How to Grow Leeks From Seedling to Mature Plants
Leeks are one of the most underrated crops in a vegetable garden. They are slow to grow, but they are patient with the gardener. Once they are established, they sit quietly in the bed for months, building a thick white shank underground while their blue-green leaves fan out above the soil.
At Raikana Primary School in Pretoria, we are currently growing our first leek crop on raised beds prepared with chicken feather fertilizer. They are being watered through the heat of the season with our DIY bottle drip system. The plants are still in the ground, still growing, and this article documents the journey so far.
It walks through the full process, from the tiny seedlings we started in small containers to the maturing plants we have in the bed today. If you want to see how the raised beds were fed, I covered that in how to use chicken feather fertilizer in a vegetable garden. And if you want to see the watering system we used to keep them alive through the heat, that is in how to make a DIY bottle drip irrigation system.
In This Article
- Why leeks are worth growing
- Starting leeks from seedlings
- What young leek seedlings look like
- Preparing the seedlings for planting
- Planting leeks in raised beds
- The leek bed and watering
- What a maturing leek looks like
- What to expect as the plants finish growing
- What I have learned from growing leeks so far
Why Leeks Are Worth Growing
Leeks are a cool-season crop, but they handle a range of conditions if they are watered consistently. Unlike onions, which need to be harvested and cured, leeks can be left in the bed for weeks after they are ready. That makes them a very useful crop for gardeners who want a steady supply of fresh greens through the season.
They are also heavy feeders. Leeks need steady nitrogen through the season to build their thick white shanks. This is one of the reasons we planted them on beds prepared with slow-release feather compost, and it is why the watering system we set up was so important through the hot weather.
For us at Raikana, the leek crop has become a reliable presence in the garden through a season when other vegetables are slowing down.
Starting Leeks From Seedlings
Leeks can be grown from seed, but they are slow to germinate and even slower to grow in the early stages. That is why many gardeners start them in containers or nursery beds first, then move them into their final position once they are strong enough to handle it.
We started our leeks in small pots filled with a light compost mix. The seeds were sown thinly, watered gently and kept in a sheltered spot with morning sun and afternoon shade. It took about three weeks before the first thin green shoots appeared.
Once the seedlings were a few centimetres tall, they needed to be lifted out of the pot, separated gently and planted into their final bed. This is the most delicate stage of growing leeks, because the seedlings are fine and the roots tangle easily.
When we lifted our seedlings, we did not separate them one by one. Instead, we lifted the whole clump of soil at once, keeping the root ball intact. This gave us a chance to see the full root system and to handle the seedlings without tearing the roots.
What Young Leek Seedlings Look Like
Young leek seedlings are thin and delicate. In their first few weeks, they look like blades of grass more than vegetables. The stem is barely visible, and the leaves are fine and bright green.
This is the stage where most growers lose seedlings. The plants are fragile, and any disturbance to the roots can set them back. The best approach is to handle them as little as possible and to plant them into soft, well-drained soil as soon as they are ready.
As the seedlings grow, the leaves start to fan out and the stem thickens. What was a thin blade of green becomes a small plant with a visible shank. This transformation takes several weeks, and it is the first sign that the leeks have settled into their new bed.
Preparing the Seedlings for Planting
Before planting, the seedlings need to be separated. This is the most delicate step in the whole process.
We lifted the clump of soil from its pot and gently worked it apart with our fingers. The goal is to free each seedling with its own small root ball, without tearing the roots or snapping the stems.
When the seedlings are separated, they can be trimmed. Some gardeners trim the roots to about 2 to 3cm and the leaves to about 10cm. This reduces transplant shock and encourages the plant to focus its energy on establishing new roots.
We trimmed ours the same way. The roots were shortened slightly, and the leaves were trimmed back so the seedling was not putting too much energy into keeping long leaves alive during the move.
Planting Leeks in Raised Beds
Leeks need a deep, loose bed. The plants grow down into the soil, and the deeper the bed, the longer the white shank will be. Raised beds are ideal for this because they hold moisture well and drain freely.
We planted our leeks into a raised bed that had already been prepared with chicken feather fertilizer. The feather compost fed the soil slowly through the season, and the mulch on top kept the soil cool and moist.
The planting method for leeks is different from most other crops. Instead of digging a hole and dropping the seedling in, we use a dibber or a stick to make a deep hole about 15cm into the soil. The seedling is dropped into the hole, and then the hole is filled with water. The water settles the soil around the roots without the need to backfill by hand.
The seedling can sit quite deep in the hole. As it grows, the soil gradually fills the space, and the stem below the surface turns white. This is what gives leeks their long white shank.
The Leek Bed and Watering
Once the leeks were in the ground, the bed needed to be watered carefully. Leeks do not like to dry out, but they also do not like to sit in waterlogged soil. The balance is to keep the soil consistently moist, without flooding.
This is where our DIY bottle drip system became useful. Instead of standing in the sun with a watering can every morning, we set up bottles above the bed and let them drip slowly through the day. The leeks receive a steady supply of water without the soil ever becoming too wet.
The beds are also covered with grass mulch. The mulch keeps the surface cool, slows evaporation and holds the moisture that drips from the bottles. Between the mulch and the drip system, the leeks have everything they need to keep growing through the heat.
What a Maturing Leek Looks Like
As the leeks mature, the shank thickens and turns from pale green to white. The leaves fan out into a wide, blue-green shape that looks quite different from a young seedling.
The plants also start to push up out of the soil. This is normal, and it is a sign that the leek is approaching its final size. The shank below the surface should be firm and thick when you feel it through the soil.
This is the stage our Raikana leeks are at now. They are still in the bed, still growing, and we are watching them carefully as they move toward their final size.
What to Expect as the Plants Finish Growing
Leeks can be harvested as soon as the shank has thickened enough to be worth eating. Small leeks can be lifted earlier, but they will be thinner and less substantial.
A fully mature leek is usually ready around 100 to 120 days after planting. The shank should be at least 2cm thick, and the leaves should be tall and full. You can harvest them earlier if needed, but the plant will not have reached its full size.
When the time comes, the best way to harvest a leek is to use a garden fork to loosen the soil around it, then gently lift it out of the bed. Pulling a leek straight out of the ground can break the shank, so loosening the soil first is important.
Once lifted, shake off the loose soil and trim the roots. The leaves can be trimmed or left on, depending on how you plan to use the leek. Fresh leeks are best used within a few days, but they can be stored for a week or two in a cool, dry place.
We have not reached this stage with our Raikana crop yet. When we do, I will update this article with what we learned from the harvest.
What I Have Learned From Growing Leeks So Far
Growing leeks has taught me a few things about patience and care. Here are the main lessons from this crop so far:
-
Leeks are slow, but they are patient.
They take a long time to grow, but they wait for you. If you are late to harvest, they will still be there. -
Start with healthy seedlings.
The early stage matters most. If the seedlings are strong and the roots are intact, the plants will grow well. -
Trim the seedlings when planting.
Trimming roots and leaves reduces transplant shock and helps the plant settle in faster. -
Deep planting gives a longer shank.
The deeper the seedling starts, the longer the white shank will become. The hole method works well for this. -
Watering matters more than feeding in the heat.
The drip system kept the leeks alive through weeks of heat. Water, delivered slowly and consistently, was the most important input. -
Do not be in a hurry to harvest.
Leeks hold well in the bed. Leaving them longer gives you a thicker shank and a larger crop.
Gardening Lesson
Leeks reward patience and gentle handling.
Start with healthy seedlings, plant them deep, water them steadily and leave them alone to grow. The reward is a crop that can sit in the garden for months and still give you fresh greens whenever you need them.
Soshanguve, Pretoria, South Africa
Growing Knowledge. Growing Food.