Picture of Medwyn Williams

Medwyn Williams

Hello. I'm Medwyn Williams – eleven times Gold medal winner at the Chelsea Flower Show, Past Chairman of the Royal Horticultural Society Fruit Vegetable and Herb Committee and President of the National Vegetable Society.

Growing Blanch Leeks


When growing blanch leeks, it’s vitally important when they are potted up into their first pots that they are given some form of support to keep them upright. Keeping the plants upright from a young age means that you are less likely to end up with bent leeks at showing time.

The blanch leeks which were started off from bulbils only a couple of weeks ago are already making excellent growth and standing bolt upright. Most of them were started off in multicell units of 40, ie one thin moulded cell containing 40 individual tiny containers that fit perfectly into one full size seed tray. These are normally sufficient for a month or so and the best leeks are now ready to be moved on into 3 inch pots or Plantpak 15s. These are again made from moulded plastic units but with 15 individual cells for each full size seed tray.


The mixture I use at this stage is similar to the one that I use for potting on the seedling onions and comprises 3 parts of Levington M2 compost, one part soil and one part fine Vermiculite. The soil comes from my actual leek beds and it is sieved through a 1/4″ sieve, When I pot them on at a later stage, I prefer to have the soil sieved through a 1/2″ mesh as the plants love a rougher type of mixture. The reason for using soil and keeping it relatively coarse is to prepare the plants for being planted out into their beds where they will quickly establish themselves. One word of caution; if you intend to use soil, particularly soil from your onion bed, do not be tempted to use it if you have had onions collapse on you in the bed as a result of white rot. Instead, select some good quality soil from your open vegetable patch, soak it with a strong dilution i.e. 1 percent of Armillatox and store it under glass until dry enough for sieving. Be sure to dig the soil up in plenty of time so that the Armillatox has a chance to do its work as well as sufficient time to dry out – the Armillatox will have done the job in approx. 48 hours.


When growing blanch leeks, it’s vitally important when they are potted up into their first pots that they are given some form of support to keep them upright. Keeping the plants upright from a young age means that you are less likely to end up with bent leeks at showing time. I use clips to keep my plants upright and they are made from moulded green plastic which is shaped in a half circle with a groove at both ends to clip into a split green cane. There are two sizes of these clips available and at the young stage you will require the smallest.Push one 12 inch split cane to one side of the leek plant and, just inside the rim of the pot, push one end of the clip firmly on to the cane at a point about three inches above the button. Bring the other end of the clip around the young leek flags and clip it on the same cane just below where you clipped the other end. This means that the leek foliage or flags are encased in a circle about an inch and a half in diameter.

Potting Up

The next important step comes at the next potting stage where you have to be very careful when potting on that you don’t waste time and effort on really badly bent leeks. A young leek that’s up to 1/4″ in diameter can more often than not be worked on between finger thumb until it eventually straightens out. However the problem really gets out of control when the leek is bent at the lowest point on the barrel and when they thicken up. At this stage it”s almost impossible to straighten them without damaging the leek structure causing the internal flags start to come apart within the barrel structure.

The best method is to be very selective at every potting up stage so that you only pot on plants that have perfectly straight barrels. Before potting up, very carefully clear away the compost right down to root or base plate level to have a proper look at the shape of the barrel. The ideal situation is to grow double the quantity that you require, allowing you to be very selective so that you end up at planting time happy in the knowledge that all your leeks had barrels as true as the barrel of a gun.

Another situation can occur later on when, even though the plants in the pots were all upright and straight, the leek can suddenly start to bend close to soil level and at this point there really isn’t a lot you can do. By now, the leek is probably over an inch in diameter and collared up and what has happened is that a fault or disease has attacked the root plate of the leek and destroyed a small section of that root plate. This means that the leek is then being pushed over to one side simply because there are more and stronger roots on one side than the other. This is a phenomenon that can also happen to pot leeks and in the past some growers have tied string around the barrel of leek and attached it to a strong cane which is positioned on the opposite side to the direction in which the leek is bending. The idea is to try and pull it back straight as it is growing. From my experience these leeks are best pulled up and destroyed as the problem is extremely difficult to overcome to show standard.

There is nothing more infuriating than having a gap in a good bed of leeks where one or two leeks may have had to pulled up and destroyed. I now pot up about three blanch leeks right through the growing season (they finally end up in florist buckets) and should I have a failure then these can be planted at any time in the empty station. Even if you don’t have a failure in the row, these leeks are very useful indeed as they can then be kept clean over winter in order to produce pips or bulbils for the following season.


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