Vegetative cuttings

Unit 2 of the RHS Certificate in Horticulture deals with plant propagation. I’ve spent some book-time recently reading about the relative merits of propagating from seed vs vegetative cuttings, learning about basic techniques of leaf cuttings, stem cuttings, root cuttings and layering, and trying to get my head round grafting and budding.

This week at Abriachan I was accorded the honour of taking and potting up some hardwood stem cuttings. I consider this something of a privilege since selling young plants from the garden is quite a substantial part of the business, so not something to get wrong.

We took stem cuttings from various willows (Salix x boydii, S. helvetica, S. hylematica, S. nakamurana var. yezoalpina, S. lanata Stuartii), Forsythia ‘Linwood’, Exochorda x macrantha ‘The Bride’, Weigela ‘Foliis Purpureis’, Cotoneaster horizontalis. We discovered that the leaves of Salix hylematica smell of honey and vanilla when turning yellow – additional notes for the sales bench. I also potted up a tray of Chiastophyllum oppositifolium (a spreading rhizomatous, evergreen perennial) for bringing on in polytunnel 1.

I learned a lot about the ‘right’ way to do things according to the textbooks from the ‘practical’ way of doing things – literally – on the ground.

Timing – the ‘right’ time to take hardwood stem cuttings is when the plant has lost most of its leaves and is dormant. In practice, in this part of the world, cuttings can usually be taken from October through to December at the time that most suits the garden and the gardener.

Hormones – the coursebook says to use a commercial rooting preparation of auxin hormones (IBA or NAA). Donald says it’s not worth the bother, and rooting preparations available from garden centres may be of dubious age and usefulness.

Rooting compost – the coursebook talks about the ‘rooting medium’. Donald uses a mixture of peat-based compost, John Innes and perlite. The function of the perlite is to provide space for air and water around the cutting – densely packed compost will not help it to take root.

Pots – we used the Victorian ‘two-pot’ method, placing the cuttings round the rim. The coursebook does not mention this but Don says in his experience it helps. Here are my first two attempts …Double pot method

Viability – Donald wanted about 10 healthy young plants from each of the species we were cutting for sale next season, so we took around 15 or so cuttings from each.

Recording – I’m not sure that the plant names on the labels in the pots are entirely correct and complete, but I have tried to record them correctly and completely here with due reference to the RHS Encyclopedia of Plants and Flowers. I understand and appreciate why correct labelling is so important and how errors can so easily creep in and spread (like Chinese whispers, or Chiastophyllum oppositifolium…)

There was an interesting discussion over the potting bench about the propagation of camellias and magnolias by serpentine layering and air layering using sphagnum moss, which brought life to the texts I’d been reading. Being at Abriachan is really helping me to contextualise the theory in the RHS course, not just by providing actual gardening practice, but also in being around gardeners and talking about plants.

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