After many years of gardening and trying various vegetable varieties, we only started growing leeks recently. However, we quickly fell in love with them because they are not only tasty and attractive but also simple to cultivate (although they take a bit longer to grow). Additionally, leeks are easy to maintain as they are not usually affected by pests, and they can withstand frost.
If you’ve ever wondered what they look like when leeks grow, you’ve come to the right place! In this blog post, we’ll take a look at the fascinating process of leek growth and discover how and why these vegetables are so special. Let’s explore the journey of leeks from soil to plate, from seed to harvestable plant.
What are Leeks?
Leeks belong to the Allium family, which also includes onions, scallions, and garlic. Even though they taste similar to onions, they are much milder and sweeter. Leeks don’t produce bulbs, unlike many other alliums. Their thick, cylindrical white stalks and wide, flat, blue-green leaves, which can be eaten, are their distinguishing features. Leeks are considered a cool-season crop but can grow in various temperatures, similar to onions.
Leeks are very nutritious as they are low in calories but rich in various essential minerals and vitamins, such as manganese, iron, folate, vitamin K, vitamin B6, and vitamin C. Like other plants in the allium family, eat fresh leeks to benefit from the rich flavonoid antioxidants. These antioxidants can offer many health benefits, like being anti-inflammatory, anti-cancer, anti-diabetic, and more. According to WebMD, flavonoids are antioxidants that have several health benefits.
Types of Leeks: Short vs. Long Season
Leek varieties can be grouped into two main categories: those that require a longer growing season and those that require a shorter one.
Short-season leeks, also called “early season” leeks, can be harvested within 50-100 days after planting seedlings. These leeks are usually smaller and have a milder flavor than long-season leeks. Although they are less hardy than long-season leeks, they are perfect for gardeners with short, cool-season growing time. Some of the most popular short-season leek varieties include Rally, Varna, King Richard, and Lancelot.
Long-season leek varieties require over 100 days and up to 180 days for some to mature after transplanting. Additionally, they can be left in the ground for up to 210 days after reaching maturity for storage purposes or until the ground freezes. These larger and more cold-tolerant leeks can be stored longer in the ground or after harvest. Blanching is also beneficial for long-season leeks. Further information on blanching will be provided later.
What Do Leeks Look Like When They Are Growing?
As leeks mature, they form a long, white shaft with a light green leaf at the top. The edible part of the leek is the white shaft, while the leaf is typically discarded. When leeks are young, they look like small, thin onions with long green leaves.
Leek plants are a type of onion related to garlic, chives and shallots. They can grow up to two feet tall with a thick stem at the base that grows out of the ground. The leaves typically have a flat shape but can come in different sizes depending on the variety of leek.
When to Plant Leeks
Do you want to know the ideal time for planting leeks? Typically, gardeners plant short-season leeks during spring to be harvested from summer to early fall. On the other hand, long-season leeks are planted during the early spring in the north and can be harvested until the ground freezes. Leeks that have matured can withstand frost.
Gardeners living in the Southern regions who experience mild winters without frost can plant leeks twice a year – in early spring as well as in late summer or fall, which can be a part of their winter garden. If planted in the fall, these leeks can endure the winter months and be harvested in late winter or spring. People living on the Central Coast of California, which has a moderate climate, can cultivate leeks all year round.
To plant leeks in the spring, start seeds indoors during late winter, around 8 to 10 weeks before your region’s expected last frost date. After the danger of frost has passed and spring has fully arrived, you can transplant the leek seedlings outside. Check out additional suggestions for growing leeks from seed below.
To find the optimal timing for planting leek seeds and transferring them outside your USDA hardiness zone, refer to the Homestead and Chill planting calendars, accessible for every zone.
Growing Leeks from Seed or Seedlings
You can grow leeks in two ways: by starting them from seed on your own or by buying pre-grown seedlings to plant. We have tried both methods but typically prefer starting from seed.
If you want to grow leeks from seed, you need to select varieties that are appealing or well-suited for your climate. In our region, we seek out varieties with natural leek rust resistance – this fungal disease is prevalent in the allium family.
Growing leeks from nursery seedlings is also a good option if you are unable to find the seeds at your local garden center. This method is particularly useful if you don’t have the necessary supplies for starting leek seeds, have a short growing season, or didn’t start seeds early enough.
How to Plant Leeks
When your leek seedlings reach a height of 7 to 8 inches and are as thick as a pencil, it’s time to transplant them outside, whether you grew them from leek seeds or bought seedlings. The following tips for transplanting apply.
Wait until the risk of frost has passed in the spring before transplanting your leek seedlings outside. Watch the weather forecast closely and have a plan in case you need to protect your seedlings from frost. Although mature leeks can handle a light frost (particularly long-season varieties), fragile seedlings are much more vulnerable to damage from frost.
Carefully separate any leek seedlings still growing closely together in the same pot or tray by removing their root ball from the container, loosening the soil, and gently untangling the leeks while being mindful not to harm the shallow root systems or seedlings.
To ensure optimal growth, it is important to space out each leek seedling by 6 inches. This applies whether you are planting them within a garden or in pots.
To plant, you can dig a trench about 6 inches deep or use a dibble or small trowel to create holes between 3 to 6 inches deep in the sandy soil.
When planting leek seedlings, bury most of the stem and leave only a few inches of green tips showing above the soil line. More information about the planting depth can be found below.
Be careful when filling the soil around the seedling stem, and do not apply too much pressure. Alternatively, you can leave the holes and allow them to fill in naturally over time.
How Deep Should I Plant Leek Seedlings?
This topic requires further discussion as there is a lot of conflicting information regarding transplanting leek seedlings. Many gardening experts suggest planting leek seedlings deep (up to 6 inches), burying most of the stem to minimize the need for blanching. This creates a long white stalk that many people prefer. However, deep planting or hilling can also result in more dirt remaining inside the leek, so there are pros and cons.
You don’t need to bury leeks very deeply. Plant them 2-3 inches deep, and they will still grow well, although their stalks may be light green instead of pearly white. If you want them to be extra-white, you can blanch them later after planting. Alternatively, you can let them grow naturally, which is what we usually do.
There are three leek seedlings on the garden soil, lying on their side. Their trays have been removed, and each seedling has a strong root ball with numerous white roots intersecting in the soil clod. Growing leeks can result in a rewarding harvest of allium vegetables.
I can plant the entire root ball of each leek seedling from the 6-packs since there was only one seedling per cell. Some leek seedlings are resting on recently turned garden soil, and a shovel is partially buried in the soil. Consider growing leeks in your garden to diversify your harvests. Before planting these leek seedlings, it’s important to separate them carefully since they have been growing together in a single container.
Leek Growing Requirements: Sun, Soil, Fertilizer, Water & Mulch
For optimal growth of leeks, select a spot with abundant sunshine. Leeks can handle some shade but thrive when planted in areas with full sun.
Leeks can be grown in the ground, in raised garden beds, or in large grow bags. Using well-draining soil rich in organic matter is important for optimal growth. If the soil is heavy or clay-like, you can improve drainage by adding high-quality potting soil and/or horticultural sand.
To ensure that leeks receive enough nutrients, add about two inches of well-aged compost to the soil before planting. Add a sprinkle of slow-release organic fertilizer, gently scratching it into the top layer of soil. If you are growing long-season leeks, you may consider providing them with a mid-season feeding of compost tea, dilute seaweed extract, fish fertilizer, or mild slow-release granular fertilizer. Avoid using strong fertilizers mid-season, as it could cause the leeks to bolt.
To keep your leeks healthy, water them consistently enough to keep the soil damp but not soggy. Once they’re no longer seedlings, add a layer of mulch around the base of the leeks to help retain moisture and regulate temperature. For seedlings buried deep, one to two inches of mulch is enough. Add a deeper layer of mulch for shallowly-planted seedlings or during freezing conditions.
In the garden, numerous onions are growing alongside a small number of leeks in the furthest back row. Adjacent to the onions, peppers are also in the process of growing. In the background is a separate garden bed packed with bok choy, kale, and other greens. Beyond that lies a wall of flowering perennial sage and salvia. It would be a good idea to grow leeks in your garden to enhance their diversity and versatility.
When and How to Harvest Leeks
When harvesting leeks, pick them once they have reached the size you want. Refer to the description of the leek variety you are growing to determine when they are expected to mature and reach the desired size. You can harvest leeks early and eat them when they are still tender, immature versions of their adult counterparts, like onions.
One benefit of growing leeks is that you can harvest them gradually if you choose a long-season variety. These leeks can be kept in the soil until you need them, but make sure they don’t start to flower or get exposed to a hard freeze (although they can tolerate frost). If there’s going to be a hard freeze, either pick the leeks or cover them with mulch and horticultural fleece.
For a successful leek harvest, it’s important to use the right technique. Rather than pulling them, which can lead to damaging the stalk, you should DIG them up. Since leeks have deep roots, insert a small trowel or spading fork into the soil near the stem and lift them out gently from below.
Leek Pests and Diseases
You should be aware of a few common pests and diseases when growing leeks. These include onion thrips, slugs, maggots, and white rot.
Small yellow-brown insects that feed on leaves and onion thrips are more prevalent in hot, dry conditions. To manage them organically, use neem oil spray, introduce beneficial insects, or remove heavily-infested plants.
The larvae of the onion maggot fly these pests feed on allium seedlings, roots, and bulbs. They thrive in cool, damp conditions and can be controlled with beneficial nematodes.
Allium Leaf Miners
Invasive insects from Poland, these pests are currently found in the Northeast and Mid-Atlantic regions of the U.S. They feed on plant sap and lay eggs within plant tissues.
This pest is found in Canada, Asia, Europe, and Africa but has not yet been reported in the continental United States.
Leek Diseases: Fungal Issues
The fungal diseases require management: Allium Rust, Downy Mildew, Pink Rot, White Rot, and Botrytis Leaf Blight. To reduce the spread and damage caused by most fungal diseases, use homemade neem oil spray or dilute potassium bicarbonate spray as effective organic fungicides. For more information on using both solutions, refer to our article on powdery mildew control.
Storing Fresh Leeks
If you don’t plan to use the leeks immediately after harvesting, it’s best to refrain from washing or trimming them. You can remove any dirt from the roots, but avoid cutting into the stalk unless you plan to cook with them in the next few days. Fresh leeks should be stored in a plastic bag or two (for extra-tallness) and kept in the refrigerator. They should remain fresh for up to a week or longer.
If you want to store fresh leeks for a long time, you can keep them in a root cellar with a temperature between 32 and 40°F. First, do not wash the leeks and keep the roots attached. Next, take a bucket of horticulture sand or fresh potting soil and put the leeks in it in an upright position. Cover the stalks with several inches of sand/soil. This method can keep certain varieties of leeks fresh for several months.
Leeks can be preserved in different ways, such as freezing, dehydrating, canning, pickling, or fermenting. We particularly enjoy making leek powder by drying them, resulting in a sweet, onion-like seasoning powder. Instructions on creating and utilizing leek green powder can be found here. This post also includes information on freezing leeks. Another option is freezing potato leek soup, a great way to preserve them.
If you have excess leeks, you can freeze them to save for later. These frozen leeks can still be used in recipes like soups and sauces that require cooked leeks, but their texture may not be as good as fresh, delicious leeks.
For easy use after thawing, slice them into thin rounds and freeze leeks on a parchment-lined tray in a single layer until solid (overnight or 24 hours).
To prevent the leek pieces from freezing together into a clump, transfer them quickly to a freezer-safe container and return them to the freezer for storage. Be careful not to let them defrost while doing so. This will make it easier to remove only the amount needed when using them later on.
Final Words: What Do Leeks Look Like When Growing?
When growing in your garden, Leeks look like long green onions with white stalks and dark green leaves. The leaves are thick and flat, ranging from light green to deep blue-green. When picking leeks from the garden, choose ones with tender white stems without discoloration or wilting. The leaves should be bright and crisp, indicating freshness. As the leeks mature, their diameter grows, and the stems become thicker.
I hope this article has increased your confidence and enthusiasm for growing leeks. With their ease of care, distinctive appearance, and adaptability in the kitchen, leeks have certainly become a regular feature in our garden. If you have any further questions I haven’t answered, please don’t hesitate to ask in the comments below. If you found this article useful, please share it by pinning or sharing this post to spread the love for leeks. Thank you very much for taking the time to read it!