How to Grow Iceberg
Iceberg lettuce grows in small, dense heads. Commonly used in salads and sandwiches, they are prized more for their texture and crispiness than for the flavor of the leaves themselves. Iceberg was first cultivated in the Salinas Valley of California, then packed in ice and distributed across the US on trains, earning its namesake. Space plants 12" apart with 18" between rows.
7 to 14 days, 40F to 85F
Full Sun, Part Shade
12 " apart
DAYS OF HARVEST
50 to 75
Use row covers to protect very early plantings from cold, to protect young plants from insects, and (supported by hoops) to shade crops when warm weather arrives.
Make succession plantings every week or two, and grow several varieties with different maturity dates for a continuous supply. Moisture, stress, and high temperatures, particularly at night, encourage bolting. As the season progresses, plant more bolt-resistant varieties. Locate plants where they will be partially shaded by taller nearby plants, latticework or other screen.
Lettuce has a shallow root system. Keep soil moist to keep plants growing continuously. Mulch to retain moisture and suppress weeds (unless slugs are a problem). Fertilizing can be helpful to promote faster growth, especially a fish emulsion type that is not high in nitrogen that can cause greens to become bitter. Water lightly but consistently.
For fall crops, time maturity around time of first expected frost. Mature plants aren't as tolerant of freezing as seedlings.
Many varieties of lettuce can be harvested as microgreens, baby greens, leaves, or entire plant. Ideally, greens should be collected early in the day, before the onset of midday sun, to prevent wilting.
Microgreens are usually harvested within 2 weeks after germination by cut entire plant just above the ground, once it is around 3-4" tall.
Baby greens are collected when between approximately 28-35 days after germination, and are collected. Looseleaf, butterhead and romaine types can typically be harvested as baby greens, while iceberg lettuce is not suitable as baby greens.
'Mature leaves' can be harvested from all type of lettuce except for iceberg any time in the growing cycle, until a central stem begins to form. This indicates the plant is preparing to bolt to seed, and greens collected from such plants are often too bitter for consumption.
Entire plants can be harvested in mid-development while the leaves are still plump and tender, but before a stem has started to form. Many varieties of looseleaf lettuce can be harvested numerous times during a single growing season after being cut approximately 1" above the ground.
Some other general guidelines when collecting the entire plant:
Leaf lettuce can be cut as soon as it is large enough to use, usually in 50 to 60 days from planting. Cutting every other plant at the ground will give remaining plants more space for growth.
Romaine and Butterhead lettuce can be harvested in about 60 to 70 days from planting.
Iceberg (crisphead) varieties take longer and should be harvested as soon as a head develops but before outer leaves turn brown. If seed stalks appear, pick the lettuce immediately and store in the refrigerator to prevent bitterness. To store lettuce first wash it well by immersing in water and swishing it around. Place it in a colander and rinse then drip dry. Do this especially if you have used chemicals on your crop. When it is dry place it in a plastic bag in the refrigerator or wrap in paper towels and place in a bowl in the refrigerator. It keeps best at 32 degrees with 96% humidity. Avoid storing lettuce with apples, pears or bananas as they release a natural ripening agent that will cause brown spots and the leaves will decay quickly.
Rubbing separates the plumes and chaff from the seeds. When completely dry, shake the flower stems in the bag. Rub the seed heads between your hands to release more seeds. Put the seed through a fine mesh sieve that allows the seeds through but retains the chaff and plumes; this will give relatively clean seed. Winnowing is difficult because seeds and chaff are about the same size and weight. For extra cleaning use reverse screening, with a smaller mesh that retains the seed but lets small pieces or chaff and plume through. The dust produced during cleaning causes irritation to the lungs and eyes. If cleaning large amounts use a mask and goggles or clean outdoors.
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