the compost? How long is it before roots may grow and hold the baby stable? Any advice will be gratefully received.
Liz

Hi Liz,

Has with a question like this every one has their own way of doing things.
For myself I am always breaking up plants for propagation and the method is quite simple..I remove the offset with either a craft knife or just pull them apart. I treat the base of the offset with hormone rooting powder and then leave in a seed tray to dry off for about a week. Something I forget and they can be there a lot longer and in this case some offsets can show signs of root deveoplment.
The offsets are placed in a tray filled with my standard cactus mix. This is then lefted on the bench and given a light water once a week. Rooting can take place at any time, there is no knowing when.
In some species every offset will take root and in other you will get 1 or 2 at of 20 so be aware of that, other wise have fun and watch your fingers !

Hi Liz. This is what I do - others may have their own preferred way....

I remove those offsets that are really low on the base of the plant. In a while, those lower axils and tubercles will become compacted at the top of the root and any damage will have disappeared.
I usually find that it is best to cut them off with a very sharp knife, like modellers use, with a thin blade to slip right in between the offset and the mother plant so you are only cutting the joining material.
Then I let them dry off for perhaps a couple of weeks, until the cut is properly calloused over, and put them in to a very open compost. I'll try to push the end in a bit if I can. I use my usual mix, with about another 50% of fine grit or sharp sand. I put them into dryish compost, wait another few weeks, and then lightly water from time to time. This seems to prevent any rot, whle giving the developing roots something to get hold of.
How long do they take to root? This is a varibale feast, I have found. Some species take perhaps a year or two - usually the very slow growing species like crucigera or huitzilopochtli - whereas some of the plants like zeilmanniana can take as little as a couple of weeks. It also depends on termperature. I like to give a little bottom heat if my propagator is free, else they go under the bench where it is warm but not in full sun. It is best to start them earlier in the year as well, I have found.

I hope this helps.

Hi Tam and Chris
Thank you for your valuable advice - especially about allowing the offsets to dry prior to planting. I do use chick grit for top dressing my small cacti so I shall add that to my compost mix. I have been reading up about using perlite in cacti compost but I didn't realise that it came in fine, medium and coarse grades as well as hydroponic grade. Can you recommend the best grade for cactus compost please. I do have a heated propagator so that could be used.
Cacti aside, Tam how lucky you are to live on Bute. I have been there several times on holiday with my family during February (avoiding the midges!) and we love it.
Chris I'm afraid that I have not heard of either of those two mammillarias you mention. I am definitely on a steep learning curve and I'm just off to Google them! I expect my mammillarias are the common ones! I will have to list them somewhere.

Morning Liz,

For a compost mix I use equal parts by volume, 1 part soil based No 3 compost, 1 part washed sand and 1 part vermiculite. This is mixed and placed through a 5mm sieve. I do have access to perlite but do not use it has I have found it to be to light and the grains just float away every time you water, leaving a mess under the pot.
Having said that you can only use what you can find locally.
I use this mix for everything, adding more sand and vermiculite for the more choicer species, which before you ask, are far to many to name.

If you ever get the chance to come back to Bute just give me post here and I will be happy to show you around the collection or you could go to the UK Mammillaria Society web-site http://www.cactus-mall.com/mammsoc/ scroll down to the bottom of the home page, left hand side and follow the links.

Liz, just a comment on your use of chicken grit. Often this can be quite alkali, and most cacti prefer a neutral to acid compost. Some limestone in the mix is OK for "white" Mammillarias and Escobarias, as well as Turbinicarpus, and some Ariocarpus. But it is preferable to use horticultural grit for top dressing.
If you wnat to check yours, just put some in the bottom of a glass and add some vinegar. If it fizzes a lot, I wouldnt use it!

Hi Chris
Thanks for the advice however I had researched the best grit to use and deliberately bought guaranteed lime free (no oyster shell) chick grit. Just to be on the safe side I have done the vinegar test and it did not fizz at all and I also carried out a pH test on it and it read at 6.5. Just slightly acidic bordering on neutral. I do only use the chick grit around my teeny weeny cacti as the horticultural grit looks like giant boulders but I will avoid using it in the compost. Is ericaceous compost too acidic for cacti if I am making my own compost up?
Thanks again
Liz

just up at the glasshouse today and found that a young plant of marcosii RS 547 had lost its roots, either via rot or scarid fly but, has you can see the remaining head has started to produce new roots.

Goodness me Tam. Is this something you have seen before and how do you now treat the plant? Will you just cover it over with the compost as you cannot turn it upside down? Can you recommend any small/miniature mammillarias that can withstand an amateur, as I would like to build up my collection. How can I stop that sciarid fly from attacking my cacti?

Don't use a compost with peat in it, Liz, and the sciara fly won't trouble you.

If you are going to grow cacti you will have some of your plants lose their roots from time to time from either Scarid fly or over watering, that's just nature.

If its from over watering you can follow the process has I've set out above to root them back down.

In regard to Scarid Fly: I don't use peat , only a soil based compost, but I do not believe it makes any different. The Scarid fly will lay there eggs where there organic matter.
The important thing, I find, is to let the compost dry out for 4 - 5 days between waterings.

Hi Chris and Tam
I still haven't really had a reply to my question about ericaceous compost as one of the ingredients for cactus compost. I am enjoying watching all my various cacti flowering at the moment (not all mammillarias) and I am hoping to eventually upload pictures of my mammillarias to the forum. I have a further question about the names of mammillarias. I have a cactus which was labelled as Mammillaria polythele var nuda but when I looked this up on the internet it showed a cactus with a few spines and mine does not have any spines at all. Further research later I found a picture looking very similar to my plant and it was labelled Mammillaria polythele var. nudum. What I want to know is are these two cacti the same but with slight differences or are they two separate plants?
Thank you
Liz

Hi Liz,

As a non-Latinist I really do not know whether one should write 'nuda' or 'nudum'. Whatever it is, they are the same. Some other synonyms for the same nearly spineless plant are (I found them on the internet):
M. polythele fa. inermis, M. polythele "sin pico", M. hidalgensis var. tulensis, M. tulosa, M. stachellos var. tulosa, M. hidalgensis var. stachellos, M. tulensis var. stachellos (stachellos is German for 'without spines'). This plant has no spines or just a few rather short spines. It flowers well with small red flowers.
On sciariad flies: From my past experience they really love peat (especially when it is wet), they do not like pure mineral substrates like pumice, possibly because it is difficult for the larvae to dig into it. Since I grow my seedlings in pure pumice I hardly have problems with sciariad flies killing the seedlings, especially not when the soil dries out between waterings (as Tam also wrote).

Wolter.

Apologies, Liz for not responding on erinaceus compost.

There is quite of lot of discussion going on at the moment about how important it is to have an acid or an alkaline compost. It gets quite complicated, with lots of chemistry and reactions being quoted.

All I can really say is from experience. I have used both erinaceous compst and normal John Innes #2. Both have worked fine in my usual mix of 1/3 compost, 1/3 grit and 1/3 bims or cat lit or terramol. However I have always watered with rain water, as there seems ot be a view that while there are some plants that hate an alkali soil, what kills plants quickest is a build up of base salts contained in tap water, unless you are very lucky and live somewhere where all the water comes from granite.

You may find some people that swear that to put some limestone in the compost for white spined Mammillarias, Turbinicarpus, Escobaria because that is what they grow on in habitat. I haven't done scientific tests, and there are also many people who say it isn't necessary.

South American plants, like Rebutias, Gymnocalyciums, and the like appear to prefer an acid soil, so maybe erinaceous soil would be better here.

I'm sorry that there is no simple answer - but I'd use rainwater as my first preference, and not worry too much about the soil mix, apart from making sure it is very porous. I have put in 3 rain butts since I started growing seriously!

Now to Mammillaria polythele var nudum - I think thats the right way to spell it, but it is the same as nuda. As you say it is supposed not to have any spines, but sometimes it does. I'm afraid that its another case of plants refusing to fit into the boxes that we make for them when we name them. Many plants, and Mammillarias and other cacti are no different in this respect, are inherently variable. What has happened is that Mammillaria polythele (a variable species) has thrown up a sport with no or very few or short spines. This probably happens in nature, though I haven;t heard of any field collections of this, so suspect that it is limited, probably because without spines it gets eaten by goats or sheep. When it happens in cultivation, we humans see it as being different from the "standard" form, and give it a variety or form name. I don't know if there is some minor change in chromosomes or DNA, but not enough to make it a different species. Anyway, when the selected plant reproduces, there is no guarantee that the resulting seedlings will be an exact clone of the parent plant. It is a variable species, so you will get variations, even with this selected plant.

Sorry to ramble on, but I hope youy get the gist of what I am on about

Hi Wolter and Chris
I must apologise as I do not yet know how to reply individually to people - need a lesson! Your comments have been gratefully received and another puzzle has been solved for me. My collection is growing almost daily and I love researching all the different types of mammillarias. Following your's and Tam's earlier advice Chris, I have used a non peat compost mixed with coarse grit, perlite and/or coarse sand. I always use rainwater to water my cacti and I keep it inside the house or greenhouse so that it is the right ambient temperature for them.
I notice on the internet that many cacti enthusiasts mention habitat data and numbered forms. Is this just to identify where different types of cacti are found? I also find it rather alrming tht many cacti are listed on the CITES database. Is it known whether these plants are being reintroduced to their habitats at all? I'm just curious.
Wolter it was so nice of you to post a reply too. Maybe you can tell me how to reply o individuals as I am still learning!
Cheers
Liz

I usually use dry way of rooting the offsets. Put them on the sand at shadow with some sprinkling but not watering until roots appear. Some offsets have roots before cutting off, others will need more time - a year before I quit waiting especially if the cut surface become too hard and whole thing hopeless. During the growing season and when it is warm rooting takes not long time, just some weeks.

I must apologise to you Liz. I didn;t se eyour last posting here.

Regarding habitat data and field numbers, you are right that it tells us amateurs where the plants were originally collected. Thr next question really is why is this important? to which I would say that the majority of plants in amateurs collections, especially those who don't specilaise, are probably from just a few collections and as such are not truly representative of the species.

The CITES database does say that some cacti are extinct in their original habitats. Whether reintroduction is possible depends on the wiil of the country, the location itself as it might have bene built upon and finding another for some speciliased plants may not be successful. The reality for Mammillarias is that despite some work by amateurs and academics, the population continues to expand, and this pressure outweighs almost all other factors, and has many consequences - power generation, refuse disposal, roads, agriculture....

If you wnat to reply to individuals, then use the pm (private message) function.