A Northumberland Alpine Gardener's Diary
This entry: 11 August 2014 by John Richards
Northumberland Diary. Entry 280. Daphne grafts.
I am not on the whole the most technical of growers, and the more arcane procedures of automated control or sterile culture are well beyond me. However, I have been making occasional daphne grafts with some success for more than a decade, and having just undertaken another batch I thought I would write about it.
Daphne grafting is useful for several reasons. The most obvious is that I, anyway, find it a much more reliable way of propagating daphnes than by cuttings. I can and do grow daphnes from seed (remove the flesh and soak for 24 hours in dilute detergent before sowing), but for most the problem is acquiring the seed in the first place. Most of the excellent hybrids never set seed (and if they did the offspring would differ from the parent), and many of the species rarely set seed in cultivation, perhaps because they are self-incompatible and require pollen from another genetic individual for seed to set. Two more reasons are that daphne grafts usually grow faster than seedlings or rooted cuttings, especially for the slower species; and they have a head start as they acquire an established and relatively mature root system. In some cases, too, it may be the only realistic way of growing the species at all. I have found Daphne sojaki almost ungrowable on its own roots, but manageable when grafted.
The main snag with grafting is that it requires a measure of forward planning, as it is necessary to sow seed of the stock plants a year before they will be needed. Up till now I had made no grafts for two years, due to an absence of suitable stocks, but last summer I sowed a lot of Daphne mezereum seed harvested from my senescent plant. This germinated well in March, and I potted on more than 30 seedlings in April. These are now in an excellent condition to act as stocks. The deciduous D. mezereum is a less satisfactory host than an evergreen species such as D. retusa, but I do have several successful plants grafted on D. mezereum. My D. retusa has finally set a good crop of berries this year, so I should have that species available next summer (memo to self, sow D. retusa today!).
Once you have the seedling stocks, all one needs is a sharp knife such as scalpel or small stanley knife, and blutack (and of course the source of the scions, the plant you want to propagate). One is supposed to sterilize the knife blade between cuts, but I never bother and don't think it makes a difference (of course it would if one suspected a scion was virused).
Here, yesterday, was everything set out on a garden table and ready to go.
The source of the scions here is Daphne calcicola, a wonderful present from Cyril Lafong last autumn. Planted in a pot in the alpine house, this has grown well, but is rather leggy. Thinking that it needed a prune to make it branch and make a better shape, I realised that the prunings would make excellent scions, which is what prompted the grafting session. Here is one of the prunings, alongside a stock seedling.
Note that the stem diameter of the scion and the stock is fairly similar. It is important that the scion is not thicker than the stock.
The next step is to decapitate the stock, about one cm from the ground, and to bisect the stump for about 3-4 mm. This is the hardest bit, as the vertical cut must go down the centre of the stump.
Here is the bisected stump. The two small leaves below the cut were excised later
The next stage is to use the scalpel to pare down the scion base into a sharp point (two sides of the stem only) so that phloem tissue is exposed on both sides. The v-shaped point is now inserted into the cut in the stock.
The join is now wrapped in a thin piece of blutack.
Here, after eight scions were taken, is the Daphne calcicola, neatly pruned.
Next was my mature plant of Daphne sojaki. This is the plant discovered on Vermion by the MESE expedition and informally named 'D. vermionica' before Halda jumped in and named it before we could. As I said earlier, I find this difficult on its own roots (although I still have four seedlings from my own seed; they scarcely grow) and the current plant was collected on Vermion as a scion in 2008 and grafted onto a D. tangutica seedling. It flowers and fruits well. The annual growth is not great, so there was relatively little material for propagation, but I was able to take four scions. Here is the plant.
And here is the scion inserted.
Another Daphne I had originally introduced from wild scions grafted (onto D. mezereum this time) was D. petraea from above Lake Garda (Nota Pass). In fact there are two of them, withg quite different habits, but one (which I have called 'Pinnochio' from its long 'nose') is budded on every shoot, so I have not disturbed it. The other has a looser habit, with some branchlets positively geotropic, and this is the one that had some suitable scion material. Here is the plant, followed by a scion inserted.
Finally, one of my favourite daphnes is D. x whiteorum 'Beauworth', a D. jasminea x D. petraea cross. This flowered particularly well last spring, and has made a large plant which offers quite a lot of graft material.
In total I made 16 grafts, and here they all are in trays, ready to go into the alpine house in a shady place. Later I might put a propagator lid on them, but at present I am happy with the level of humidity as they settle down. I shall know which have taken when they put on new growth, some in the autumn and some next spring. On past evidence I would hope for about 80% success.
In the meantime, about 12 stock seedlings await treatment, so I might have another go in a few days time.
The day after I wrote this I was looking out of the conservatory window and spotted a Daphne mezereum seedling growing amongst the Satureja parnassica mats.. Fortuitously, something had nipped the terminal bud so that it had branched two forks. Quick as a flash I was out with the stanley knife and blutack. Two more bits were snipped off the Daphne 'Beauworth', the seedling beheaded, and with a bit of luck I shall have a 'Beauworth' growing outside. The search is now on for more self-sown seedlings........