One of the most popular types of lettuce and grown since 1894, the name 'iceberg' comes from when crisphead lettuces were first shipped by train. Ice was piled on the cartons to keep them fresh, giving the appearance of little icebergs. Icebergs have become one of the most popular lettuces in the world; probably because they have become the supermarket staple. There is little comparison, however, between a shop bought Iceberg, and a home grown one. Both retain that beautiful thick crispness of leaf, but it is the flavour of the home grown makes it exceptional. Fresh, crisp and ever so slightly sweet, with leaves that remain crisp for so long, the iceberg is ideal for the pre-prepared salad or as a 'plate' for a starter or main dish. Lettuces are easy to grow in the smallest of gardens or even in pots on a balcony or patio. The iceberg is slow to bolt allowing for longer periods between successional sowing. For the best lettuce experience, pick early in the morning and refrigerate for eating the same day. This gives the maximum amount of flavour, freshness and nutrients.
Prepare the site: Lettuce doesn't do well in very acidic soils, and some say the pH shouldn't be lower than 6.5. A rich soil is excellent for lettuce, but the crop will also do well in average garden soil. The best crops are grown in soil that is deeply enriched with well-rotted manure and is well-fertilized before planting, especially with high nitrogen--leaf-stimulating--fertilizers such as 10-8-4, cottonseed meal, or blood meal.
Timing: Crisphead lettuces are sensitive to heat and need to mature before the first hot spell. Whilst here in Ireland this gives us a very wide window to sow, in more usual climes it is best to sow in early spring. Alternatively, plant in late summer for an early autumn harvest.
Sowing: Sow under protection: February to March (Plant out April) Sow directly outdoors: March to June The perfect temperature for germination is 4 to 16°C (40 to 60°F) rates decline above 20°C (68°F). The perfect temperature for growth is 16 to 18°C (60 to 65°F) Sow at a seed depth of 6 to 12mm (¼ to ½in) Seed will germinate in 7 to 14 days. Sow seeds in short rows about 30cm (12in) apart. To do this, make a shallow trench with a cane about 15mm (¾ in) deep. Space the rows 20cm (8in) apart. Tip a small amount of seed into your hand, take a pinch and spread thinly along the trench. Cover with soil, label and water. If birds are a problem in your garden, spread netting to prevent them eating the seed. When the seedlings are about 2cm (1in) tall, thin them out to give them space to grow, 15 to 20cm (6 to 8in). Make successional sowings at 14 day intervals. On a hot day, water the soil thoroughly before sowing. Try, if possible, to sow during the early afternoon.
Cultivation: A mulch of grass clippings, salt hay, clean straw, or the like, will keep the weeds out and the growing soil moist and cool. Watering is essential if rainfall is scant. The plants need almost constantly moist ground. This is particularly important when the lettuces are one or two weeks away from harvesting, as dry soil now will cause the plants to put their energy into producing flowers.
The key to tender and tasty lettuce is rapid growth, however lettuce has a relatively shallow and compact root system that doesn't absorb nutrients and moisture from the soil very efficiently, which can slow the growth. To encourage fast growth, add plenty of finished compost before planting and again as a side-dressing a week or so after seedlings appear or transplants are planted. Give supplemental feedings of compost tea every few weeks until harvest.
Pests: Aphids – Wash off minor infestations before the plants are eaten. If there is a heavy population grow nasturtiums near the lettuce, or use an organic solution.
Harvesting: Usually ready to harvest after around 70 days . Harvest as soon as the lettuce is large enough to make it worthwhile.. The harvest is over when a central stem starts to form. This is the signal that the plant is getting ready to bolt and the leaves will be bitter.
Rotation considerations: Avoid following radicchio, endive, escarole or artichoke.
Good Companions: All brassicas (except broccoli, but especially radishes), beat, carrot, cucumber, onion family, pole lima bean, strawberry
Bad Companions: None
Nomenclature: This type of Lettuce was grown as far back as 1771, with "Iceberg" being introduced in 1894. The name was only given to this hearting lettuce during the 1920's when they were transported in ice-filled rail cars from Canada, and looked like icebergs among the ice. Iceberg lettuces quickly became popular due to the relative ease of which they could be transported.
|Packet Size||1 gram|
|Average Seed Count||900 Seeds|
|Cultivar||Iceberg. (Heirloom 1894)|
|Common Name||Crisphead Lettuce
|Other Common Names||No|
|Natural Flower Time||No|
|Time to Harvest||70 Days|
|Time to Sow||Under protection February to March or directly outdoors March to May|
|Germination||7 to 14 days at 4 to 16°C (40 to 60°F)|