S, S, S - Part Seven

[AnTTun]

As I've mentioned in some of my previous posts, when it comes to (hybrid) astrophytum seed, I preffer StarAstrophytum, owned by Roman Pavlica. Excellent service and high prices distinct them from many other seed sellers. Tho, 'high price' is relative, cheap seed with low or 0 germination is the most expensive IMHO.

Anyway, I decided to sow some astros this year, so I got 3 seed packs from them. Astro myriostigma mix (300 seeds), astro asterias mix (300 seeds), astro myriostigma onzuka (100 seeds). And got so called 'Star Astrophytum MIX' as a bonus (100 seeds).

Most astros start germination fast, in 2-3 days after sowing, but some hybrids might take even 10-15 days (had few of these, thought the seed was sterile, almost threw them out). In this case germination started in 3-5 days.

I gave them 2 weeks and then counted, germination ranged between 71% and 91%, averaging at 85%. Since sowing (their) astros is easy, I decided to do lil' experiment too, so I've sown most of the seed on regular soil, and about 10-15% on clay. I was aware there won't be enough seed on clay for exact test but I wasn't ready to risk more.

Results were interesting: 'clay seed' had lower germination results and slower growth than 'soil seed', as you can (hopefully) see. Another interesting thing: I have repotted all the seedlings, moved seed from clay to soil and put the tray back into propagator. And I got more seedlings from ex-clay seed.

Conclusion is: clay is a NO-NO when it comes to sowing astros. Probably other cacti as well.

[Terry S.]

What do you mean by clay? Is this moler, the calcined variety, now much loved by Brits in the guise of cat litter? If so, do you think the difference between the two media is water retention?

[AnTTun]

In my case, clay is what tennis players use. Grounded brick, something like that. I'd say it holds water even better than soil mix, but for some reason seedlings didn't like it. Maybe grains/particles were too big, maybe something else was the cause, I don't know for sure, but I doubt I'll use it again.

Zeolite will be my next experiment when I get enough seed to play with.

[el48tel]

I'm NOT a soil scientist, but my chemical knowledge tells me that clay, fired or otherwise, does much more than hold water and break open the structure of the soil. "Soil" is a dynamic structure; it changes as you add components. Although it has some buffer capacity (i.e. it can nullify small changes because of its composition), it has limits to its capacity. Clays, fired or otherwise, are made from sheets of silicate materials; sitting in between the layers are the metallic components such as potassium, sodium, magnesium, aluminium, calcium, iron, etc and the non-metallics such as nitrates, sulphates, phosphates etc. and water. You can exchange any of these interstitial components by "drowning out" with other components in the water you add, i.e. in the aqueous fertilizer you add; but the ratio of the components is governed by some severe mathematics called equilibrium constants and this leads to a fixed overall composition. Similarly, the organics in the soils a.k.a. peat, tannins etc. can hold components. It's not just those components mentioned above which can be influenced; the acid / alkali balance can be changed by the change in the ratios of the metallic and non-metallic components (it's the hydroxonium and hydroxyl ion balance for the inquisitive reader). Add to this, the atmospheric oxygen reacting with water can increase the alkali component; and the carbon dioxide reacting with water can increase the acid component; at elevated heights in mountains the ratio of the amounts of these changes from sea-level concentrations.
Soil is pretty damned complex stuff; add stuff to it at your peril!

[ralphrmartin]

Antun

I plant my seeds in a purely mineral compost made of sand, grit, vermiculite, perlite and cat litter. I avoid anything organic to try to keep fungi at bay. It seems to work pretty well. They are kept permanently wet (with fertiliser and chinosol added) and very humid.

However, I do note that when I transplant the seedlings into my adult plant compost, 1/3 granite grit, 1/3 coir, and 1/3 Ericaceous John Innes Compost (soil based for lime hating plants), and move them out of the propagator into fresh air, they seem to start growing a lot quicker. I dont think its the extra light. Maybe more carbon is available? I'm not sure. Anyway, the biggest of this years seedlings are perhaps 2cm tall now, and quite a few are 1cm across (including some Astrophytums), while others remain smaller.

Ralph

[iann]

I've always had poor results with calcined clay (hard granules, cat litter). It seems good for cuttings, allows them to be damp without rotting, but doesn't seem to give seeds enough moisture, and the same for growing it doesn't seem to give enough water or nutrients. I know some people do better, so possibly a different watering and fertilising plan would help. Covering the seeds might help too. Maybe not for big cactus seeds, but Lithops seed will germinate in barely moist soil so long as the humidity stays very high.

[Nick_G]

Antun

I plant my seeds in a purely mineral compost made of sand, grit, vermiculite, perlite and cat litter. I avoid anything organic to try to keep fungi at bay. It seems to work pretty well. They are kept permanently wet (with fertiliser and chinosol added) and very humid.

However, I do note that when I transplant the seedlings into my adult plant compost, 1/3 granite grit, 1/3 coir, and 1/3 Ericaceous John Innes Compost (soil based for lime hating plants), and move them out of the propagator into fresh air, they seem to start growing a lot quicker. I dont think its the extra light. Maybe more carbon is available? I'm not sure. Anyway, the biggest of this years seedlings are perhaps 2cm tall now, and quite a few are 1cm across (including some Astrophytums), while others remain smaller.

Ralph

I do the exact opposite Ralph, sow in a JI based mix and then transplant inti a pure mineral mix. We all have our own methods, more than one way to skin a cat and all that. I've tried sowing seeds in pure cat litter but I haven't been very successful. Large seeded species do OK, Pediocactus for example but most others haven't thrived for me, they don't seem to get their roots down in to it and develop very slowly if at all.

[ralphrmartin]

Interesting Nick. So how do you stop everything growing fungi and rotting off in the humid conditions used for seedlings? Do you sterilise your mix somehow before sowing the seeds?

My mix has quite a bit of sand in it, and the vermiculite fairly quickly turns to mush, which presumably gives the roots more chance than the larger particles of cat litter.

Nevertheless, your observation about roots could well be why my seedlings take off when transplanted...

[sechjoh]

I use PP plastic pot and boil them with soil and water in a microwave oven before I sow

[AnTTun]

I did that once Christer. Then Mrs. TT made me clean MW oven, wipe whole kitchen and get automated air freshener to get rid of the stink. Never did that again