Mar 5

Spotlight Edible of the Day: Cool Season Crops – Leeks

“I would desire you to eat it…if you can mock a leek, you can eat a leek”

William Shakespeare (1564-1616) King Henry V

A beautiful and ancient monocot, the leek is, as far as I’m concerned, a necessity in any serious cool season culinary garden. Certainly, there is hardly a European garden without the gorgeous blue-green stand of leeks in winter. In the U.S., however, the leek remains under-appreciated.

 

From the edible landscaper’s perspective, the leek provides a productive upright, structural element that broadens our design palette with its coloration (white to blue-green to dark green and even purple). From a chef’s perspective, leeks are an integral ingredient in a production garden that provides an elegant, mild, delicate flavoring to sauces, salads, soups, and a myriad of other dishes.

Genus: Allium. Alliums (garlic, leek, onion, scallion & shallot) are a genus of plants that have provided flavorful seasoning in food for thousands of years.  Onions and garlic were two of the most important crops consumed in ancient Egypt.  Islamic legend has it that when Satan left the Garden of Eden after the fall of man, garlic sprang up where his left foot stepped, and onions grew where his right foot was placed.

Family: Alliaceae  (subfamily Allioideae of Amaryllidaceae)

Species: Allium ampeloprasum (porrum) – which includes leeks, elephant garlic

A bit of botantical history –

The leek is a biennial onion relative that is grown as an annual for its long, thick stem, the white to pale green part of which is used as a staple in the home and professional kitchen. The modern leek is related to the wild leek of the Mediterranean and the Canary Islands, Madeira, and the Azores. While leeks have long been a staple winter vegetable of Northern Europe, they are decidedly unsung and underappreciated in the U.S.  Let’s change that!

Medicinal qualities –

All of the foods in the Allium family are full of antioxidants and phytonutrients. Organic sulfuric compounds give these plants their unique piquant flavors and make them highly regenerative; the more pungent the flavor, the more powerful the health benefits. Garlic and scallions, along with onions, leeks, chives and shallots, are rich in flavonols (substances in plants that have been shown to have anti-tumor effects). New research from China confirms that eating vegetables from the allium group can reduce the risk of prostate cancer.  Throughout the history of medicine, leeks have been known to clean your arteries and retard the growth of viruses, yeasts, ferments and other pathogenic organisms. They are also full of manganese, Vitamin C, and B6. They do not have the same antibacterial properties of garlic, but they do have similar cancer fighting benefits and they stabilize blood sugar much like onions. Leeks are also high in iron and folate. See the GroEdibles blog “The Pharmacy in Your Garden – The Hidden Medicinal History of Your Favorite Plants”.

Varieties:

I love leeks. These three key words from UCCE, Stanislaus County sums them up perfectly:

• Stalwart—Cold tolerant, overwintering through the snows of winter unharmed.
• Long—Tall; some winter varieties achieve the same dimensions as a baseball bat. In fact, leeks, unlike most vegetables, achieve full flavor and ideal texture as they size up. A full-size, mature leek eclipses a young baby leek in both categories.
• Slow and steady—While many books and catalogs I have seen indicate 4–8 weeks from seeding to transplant and 50–100 days from transplanting to maturity, 10–12 weeks from seed to transplant and 90–120, or even 180 days from transplanting to harvest is the norm in my experience.

There are two basic types of leeks: summer types (long shanked—bulbless) and winter types (short shanked—slight bulbing).

Summer varieties

Summer varieties feature taller plants with light- to mid-green foliage, almost to the point of appearing nitrogen deficient. The shanks are long (8–12 inches) and self-blanching. They are “quicker” to maturation (90–100 days; all dates are from transplants) than winter types and have a lighter, slightly milder taste. Summer types are more heat tolerant and less cold hardy than winter varieties. They are generally grown spring to fall, although in mild winter areas (like parts of So. Cal.) they are overwintered.

Kilma  (90 days) – Fast-growing summer leek with 10–12-inch shanks. Only tolerates slight frosts.

King Richard and Titan (90-100 days from transplant) – Virtually indistinguishable from one another. One of the earliest-maturing varieties. Long (10–12 inch) self-blanching shanks. Light green foliage. Light, sweet texture and taste. More heat tolerant than any other variety. Some cold tolerance (35˚–32˚F), but not truly winter hardy. Will deteriorate quickly with extensive winter rains.

Lincoln – Often used for baby leeks or bunching, leaves similar to King Richard.

Blue Solaize (100-120 days from transplant) – This is a beautiful French heirloom, truly blue-colored leaves that turn violet after a cold spell. Very large, 15-20″ stalks, sweet medium-long shaft, extremely hardy. Good for short-season areas and winter harvest.

Winter varieties

Winter varieties possess dark, almost blue-green foliage with shorter, squat plants. They are slower to mature (120 –180 days) and the shanks are fatter, growing 3–4 inches across, often with some basal bulbing. Even with hilling there is less blanched, succulent edible portion of the stem. They offer a richer, meatier taste and texture. Winter types feature minimal heat tolerance and excellent cold tolerance for gardeners dealing with temperatures consistently in the teens.

American Flag (130 days) — Pure white blanched stems with mild sweet flavor and good winter hardiness.

Blue De Solaise (105 days) – Old French variety with bluegreen to almost blue foliage tinged with red. Extremely cold hardy with fat, succulent shanks.

Broad London (120 days) – Very squat, short (4–6 inch) shanked, sweet, creamy-textured old variety. Some heat tolerance and moderate cold tolerance.

Giant Musselburg – Old German variety, 150 days to maturation, pure white, sweet, tender, short shank, dark green foliage.

Unfortunately, with rare exceptions, U.S. seed catalogs usually offer only one to three varieties of leeks.  Northern European seed companies usually feature greater varietal diversity, types and varieties. Here are some U.S. seed companies that seem to carry the rarer leek varieties: Irish Eyes, Heirloom Seeds, Sustainable Seed Co., Cherry Gal, Seed Savers

Until the 1990s all leeks were open pollinated (OP) varieties, not proprietary F1 hybrids with corporate ownership. New methods have made hybridizing them possible, so now many seed catalogs offer both.

A word about open pollinated (OP)  v. hybrid: It is, of course, a personal choice but HGEL urges its clients to use open pollinated or heirloom seeds whenever possible. There are many instances when a hybrid choice is preferred (increased vigor or disease resistance for a challenging garden site or beginner gardener). I have my own hybrid favorites but my choice is to use open pollinated (OP) as often as I can.

Open pollinated seeds are pollinated by wind or bees and their traits are somewhat fixed within an exceptable range of variability. Heirloom seeds have been passed down for many years and have been preserved and kept true. The heirloom usually yields a superior product regarding taste, color, flavor and texture; all qualities that are of paramount importance to a commercial or home edible garden grower. As long as there is no cross pollination, you can harvest the seeds for next year and expect to get similar results. Hybrids result from a deliberate cross between two inbred lines. They are becoming increasingly popular because they usually are more disease resistant and vigorous than open-pollinated varieties.  Seed saved from hybrids produces many different plant types and are not true to the parent plant which may be a disappointment for gardener who has unknowingly saved and planted hybrid seed. Seeds saved from hybrids usually do not produce the desired results.  

To be sure, check the package to see if it says “F1 hybrid.” F2 plants are not hybrids and lend themselves to seed saving.  Most importantly, however, using open pollinated or heirloom seeds will insure the continuation of our seed source, increase sustainability and support our smaller seed companies.

Climatic Requirements:

Along with kale, leeks are the most cold-tolerant of vegetables. If established in late summer they can overwinter through the frozen ground and snow pack. In fact, the colder the temperature, the sweeter the taste. On the other end of the spectrum, they will survive, but are not at all fond of temperatures consistently above 85˚F.

Soil Requirements:

All alliums are shallow-rooted crops that tolerate a wide variety of soil textures, however, dense clay soil or rocks can hinder growth and development.  Prepare most garden beds with at least 2 inches of compost mixed into the soil to create ideal conditions for alliums. A soil pH of 6.0 to 7.0 is optimum.

Cultural Practices:

Blanching

Hill or mound soil up around the lower parts of the stem (shank) to “blanch” or make white that portion of the shank. This produces a larger, more succulent useable area of the plant. Do this several times during the season as the plant grows taller. Doing it heavily just once tends to rot the shank.

Irrigation

When watering alliums, keep garden soil moist, but not soggy.  Allow it to dry out somewhat between watering.  Avoid wetting the plant when applying water in order to avoid disease and pests. If possible, irrigate with drip lines, or soaker hoses. If using overhead (sprinkler) irrigation, do it in the morning so the plants dry quickly as the day warms.

Weed control

Weed control is important. None of the alliums like competition, so remove any weeds growing in your garden bed.  Weed carefully between the bulbs, as they are easily bruised.   Because leeks are shallow-rooted, hand pulling is recommended in lieu of using tools. Cultivate lightly to avoid root damage. Applying organic material as mulch can provide a temporary weed barrier adding nutrients to the soil as it degrades.

Planting Requirements and Propagation

Leeks are better as transplants versus direct sowing. A transplantable seedling (10–12 weeks old, 1/4-inch stem diameter) can be raised in intensively broadcast sown flats or nursery beds. Because they are monocots with a vigorous fibrous root system and a narrow, waxy leaf surface, leek transplants can be barerooted with minimal transplant shock.  Grow leeks, which can take up to five months to mature, like long-season onions.

Growing alliums from seed takes patience and persistence (c’mon – we’ve got plenty of that…we’re gardeners after all!).  Germination can be a difficult proposition as seedlings grow slowly and are very sensitive to competitive weeds.  Plant seeds in containers and transplant seedlings into your garden, or plant seeds directly into your garden bed. Sow seeds 1/2” deep, 1/2” apart in rows 1 1/2 to 2 feet apart.  Seeds are tiny, so if you can’t space them apart, sprinkle them along the row and then thin later (if you’re like me, you do NOT like to thin!).  The size you choose to harvest your leeks will determine your spacing: more space in between plants that your intend to grow to a 3-4″ diameter. In my small space gardens and combined with the fact that most of my chefs prefer their leeks at the 1-2″ diameter size, I can get away with planting mine closer together.

Fertilization

Alliums grown in compost enriched soil will not need additional fertilizer. If you wish to fertilize, use a liquid kelp or balanced fertilizer 3 weeks after planting.  Stop fertilizing 6-7 weeks before harvest.



Cornell University Cooperative Extension, "Fertilizing Garden Soil"

I stress that just by adding organic matter such as well-rotted manure or compost to the soil before planting and seasonally you will increase the level of nutrients, improve soil microbial activity, and increase water-holding and nutrient-holding capacity. Organic matter also improves the physical condition or texture of the soil for cultivation and improves soil structure so the surface of the soil does not crust. Any soil can be/should be improved through the addition of organic matter. As HGEL advises, cover crops are also an important, inexpensive way to add organic matter to the soil, and much of plants nitrogen needs can be met via cover cropping.  Before applying amendment or fertilizer it is always a good idea to do a soil test so that you know exactly what is in or isn’t in your soil. Contact your local County Extension office for information on soil testing. Fertilizer may be either broadcast and worked into the soil before planting time or side dressed two inches to the side and three inches below the seed at the time of planting.

The Quick and Easy Guide to Organic Fertilizers – Cornell University Cooperative Extension

How to convert an Inorganic Fertilizer Recommendation to an Organic (Univ. of Georgia)

Pest/Disease Control:

Pests & Disease

Leeks are virtually bulletproof when it comes to pest and disease problems.

Follow this link for some things to watch for: http://www.ipm.ucdavis.edu/PMG/GARDEN/VEGES/onions.html

In an organic system pest and disease management is based on prevention. The goal is to have a healthy, balanced plant and soil system in which pest populations will stay within tolerable limits. In a conventional system, synthetic pesticides may help a grower save the current crop from an immediate pest problem; however, in many cases, the problem recurs or another develops AND the cumulative effect of using synthetic fertilizers or pesticides is damaging to the environment, humans and animals. The organic approach is based on the theory that major pest problems usually occur when something is out of balance in the system. These are questions organic gardeners should ask themselves when things seem to be going wrong:

-Are the plants undernourished or stressed from growing too quickly?

-Is there a nutrient imbalance?

-Is the soil too wet or too dry?

-Has a good crop rotation been followed?

-Is there a diversity of plants to support beneficial insects?

Studying the problem and trying to determine why it occurred should help prevent similar problems in the future. This will, of course, take time to learn and develop. Unless gardeners refuse to use any pesticides, they may at times choose to apply some organic pesticides to save a specific crop.

A Word about the Integrated Pest Management (IPM) approach

This is system is well-suited for organic production and one, as a Master Gardener, I always recommend. IPM is a system in which insects, diseases, and weeds are closely monitored, and different methods are used to keep pest populations at levels that are not economically damaging with minimal adverse environmental effects. IPM encompasses use of cultural and biological control methods, use of resistant varieties, and a VERY judicious use of pesticides. HGEL recommends that, in the event pesticides must be used, select ORGANIC ones with low toxicity, non-persistent residues, narrow spectrum of control, and low environmental impact.

A Resource Guide for Organic Pest and Disease Management (Cornell Univ.)

http://www.nysaes.cornell.edu/pp/resourceguide/index.php

There are four regional IPM centers in the U.S. – North Central, Northeastern, Southern and Western.

Here is a link to a searchable database to find the IPM sites in your region:

http://www.ipmcenters.org/

There is no guarantee that once an organic system is established there will never be a disease, weed, or insect problem. Stressful conditions that a gardener cannot control will occur, such as weeks of endless rains, droughts, periods of extremely high temperatures, hurricanes, plagues of grasshoppers, or hail. Likewise, if an airborne disease invades your area, your plants will probably be infected. However, with careful observation and preparation, an organic system should progressively have fewer pest problems as years go by.

Harvest/Storage:

Harvest

Leeks are ready for harvest when the bulb is 1” in diameter.  Don’t look for the flags (leek leaves) to turn brown as other alliums do…they stay green. Harvesting is all about size. Most of my chefs prefer to use them on the smaller size. Certainly, in my smaller gardens, harvesting them at a smaller size makes perfect sense. Use a spading fork to loosen the ground around the leeks, then gently pull them from the garden.  Leeks will last longer if left in the ground until ready for use.

Storage

Once harvested, they can be stored in the refrigerator for several weeks.

Favorite Recipes

Fine Cooking

AllRecipes.com

101Cookbooks.com

Epicurious.com

How to Clean Leeks

Posted by GeriMiller. Filed under Cool Season Crops, Garden Care, How To Guides, Spotlight. Tags: cool season edibles, edible, edible gardening, edible landscaping, gardening, gardening guides, harvesting, homegrown vegetables, how-to guides, urban farming, vegetable gardenings