Monday, 2 April 2018

Bench grafting

While I did do some field grafting and budding at Wisley, I had never done any bench grafting. The opportunity to practise, however has come now, as I am studying to complete my RHS level 3 Diploma in the Principles and Practices of Horticulture, and grafting is an examinable skill.

Grafting is mainly done at the earliest time of spring, just before bud break, and in the late summer, when new wood has had time to ripen stiff enough.

In order to prepare us for the July test of budding and side veneer grafting, we got some training in whip and tongue, which is based on the same basic cut.



The most important requirement for grafting is a sharp knife, without which you have no control of the cut. To sharpen the knife you need a water or oil stone. I have an Arkansas oil stone that is just wide enough. After oiling the stone, you have to place the blade whole on the stone, finding the original sharpening angle of the bevel. You only sharpen the bevelled side of the blade, and you have to get the angle right, or you won't get it sharp.

Finding the sharpening angle
on the bevelled side

Once you settle on the right angle, place the other hand on the tip of the blade and pull towards you, with a steady motion. Then you start again,  repeating for five/six times. It has to be shave-proof!
To finish off, remove the burr on the other side of the blade, by placing it flat on the stone and using gentle round motions.

Once you have a sharp knife, you need to hold your wood safely. I have previously nipped my fingertips and therefore find it easier to wear preventative plasters (namely on the thumb of the knife hand), but we were taught a foolproof way to hold the wood to avoid that.



Hold the wood close to where you are going to make the cut, palm down.







Then grab the blade quite close, to wield control, and you are ready to go.





The basic grafting cut is a sloping cut that leaves you with a flat surface, some 2.5 to 3 cm, across the wood. To achieve that, you have to slide the whole blade, bottom to tip. You start by placing the bottom of the blade on the top side of the wood that you are holding, close to your hand, at some 30 degrees angle, then you pull it towards you, sliding it in the wood towards the bottom and all the way to the tip, like below.


You start with the scion wood (the 'stick' of wood that you have chosen for a specific cultivar of plant that you want to grow - taste, appearance, whatever that is for) and need a clean cut: as flat a surface as you can muster, as it will need to adhere perfectly to the matching cut you are going to make in the rootstock (which you have chosen for the qualities of the roots i.e. disease resistance, dwarfing stock etc). You can tell if the cut is flat when you place it against the blade of the knife.

A flat enough cut

I did practice a few cuts on Cornus stems





Once you are confident on your cut, you can decide to go for it. I have described the procedure for whip and tongue grafting before, so I won't repeat it, but there were a couple of different things in bench grafting, which I noticed.


First, the scion stick is longer, 15-20 cm with at least five buds: you don't risk knocking it off that much at a desk as you do when standing over grafts made in the field. And, because I read in my propagation books that the healing process starts in the scion wood rather than the rootstock, it makes sense to have more wood = more stored energy available.




The other difference is in the tying of the graft union. We used a simple elastic band instead of grafting tape, and we started at the top of the graft going downwards, which is really easy. Again, it makes sense - in the field, you are standing over the graft and if you start at the top, the scion stick is in the way and you keep knocking into it, but here... super easy!

Test whip and tongue on willow
The result of my efforts: 2 Spartan apples
on M9 stock

I went home to pot my new apples up!
The next step, grafting on the plot where 14 rootstock plants await...



Thursday, 1 March 2018

Glass cutting

More panes on the ground than on the frame!

With my newest plot I inherited a rather wrecked glasshouse. I don't seem to have been overexcited about it, as that is pretty much the only picture I took of it, although I did take some pictures of plants around it, and there are pretty daffs!


There's some pretty daffs in front of it

Anyway, during the most recent Christmas holidays, desperate to take my mind off Brexit and have control over something, I thought it would be a good idea to fix it.

I trawled the internet for glass panes, and found that FB marketplace was a pretty good place for it: I got myself a dozen of panes for the price of only a 4-hour round trip.

Oil glass scorer
As the panes were different sizes, I also bought a professional glass scorer. I did not use any oil, as YouTube taught me it was not really necessary.

I also got some W and Z glasshouse clips, my safety glasses, and thus armed I made my way to the plot.

So much glass wasted

The first thing I realised I needed was a very flat surface, clear of debris. Luckily, my falling-apart shed delivered just the perfect laminate board, so I got myself a ruler and started cutting, with mixed success and a lot of frustration.

Anyway, two months on, I finally seem to have cracked it, thanks to random suggestions from peeps on the web and a lot of practice, and I want to share my tips with you, hoping you won't waste as many panes, should you have a go.

Essential tools:
  • a scorer 
  • safety glasses
  • gloves
  • a smooth surface
  • a bucket for fragments
  • a ruler that covers all the length of the cut and is thick enough not to end up between the scorer tip and the metal head, rather help the metal head slide 
  • duck tape
  • pliers (the standard worked ok, but you can get special ones too)

By trial and error, I found the following worked for me:
  • tape the glass inside the part that you want to keep, and score along the side that has to go
  • although you can tape only one side, score both sides
  • use a long enough ruler to go all the way in one smooth score line
  • hold the scorer like a pen; when scoring, try not to stop halfway, and press well: it has to make a jarring scratchy sound as it goes
  • if the side that has to go is 10 cm or larger
    • once you have scored both sides, turn it with the tape side up
    • place a glass strip (or similar), long enough to go all the score line and not too thick, under the tape and aligned with the cut
    • apply equal and gentle pressure with the palms of your hands both sides of the tape and away from it, until the pane snaps (if you are lucky, in one snap and a perfect straight line)
  • if the side that has to go is 10 cm or thinner, there is a high chance the pane will shatter if you apply pressure with your hands: use pliers! If you are lucky and the strip is thin enough, it will come off in one go. Otherwise you have to do it bit by bit.
Ideally, one would sand the cut surfaces too, especially when they are ragged.
I finally managed to do triangles for the roof sides, and that was with great satisfaction!


Both sides that needed cutting were taped, to start with. I was going to score outside the tape (recycled tape so it looks a bit tatty by the third pane, but works).

I used a long fragment of glass (appears in the picture above) as a ruler, placed alongside the tape: you can see that the metal handle is guided by the glass pane in a straight line









Finally, with the taped side up, I grabbed the glass with the pliers, and pulled gently upwards (don't forget to wear your safety glasses while doing that)







And... ta-dah!














Unfortunately, in the process I broke too many panes to finish the glasshouse.

Very luckily, I found more panes, thanks to a chance conversation in the office and a lovely colleague, so I will be at it again soon. 

It's starting to look like a proper GH again

In the meantime, I have tidied up the weedy inside of the glasshouse. I dug two beds, edged them, and topped them with compost, then re-established the middle path, which was flintstones on plastic membrane.

I will have a trained peach on the front bed, underplanted with shallow rooted annuals. At the back (alongside the plot hedge), I want to have a very tall bench for pots, underplanted with annuals. We'll see...

Happy new gardening year to all!