The important thing with such heads is to make sure that the root plate of the young bulbils are clean and white with no sign of corkiness or browning, that is a sure sign of disease and though the bulbils might appear to be rooting away they could well collapse after a few weeks as the dampness around the roots spreads the disease further.
I have some excellent heads of leek bulbils this year of the cleaned up Welsh seedling blanch leek that has won so many prizes since it first came on the show scene by Ivor Mace some years ago. The heads are large and clean and I should have no problem with rooting them. The important thing with such heads is to make sure that the root plate of the young bulbils are clean and white with no sign of corkiness or browning, that is a sure sign of disease and though the bulbils might appear to be rooting away they could well collapse after a few weeks as the dampness around the roots spreads the disease further. I also have some top quality heads of my own selection of Peter Clarks leek which has certainly proved to be an outstanding leek and particularly comes to it’s own from late August onwards.
Rooting the Bulbils
Mid November is about the right time for me to root the bulbils as it gives the plants plenty of time to achieve their potential, striking the bulbils any earlier could put you at risk with the plants possibly going to seed during July next year. If the heads are fresh and green and still tight on the stalk, then remove the head close to the cluster with a sharp knife and then push the knife into the upturned stalk in order to slice the head in two. Once you have done this you can then peel the bulbils away individually and commence to root them. If you try to pull them from the head when they are very fresh and tight there is a strong possibility of them snapping off leaving the root plate still attached to the mother plant.
Top Quality Leeks
Bulbils, pips or grass is certainly the easiest and best way of getting top quality leeks, it would be very rare indeed for someone to win at National level with leeks grown from seed against those from bulbils. As the bulbils are removed from the mother head of a leek that had all the right attributes to start with, then the resulting bulbils from that mother head will retain those meritorious attributes as it is in essence a form of vegetative cutting from that plant. As the bulbils can vary in length from an inch to over four inches, the propagation can be very quick and they will need potting on in a matter of a few weeks. With leeks from seed it would be much longer as the seed itself would take upwards of three weeks to germinate and many weeks more before they could be potted on, more importantly they wouldn”t all have the same uniformity either.
Prick out each individual bulbil into a seed tray containing some Levington F2 with a third of added grit to open up the medium and assist the bulbils to throw out strong roots. They must of course be properly looked after from day one and mine will be grown on a propagating bench with some bottom heat of around 70°F and a minimum air temperature of 55°F. They will also be subjected to artificial lights which in my case will come from a Phillips Son T Agro lamp. This is a commercial type lamp with a 400 watt bulb and one lamp will give sufficient light spread to cover my whole bench which is the length of my 12ft greenhouse and three foot wide.
Years ago I used to have some excellent leeks during mid August from bulbils that had been rooted during late November with nothing more that an air temperature of 50°F. In fact six such leeks were awarded the best exhibit in show at the National Vegetable Society Championships in Southport, more years ago than I care to remember by now! Naturally they were not as large as those seen on the bench today, they were probably just over 7 inches around and 18inches to the button whereas now they have to be well over 8 inches around to stand a chance at the highest level. However it does prove the point that there is no absolute need for bottom heat or lights, but if you have got them, the quality and size of the leeks will certainly be improved. Warm fluorescent lights will also do the job provided you have enough of them to maintain top growth.
Fresh bulbils will soon be standing bolt upright in the seed trays and when you are happy that they are really well rooted and growing strongly, you can then start to select the best plants for potting on into three inch pots. When potting on make sure that you pot more than you require so that at future potting on stages you can be really selective picking only those leeks that match each other in size. If you have enough space in your greenhouse then pot on double your needs and only at the final potting stage pot up what you require for the beds plus about 3 spares. These three spares can then be continually potted up into fairly large pots as I have seen a couple of plants of mine collapse later on in the beds for no apparent reason so a spare plant is always better than a gap in the row.
Since I have been introducing soil to the Levington compost as well as some vermiculite at every potting stage, the quality of the plants have improved immensely and with the ratio of more soil to Levington as the pot size increases, the plants are gradually being accustomed to the soil that they will have to grow in eventually. The soil has already been sieved from my leek beds and stored underneath the greenhouse bench so that it is already at the growing temperature. A few days prior to potting, the Levington compost bag will also be brought into the greenhouse. My first potting mixture is as follows : 3 parts of Levington M2, 1 part of sieved soil from the leek bed (soil from the onion bed will also suffice) and 1 part of fine Vermiculite, there is no added fertiliser or soil conditioner required.