Leeks - an A to Z on sowing and growing
There are two ways of growing leeks. The first is the traditional method of buying seeds in the autumn and sowing indoors at the end of December with germination taking place in January, growing into small plants by the Spring time. However the disadvantage we have in Helensburgh is our climate and quite simply the season is too short. The plants are really getting into their stride and it is Autumn and they aren’t going to grow anymore. This method is fine for producing lots of small to medium sized leeks.
However if you prefer to grow larger leeks, there is another method that I was introduced to by some members of the Society many years ago and it is this method I am going to attempt to explain. It is difficult to know where the year begins as it is really a continuous process and has a 2 year cycle. So, lets start by assuming that you have bought a few of the small leek plants that myself or other members of the Society have been growing for the Spring Plant sale!
By this time the plants will be in containers or plant pots about the size of large yoghurt pots and will have been hardened off and be ready for planting out. Ideally the ground where they are to be planted won’t have grown leeks for a couple of years. The soil doesn’t need too much preparation apart from weeding as leeks have very strong roots and will break up most soils. When planting leeks they need a narrow hole that is about 25cm deep and 5cm wide. Something like an old broom handle is ideal for making the holes. The holes should be about 40cm apart, although you can leave a bit more if you have plenty of space and want easier access to the plants later in the season. Place a leek in each hole so that about two thirds is underground and a third left showing above ground.
Once all leeks are planted, water in each plant, filling each hole till it is flooded. Let the water settle for 10 minutes and repeat. At this stage everything looks a bit bedraggled, but that is fine. No need to do anything now for at least a week. If weather is dry, as it often is in May, then water the plants if the ground is very dry.
If weather is dry, water about once a week giving a good soaking to ensure the water is reaching the roots. Weed between the plants if a lot of weeds are growing. No need to worry too much about the small weeds. At this stage, the leeks could be fed, but I do not feed the plants and would not use inorganic fertilizers as I want to eat the produce. If the soil is in good condition (see November) this shouldn’t be necessary. Adding too much feed can also lead to the plants producing lush growth that is susceptible to disease such as rust.
Hopefully the leeks will be putting on good growth. In late July there is an option to “blanch” the leeks which is the term given to making the stem white in colour. Text books sometimes refer to earthing up leeks, but this is a lot of hard work and the soil often falls into the leaves of the plant. With our leeks planted planted deep there will be about 25cm of white stem. Blanching the leeks will not affect the size of the plant, but if the leeks are to be used for exhibition, long white stems are viewed as being desirable.
The easiest way I have found to blanch is to wrap a length of black permeable membrane, the sort that would be used as a weed suppressant round the leek. Cut a piece about 30 x 30cm, wrap around the leek and tie in loosely with string. This creates enough darkness to allow the leek to blanch but breathes enough to prevent the leaves becoming mushy.
Check any leeks that have membrane around them aren’t getting too tight. If that is the case, slacken off the string and retie.
If you are wanting to exhibit the leeks, choose a few that look in good condition and are about same size. They can be harvested the day before exhibition. Give them a wash to remove soil, trim the roots a bit and pull off any outer leaves that are yellowing and weather battered. They are then good to go.
August is also the start of the year for growing leeks! To start the process, you need to select a couple of leeks that have grown well and remember not to send them to the kitchen. If you have exhibited your best leeks, it doesn’t matter, just replant them again and within a day or two. They will be quite happy in the ground and will immediately take root again – it is very difficult to kill leeks!
This is really an important stage of the growing cycle, as these leeks we are putting aside will provide the young plants in about 15 months time. From now onwards I will refer to this as the seed leek.
In September when the leeks are reaching maturity, select a couple of that are in good condition, dig them up and store in an airy cool, dry place, such as rafters of a garage or shed. No need to trim any leaves or roots. Just leave them to dry naturally and any soil will fall off and the leaves will gradually take on a paper like texture.
Check seed leeks in storage are in good condition and aren’t being eaten by mice or other small animals.
This is an ideal time to prepare the ground where next years leeks will be planted. Add either home made compost or well rotted horse manure to the area and lightly dig in. Leaving on the top will also work if you have plenty of worms in your soil.
Check on leek in storage.
This is the time to replant the leeks that you have had in storage. They can be planted in a large pot, about bucket size, about 20cm deep. Water lightly and put in a cold greenhouse or very sheltered part of garden. A conservatory would also be useful as long as there isn’t any heating. At this stage the plant needs light and to be protected from frost.
The seed leeks will now start coming to life. At first the white papery floppy leaves will start to turn green and then the plant will become more upright.
The seed leek can now be put outside and will start growing. A few new leaves will start to appear. Ideally this should be a sheltered location to prevent it blowing over, but doesn’t require full sun, just good light.
In year 2 the guidelines are the same as year 1, but with the following additional steps.
As this is a 2 year process I am afraid you will have to toddle along to the Plant Sale and buy some more leeks. Don’t worry – you might never need to buy leeks again.
The planted seed leek will now be starting to grow very tall as it starts to send up a flower stem. If the pot is dry it will need watering.
The seed leek may need tying to a bamboo cane as it will probably grow to around 150cm tall.
The seed leek will start to grow a flower head.
The seed leek should be in flower, hopefully with lots of small flowers on the head.
If the weather turns very wet and windy, move the seed leek to a more sheltered location, such as a cold greenhouse. The flower head might start to die off a little, but green shoots will have started to appear from the base of the flower. These are the leeks that will be grown on in a couple of months time.
Observe that the green stems on the seed leek get longer.
The flower head on the seed leek should now have long green stems up to 6cm long, which are young leeks, with a small white bulb at their base. Cut the stem and take indoors and lay out on a sheet of newspaper. This next stage can be a little bit fiddly, but just needs a little patience. Each of the small green shoots will need to be removed from the flower head, trying to keep the bulb and green shoot intact. Ideally they will come away quite easily as if left on the plant they would eventually fall off naturally.
Fill a few small seed trays or margarine containers with potting compost. I use ordinary multipurpose with a bit of sharp sand mixed in. Using a dibber that is about pencil size, make small holes about 2cm apart and pop in the young leeks. Firm the soil around the plants and soak the compost with water. A lot of leeks might fall over at this stage, but just push the compost around till they stand up again.
These seedlings now need moving to a cold light place such as a cool greenhouse or conservatory. At this stage they need as much light as possible and ideally frost free. Covering with fleece is usually sufficient, but if it is really cold, then a soil warming cable underneath to the plants will keep the frost away. No additional heat is required.
December and January
Check on newly planted seedlings and keep frost free. If compost becomes dry, water slightly. It is quite likely that a percentage of the leeks will not take root and die. Remove these. There won’t be much growth, but the leeks will be putting down roots.
Hopefully the seedlings will be starting to grow a little and roots emerging from the containers they are planted in. Water lightly and keep frost free.
Seedling will now be growing away quite quickly as the amount of daylight increases and will have 2 or 3 leaves and be about 8cm high. At this stage they will need potting on into individual pots or larger containers, planting about 3 or 4 cm apart.
As the plants grow, start to harden them off by day.
At start of May, providing they have been hardened off they will be ready for planting.
At this stage you will have gone full cycle and be able to propagate and harvest leeks without the need to plant seed.