Striking or Rooting Blanch Leek Bulbils
2nd Nov 2000
When to Start
Some growers will have already started striking or rooting their blanch leek bulbils or pips hoping to have top quality specimens from next August onwards. Personally I like to start mine slightly later, if at all possible, for the simple reason that nothing stays in prime condition for too long. Starting them off early means that they will arrive at their optimum early and that might not always be the right thing. Once a leek has achieved it's optimum growth, keeping it in pristine condition from that point on is difficult as it will almost certainly lose some of it's sheen.
On the other hand of course we very often have no option simply because the pips or bulbils start to die back on the head and often end up falling off altogether. In such cases it's certainly better to start rooting the pips but at a much slower and cooler rate than normal. You can commence to start them in clean sand inside a cold frame where they will derive no nutrients but purely survive for a short space of time from the small food reserves within the swollen bulb itself.
In the past I have also completely removed heads that have matured too early, sometimes as early as mid August time, and placed them in a paper bag which was left in the salad compartment of the fridge. This prevents the pips from dying off and I have managed to root, under ideal heat and light conditions, pips that had been stored for over two months. Obviously all the above is a mere substitute for the real thing which is to remove fresh green pips with a pure white base.
Striking them into Compost
My bulbils have stayed in reasonable condition this year and I am expecting good results when I strike them into the compost. I have two types of leek to propagate from, my own selection the Welsh seedling and the PC leek which is the one Peter Clark grows so well. The first task is to make sure that the seed trays are all perfectly clean so every one that I shall use will have been washed and scrubbed clean in my long bath at the bottom of the garden using a strong dilution of Armillatox.
The next step is to prepare the rooting medium or compost to receive the bulbils, I shall use Levington F2 to start off the initial rooting process with some added fine Vermiculite; one part Vermiculite to 3 parts F2 will give you a medium that will produce strong early roots. The next step is to prepare the bulbils ready for rooting, this is usually carried out the evening before in the kitchen when every bulbil is removed from the head and each one cleaned up of all dead or dying tissue.
There is nothing worse than finding your rooting pips collapsing in the trays only a few weeks after they have rooted. This can happen as disease spores such as Fusarium and Botrytis enter the plant, usually at the root plate level. It"s very important to minimise this risk as much as possible by first inspecting every head thoroughly for any signs of red spores around the root plate. Good quality pips should be pearly white and showing no signs of corkiness at the root or any softening of the tissues. As an added precaution every bulbil removed from each head is soaked for about five minutes or so in a strong dilution of common household bleach which should kill off all known germs!
Don't be tempted to overcrowd the tray with bulbils, 70 is the maximum that I will root in a single full size seed tray and 35 in a half size one. Another way of starting them off which will ensure that you have a complete root system with every potted on seedling is to use cells. You can purchase plantpak 40's which are 40 thin plastic disposable cells to fit one full sized seed tray. I also use the commercial types which are usually 84 cells in each free standing re-usable unit. Be aware however when using cells that the watering technique has to be correct, every cell is effectively it's own little pot and the roots therefore are incapable of gaining moisture or nutrients from an adjoining cell.
Some bulbils may well not have any green tops on them, just small pea like bulbs, these can be gently pushed into the upper surface of the compost. Other very fresh ones will have long green tops or flags, anything up to five inches tall and are often curved in shape depending on the area of the head that they were developed in. If they grew from the lowers region of the head then they would have to naturally curve and grow upwards on the head in search of light. Plant these with the lower section of the stem being kept upright. The seed tray will initially look very untidy with the flags lying or resting across each other in the tray, they will though soon lift up to give you straight seedlings for potting on.