Growing Leeks: How to Grow from Seeds and Scraps

Allium ampeloprasum var. porrum, better known as leeks, are cold-weather vegetables that are not only delicious but also nutritious. Best of all, they are versatile and can be incorporated into many dishes, from casseroles to soups. Interested in growing leeks on your own? If that is the case, here we have something for you.

Having fresh, homegrown leeks is always better than buying it from shops. How could it not? You use fresh leeks that you have grown and cultivated yourself. That certainly makes the dishes more delicious! Although leeks are related to onions, leeks are a lot easier to grow. We will show you how to do it. Let’s start with some introductions.

About Leeks

About-Leeks

Leeks are one of those cool-weather crops. Indeed, rather than being hindered by frosts, the taste of leeks improves as it gets one or two frosts. Being a cool-weather crop, the ideal temperature range for growing leeks is between 55 and 75 degrees Fahrenheit. Leeks are biennial albeit a hard freeze can turn them into annual.

There are two parts of a leek. The upper, leafy green part of the plant is known as “flag” while the lower, white part of the plant is known as “stalk” or “stem.” Botanically, these terms are misnomers as the “stalk” is technically a group of leaf sheaths bundled tightly together, just to make it clear.

In general, growing leeks to maturity take between 120 and 150 days. That being said, there are some modern varieties that have a shorter range and can reach maturity faster in just about 90 days. Leeks can be harvested immediately once the base of the plant becomes solid and firm and reaches three inches thick.

Leeks can grow 12 to 30 inches tall and 9 to 12 inches wide. The edible part of the plant is 6 to 10 inches long and 1 to 2 inches in diameter. Leeks’ leaves grow in the opposite direction. At first, a leak plant looks almost flat, but this will change when the leaves grow long enough and become floppy.

Varieties to Plant

Varieties-to-Plant

Like any other vegetables, there are a lot of varieties to select. To get the expected result, it is important to decide which variety before you start growing leeks in the garden. Four of the most common leeks varieties are American Flag, Autumn Giant, Early Giant, and Lancelot. Each one of these varieties has its unique qualities.

1. American Flag

American Flag is a hardy heirloom variety with thick, blue-green leaves. In mild climates, American Flag variety will overwinter. It can reach up to 20 inches in height and 1.5 to 2 inches in thickness.

2. Autumn Giant

As the name suggests, the Autumn Giant really is a giant among leeks. This heirloom variety can grow as tall as 30 inches and as wide as 3 inches when it matures. The downside is that the giant takes longer to reach maturity, between 135 and 150 days.

3. Early Giant

Early Giant is a viable choice for growing leeks in early spring. Compared to the other varieties, this heirloom variety matures much faster, reaching maturation in about 98 days. Early Giant is known for its great flavor and consistent size.

4. Lancelot

A hybrid variety, Lancelot has dark blue-green flags and white shafts, measuring 12 to 14 inches long. This variety is quite adaptable and can grow well in various zones. It has a very short maturation, only about 75 days.

Between these four varieties should you choose? The answer is it depends. It depends on your purpose for growing leeks in the first place. For example, if you want leeks with early harvest, Lancelot variety will suit you. Or, if you look for a hardy variety that can withstand winter, consider American Flag. And so on.

Growing Leeks from Seeds

Growing-Leeks-from-Seeds

You can start growing leeks by either seeding indoors or outdoors. If you want to seed outdoors directly, be sure that the temperature is constantly above 55 degrees Fahrenheit and below 77 degrees Fahrenheit. The ideal temperature for germination is in the 70 to 77 degrees Fahrenheit range.

1. Preparing the seedlings

Here’s how to do indoors seeding:

  1. First, prepare seed trays or pots
  2. Add a rich potting mix into the containers
  3. Scatter leek seeds on top of the mix
  4. After the seeds are scattered, cover them up with soil
  5. The seeds should germinate in 5 to 12 days
  6. Once the seedlings are ready to transplant, remove them from the soil and separate them gently and carefully.

2. Transplanting

The seedlings can be transplanted once they are 6 to 8 inches tall. Before transplanting them outdoor, you need to harden them off so they grow well outdoors. How to harden them off? Just move the seedlings for several hours every day. Increase the duration gradually over time.

Here are the steps to transplant leeks:

  1. Prepare planting beds for your growing leeks.
  2. Create narrow holes for the seedlings, about half the length of the seedlings measured from the top of the stalk to the root.
  3. The planting holes should have a diameter no larger than 1 inch. You can create these holes by poling a dowel into the ground.
  4. Create rows with 1-foot space in between each row. Within these rows, the growing leeks should be planted 6 inches apart.
  5. Plant the seedlings in the holes. You can put the green part of the plant under the soil surface. Don’t worry, it won’t cause any problem.
  6. Water the holes. Don’t backfill them with soil. The wet soil will crumble gradually, filling the holes. This results in loose soil, which enables the leeks to grow to a big diameter.

Growing Leeks from Scraps

Growing-Leeks-from-Scraps

Growing leeks is not the one and only way to grow the tasty green vegetable. That’s right. There is another way to do so: from scraps. To start a new plant from scraps, you will need a leek stalk with a rooted bit at its end.

Here’s how to grow leeks from scraps:

  1. Cut the leek stalk and leave at least an inch of the stalk with intact roots.
  2. Put this stalk bit inside a cup.
  3. Fill the cup with water until half of the stalk is covered. You can also suspend the cut stalk bit with toothpicks in water.
  4. Place the cup somewhere sunny, like a sunny window for example.
  5. Soon enough, you will see green parts emerging from the bit.
  6. You can transplant the bit once it grows to 2 to 3 inches. Or, you can keep the bit and let it grows and harvest.

Growing Leeks: Caring for the Plants

Growing-Leeks-from-Seeds

  • When growing leeks, you need well-drained, rich soil with a pH of 6.0 – 7.0.
  • Mulching the planting bed is a good way to maintain temperature.
  • Leeks need an inch of water per week. So, water accordingly. Avoid over- or under-watering it.
  • Leeks have a high tolerance to cold. They can withstand cold temperatures as low as 5 degrees Fahrenheit. Also, a bit of frost makes the flavor better. That being said, you should pull them out before the ground freezes.
  • Some regions allow you to overwinter leeks. If you live in such a region, keep in mind that the leeks will probably bolt in spring if they have faced frosts during winter and then face gradually warmer weather. Also, if the leeks are in their second year, they will bolt nonetheless as they are biennial.
  • To ensure you have a good yield, pull the leeks before the weather becomes too warm. If you want to save seeds for future use, allow some of the plants to bolt. Bolted leeks that have seeded can still be consumed, but they won’t taste as good.

Harvesting and Storing

Harvesting-and-Storing

After a few months of growing leeks, you will enjoy your reward in the form of harvest. That is, provided that you take care of your leeks well. So, how do you know if the leeks are ready to harvest? When they are fully developed. For most varieties, that means when the stem is at least 1 inch wide.

There are other varieties that don’t grow that big, however. These smaller varieties are already fully developed when they have a diameter of 1/2 to 3/4 of an inch. To make sure, just check the seed packets. You should see the information regarding the mature size of the leeks. A leek with good quality will have a firm, white shaft over 3 inches long.

Here’s how to harvest leeks:

  1. Gently twist and pull them from the ground.
  2. If the soil is dry, you can dig around the plants and lift them.
  3. For easy storage, trim the flags to your desired size.

And here’s how to store the harvested leeks:

  1. Ready an airtight plastic bag.
  2. Put the leeks in the plastic bag.
  3. Place the bag inside a refrigerator, in the crisper drawer. This should keep the leeks fresh for up to a week.

Common Pests and Diseases

Common-Pests-and-Diseases

While growing leeks is not difficult, there are insects and fungi that can damage them cause problems. As such, you need to keep an eye on your leeks, looking for signs of infestation or symptoms of diseases. Prevention is always the best but if you do find your leeks affected by pests and diseases, mitigation can help reduce the damage.

1. Pests

a. Onion maggots

Onion maggots are the small larvae coming from eggs laid by 1/4 gray flies. The larvae tear up the plant using their feeding hooks. What makes things worse is that the damaged plants become more susceptible to other pathogens. Leeks affected by onion maggots have yellow leaves with their stalks rotting.

Crop rotation is a great solution to prevent onion maggot infestation. As for damaged plants, they have to be dug up and destroyed.

b. Leafminers

Leafminers are tiny flies, measuring 1/8 inch with black, yellow, or dark gray colors. When your growing leeks are affected, you will see white winding trails or white blotches on the leaves. These flies lay their eggs inside the leaf, which hatch larvae that feed on the interior of the leaf. To get rid of these pests, use neem oil.

c. Thrips

Thrips are those small, winged insects that damage plants by sucking out their fluids. Affected plants have signs such as black or yellow dots, gray or silver leaves, and twisted and dead leaves. To control these pests, you can use spinose, neem oil, or insecticidal soap.

2. Diseases

Leeks are vulnerable to some types of fungi that cause diseases on the plants. Fortunately, all of these fungi can be controlled with a commercial fungicide. Proper planting techniques, good airflow, regular weed removal, and proper watering practices can help to protect your growing leeks from diseases caused by fungi. Below are some of the most common fungal diseases affecting leeks.

a. Damping off

If your seedlings grow slowly, wilt then die can be a sign of damping off. The tips of the root of affected plants turn black, yellow, or pink.

b. Downy mildew

Gray fuzzy growth on the surface of the leaf can be a sign downy mildew. Other symptoms are pale spots on leaves and in the later stage, the leaves of the affected plants turn yellow and the tips collapse.

c. Rust

A fungal disease that causes orange pustules to develop on the leaves

d. White rot

This fungal disease stunts the growth of leeks, turns the leaves to yellow, and eventually causes the death of the foliage. A fluffy, white growth at the plant base can be a symptom of white rot.

Tips for Growing Leeks

Tips-for-Growing-Leeks

  • Leeks love the sun. So if you want a quality harvest, give them 8 hours of full sun daily.
  • You can trick leeks to grow less green parts and more edible parts by covering up the lower part of the stems.
  • For best growth, side-dress leeks with a balanced fertilizer in the second half of the growing season.

Growing leeks is not difficult. Leeks are not as demanding as onions. All they need are rich, nutritious soil, enough water, and a bit of fertilizer. If you provide your leeks with these, they should grow and yield well. Don’t forget to keep an eye on common pests and diseases so you will get the best yield possible. Happy gardening!

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