Scottish Rock Garden Club Forum
General Subjects => Blogs and Diaries => Topic started by: mark smyth on April 27, 2016, 02:54:34 PM
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Ian in last weeks bulb log you cut back Primula marginata ‘Napoleon’. Did you put the cuttings in pure sand?
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Yes, Mark, he did.
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I use silver sand mixed with vermiculite for all my cuttings Mark. Primula so seem to respond to it very well and quickly in my experience
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I've been lucky to have had a very good gritty sand from our builders yard last year. I've just used the last of it and hope they have something of equal quality in stock. Anyway, my point is that I have moved to rooting all my alpine cuttings in nothing but pure gritty sand and it is very successful. A sand with sharp, gritty particles seems to promote the development of a good root system and I suspect that the lack of organics avoids a lot of problems with rot that may occur in compost. It's amazing how long cuttings/plants can stay in a pot of pure sand (not that I recommend such plant torture). I have just potted up some rooted cuttings that I took last autumn, including Primula, Celmisia, Saxifrage, Salix and Rhododendron (which had a super mass of fibrous roots). Be sure to keep the sand moist (not wet). I put the pots in a small covered propagator in a shady place, which maintains moisture levels.
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What percentage of silver sand to vermicilite do you use Chris?
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I use 50 50. The great thing about rooting in sand is its so easy to check if they are rooted, I just gently tug and if they come out I just pop them back in. I don't cover mine but I do keep in a shady spot in the greenhouse and put the tray into a larger tray that has capillary matting in the bottom and that is always kept moist. I've successfully done a wide variety of shrubs as well as my entire diascia collection when I had them. Primula so do very well too. If I'm doing it in late autumn they survive all winter and I pot them up from late Feb onwards. At the moment I'm doing pelargoniums (I leave my pels in the air to form a callus first), Primula marginata and auricula, a couple of alpine silenes, dianthus and more... I'm sure Matt is right about the sharp sand too, just haven't tried it yet. Originally opted for silver sand as its washed and thought it less likely to have any nasties in it but may give it a try now. I already plant right into it in the garden.
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Many thanks for your advice Chris. I will give both yours and Matts a try.
Dave