If you are wondering how to grow leeks in your home garden using only organic techniques, this is the right article for you. Leek, scientific name Allium porrum, is an herbaceous crop belonging to the Liliaceae family. It shares similar characteristics with onion and, like onions, is a healthy and tasty vegetable. It is highly appreciated in the kitchen for its unique flavor and is consumed in various seasons of the year. In this article, we will explore the peculiarities of leek cultivation, different varieties, the ideal seasons for cultivation in the open field, and the necessary cultivation techniques to improve its quality.
But let’s start with the plant’s characteristics.
The Leek Plant
Like onion and garlic, leeks have a long history and were widely cultivated in ancient civilizations such as the Egyptian and Roman cultures.
Leeks are a biennial crop but are cultivated annually in the vegetable garden. In the first year, the characteristic fleshy stems are formed. In the following year, if the leeks are not harvested and left to grow, they produce flower stems. These flowers bloom at the beginning of summer and produce shiny black seeds.
The plant has a fasciculated root system with numerous dense roots that extend up to 50 cm deep.
The leaves are light green, flat, and broad. They are arranged in a fan shape in two opposite series, forming an enlarged and whitish stem with their sheaths at the bottom.
The stem is also known as a false bulb. It is elongated and cylindrical, measuring between 20 and 40 cm in length and 2 to 4 cm in diameter, depending on the variety.
This fleshy stem is the edible part of the vegetable. When fully developed, especially if properly blanched, it has a pleasant and delicate flavor, similar to onion but sweeter.
If you decide to grow leeks in your home garden, there are several varieties to choose from, mainly distinguished by the size and texture of the stem. Let’s see the most common ones:
- Grosso corto d’estate: early cycle with rapid development
- Mostruoso di Carantan: short and thick stem, tender and tasty
- Gigante d’inverno: very vigorous with a thick stem
- Invernale di Parigi: typically long and white stem
- Zampa di elefante: with a very thick and perfectly white stem.
How to Grow Leeks
Growing leeks is relatively simple, especially considering their ability to adapt to various climatic conditions. Depending on the variety and chosen cultivation cycle, leeks thrive well in both warm-temperate and cool-temperate climates.
Choosing the Period: Direct Sowing or Transplanting?
When deciding to grow leeks, it’s essential to understand the timing for direct sowing or transplanting the seedlings.
Leek seeds have a relatively long germination time. It takes about two months from seeding in seedbeds to the formation of a young plant ready for transplanting. This will also influence the harvest time, which can be in summer, autumn, or winter.
For a summer harvest, sow the seeds in a heated seedbed in December-January and transplant to the garden in March-April.
For an autumn harvest, sow the seeds in a seedbed at the beginning of spring.
Lastly, for a winter harvest, sow the seeds in May-June.
Thus, the sowing can be staggered from December to June.
The long waiting period often leads gardeners to purchase pre-formed seedlings from a nursery. Generally, leek seedlings are chosen to be around 20-25 cm in length for direct transplanting.
Soil and Fertilization
The most suitable soil for growing leeks is a medium-textured soil that is sufficiently fresh and well-draining. Fertilization can be done a month before the planned transplanting, adding well-matured manure to the soil. Avoid using fresh manure. Alternatively, before transplanting, you can use the result of home composting.
Transplanting Distances and Irrigation
Growing leeks requires close distances. There should be 15-20 cm between plants in the row and 30-40 cm between rows.
Irrigation, preferably done with a drip irrigation system, is necessary, especially for leeks grown in the spring and summer. However, the water requirements significantly decrease during the autumn and winter months.
Growing leeks requires a medium-long cycle during which specific cultural care is necessary.
For example, at a certain point, it will be necessary to perform weeding to eliminate weeds. This is followed by the first earthing-up, an operation needed for blanching the stem. Another earthing-up should be done about a month before the expected harvest. Earthed-up soil, as seen in the cultivation of another important crop, fennel, prevents subsequent weed growth and facilitates stem enlargement, turning it white, tender, and tasty (blanching).
Harvest and Uses
Leek harvesting occurs gradually, with plants being uprooted as needed. Leeks can be consumed raw, boiled, and dressed with extra virgin olive oil, chili, and salt.
These are the simplest ways to use them. Naturally, there are many delicious recipes with leeks, and you can also create your own with a little imagination.
Biological Pest Control
Unfortunately, when growing leeks, you should be aware that some pests may threaten your plants. The most dreaded is undoubtedly the leek stem and bulb nematode (Ditylenchus dipsaci), which we have discussed in the past. If you find this pest, it’s essential to perform a brassicaceous cover crop before proceeding with any new cultivation.
Other harmful animal pests for our leek crop include the leek moth (Acrolepia assectella) and the onion fly (Hylemia antiqua). For these insects, you can intervene with biological treatments based on Bacillus thuringiensis when they are in their larval stages.
Regarding fungal diseases, it is essential to control powdery mildew and leek downy mildew (Phytophthora porri). Treatments based on nettle macerate and sodium bicarbonate can be used. In advanced stages of the disease, cutting the plant at the base can be an option. The plant has the ability to regenerate, although this will require some time.
- University of Wisconsin – Madison – Leeks – This article provides a comprehensive overview of leeks, including their history, cultivation, varieties, and culinary uses, describing them as a mild onion-like vegetable.
- University of Nebraska-Lincoln Extension in Lancaster County – Leeks: “The Gourmet’s Onion” – This article describes leeks as a cool-season crop with a mild onion-like taste, providing guidance on growing, blanching, and cooking methods.
- Encyclopaedia Britannica – Leek | Culinary Uses, Growing Tips & Nutrition – The leek, a hardy biennial plant, is native to the eastern Mediterranean and the Middle East, known for its mild, sweet, onion-like flavor.
- Cancer Prevention Research – Garlic and onions: their cancer prevention properties – The Allium genus, including garlic, onions, shallots, leeks, and chives, is known for potential medicinal properties, particularly focusing on cancer prevention.
- Ecotoxicology and Environmental Safety – Residue dynamics of procymidone in leeks and soil in greenhouses by smoke generator application – This study analyzes procymidone residue in leeks and soil, exploring procymidone residue dynamics and residues in supervised field trials in greenhouses.
- Food Chemistry – Bioaccessibility and bioavailability of selenium species in Se-enriched leeks (Allium Porrum) cultivated by hydroponically – This research investigates selenium in Se-enriched leeks cultivated hydroponically, revealing that approximately 90% of total selenium was transformed into organo-selenium species.
- Journal of Agricultural and Food Chemistry – Influence of processing on total, monoglutamate and polyglutamate folate contents of leeks, cauliflower, and green beans – This study explores the bioavailability of dietary folate in leeks, investigating the influence of processing treatments on folate content.