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Re: Grevillea cuttings

I don't think anyone's replied to Jim Mann-Taylor's query about getting
grevillea cuttings to root (apologies if anyone has and I've missed it:
we've been operating a new machine and a new mail system for the past couple
of weeks, with the predictable chaotic results). I asked Jeff Irons of the
UK Australasian Plant Society (and co-author of "Australasian Plants in the
UK and Europe") about this. What follows is the gist of his
characteristically thorough and helpful reply. I'm sending it to the list
rather than to Jim individually, in case it may be of use to someone else as
well (though it's really aimed at UK growers specifically).

1. Cutting mix. Jeff says that British growers often use mixes which are
insufficiently aerated (particularly in mist units). Jeff uses 1 peat: 1
perlite in an ordinary propagator, 1 peat: 3 perlite in a mist unit.
2. Acidity. Grevillea grow best in a low acidity compost. Jeff's found 1
peat: 1 perlite works best and reasons that the alkaline vermiculite
counterbalances the acidity of the peat.
3. Cutting origins. Try cuttings from different parts of the plant. Thin
cuttings from low down on the plant have a favourable shoot:leaf ratio.
4. Cutting age. Try the whip test: bend the tip down to touch the base; if
it springs back it's fine; if it breaks, it's too old; if it doesn't spring
back quickly, it's too young and soft.
5. Hygiene. Dip cuttings in dilute hypochlorite before preparation.
6. Preparation. Cut away bark on two opposite sides of the cutting. Leave as
many leaves on as possible. (This surprises me. Jeff didn't explain why it's
desirable. I usually strip as many leaves as I can. Anyone have any theories
as to why you don't do that with grevilleas?)
7. Hormone rooting gel. Jeff thinks it helps. If you're using a liquid, try
various strengths from 500ppm upwards.
8. Timing. Optimum time in the UK is between the end of January and the end
of March. Then rooted cuttings have all summer to grow on after potting.
(Was that the sound of a hollow laugh I heard, Jim?!) If for some reason you
have to or want to take cuttings in autumn, give them artificial light to
extend the day to 12-15 hours.

After all of which Jeff says that some grevillea spp just are very
difficult. He's failed with G. pachylostyla and G. willisii. Ness Botanic
Garden has failed with G. iaspicula.

Jim: Jeff said that if you want to discuss any of this with him, give him a
ring on 0151-342-1703.
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