Growing for Show - Vegetative Propagation of Blanch Leeks by John Trim

John Trim

Visitors to the top shows are often amazed at the quality of the blanch leeks, but it comes as something of a surprise to most of them that the leeks are not grown from seed but by a process called vegetative propagation.

What is Vegetative Propagation?

Vegetative propagation is used by exhibitors to maintain a particular strain of leek. These strains have been hybridised and perfected by expert amateurs over many years. By vegetative propagation the strain is kept true to the original. It is rather like taking a cutting from a plant and growing it on.

The cutting will be a carbon copy of the parent. When growing for show this has obvious advantages to the exhibitor for as well as having all the good qualities of the parent plant it also becomes much easier to match the leeks for uniformity.

One of the best ways is to obtain a leek from an exhibitor at a show. A couple of leeks from a top grower will give you an excellent start. ‘Never be afraid to ask’

The Method. Cut off 150mm of the leek barrel including the root plate. Trim the root down to 10mm then pop the prepared section into a bucket of disinfectant for 20 minutes. I use a tablespoon of Jeyes Fluid added to 4.5 litres of water. [Editor's Note: This is not an approved use under EU regulations and we are not suggesting you do it]

Select a 20 litre flower pot and fill with a good soil based compost such as John Innes No 3.

Dibber a hole and insert the leek to half it’s depth. Within a week the leek will begin to put up new leaf growth.

As long as the weather is not too severe the leek can remain outside in a sheltered position.

By May the following year the leek will throw a seed spike. These can grow quite tall so will need staking and tying in. The seed head will flower anytime from June into July.

On the 1st of August cut all the flower stalks including the seed from the head, in effect giving it a crew cut. The leek is now bereft of all it’s seed and will respond by producing mini leeks on the head which is commonly called grass.

The seed head must be well supported at this time as we shall try to maintain the head of grass on the spike as long as possible. You will probably find by October that the stem has started to rot through.An indication of this is when the grass starts to wilt on the head.

Now is the time to cut off the head maintaining as much of the stem as possible. Stand the stem in a bottle of water which must be changed every three days. If you don’t you will find the stem will become a mush and the grass will wilt.

Every week check the bottom of the stem, if it is soft or mushy trim it back to healthy stem. The object is to maintain the head as long as possible before cutting and potting up the grass.

Be guided by the condition of the head. If it starts to wilt or the young grass begins to die back then cut off the head flush with the top of the seed spike. Stand it in a saucer of water for two days in good light. The mini leeks will start to root. After two days cut the head in half with a knife and you will find the young leeks will pull away quite easily from the head.

Pot them into individual plugs using a good seed compost. Levington F2s is my preference. The leeks can now be left to tick along in a cold greenhouse until 1st November when the heat goes on and the serious growing begins.

If you are interested in entering or visiting a horticultural show, there is a list of them on the National Vegetable Society web site here: Horticultural Shows