Lettuce 'Great Lakes'

Lettuce 'Great Lakes' was first introduced in 1941 by the United States Department of Agriculture and the Michigan Agriculture Experiment Station, and was the first modern Iceberg variety to be introduced.
Noted to have a denser head than any European crisphead lettuces bred prior to it, 'Great Lakes' is heat and cold tolerant and has a strong resistance to bolting and tip burn. It produces large, glistening, well-rounded heads, well-folded and fine-flavoured leaves with a crisp texture.

Created by Thomas W. Whitaker, a world renowned authority on lettuce, and named Great Lakes, although it was actually bred in California. In 1944 it was the All America selections winner.
Because of its ability to produce marketable heads under adverse climate conditions Great Lakes became one of the most widely planted varieties. At one stage 95% of commercial production and consumption was of this type and it dominated lettuce production until 1975. It has been the farming standard for commercial growers for over 60 years and was the market leader until pre-packaging of loose leaves took over.

Nothing can beat this variety as a consistent producer of good-sized, crisp, round heads. ‘Great Lakes’ can be sown all year round in temperate regions, during March to September in subtropical areas or from September to February in cold regions. It holds well in warm weather, enduring summer heat without running to seed. From sowing till harvest takes 12 to 13 weeks to full maturity.
Easy to pick and prepare. ‘Great Lakes’ produces large, crinkled leaves which form a dense head in the centre. It is an excellent variety for salads, for shredding and adding to wraps, burgers and sandwiches and has very good storage ability if kept refrigerated.

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 generally sensitive to heat and need to mature before the first hot spell. However, Lettuce ‘Great Lakes’ can be sown all year round in temperate regions, during March to September in subtropical areas or from September to February in cold regions.

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.

Origin:
Wild lettuce, from which modern lettuce is derived, originated in Asia Minor. The ancient historian Herodotus records its presence on the tables of 6th century Persian kings, and throughout the following centuries it became a popular crop all over Europe. Columbus took it with him to the New World, starting its spread over the North American continent. Without a doubt, lettuce now holds a place in nearly every garden on the globe.

Nomenclature:
This type of Lettuce was grown as far back as 1771. Iceberg Lettuce was developed by W. Atlee Burpee at his farm, Fordhook Farm, at Doyleston, Pennsylvania. It was released commercially by Burpee seeds 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.
The 'Great Lakes' variety of Iceberg lettuce emerged in the 1940s, from a cross between Brittle Ice lettuce (a sister lettuce also developed by Burpee) and another crisphead lettuce.

The Great Lakes (also called the Laurentian Great Lakes or the Great Lakes of North America) are a series of interconnected freshwater lakes located in northeastern North America, on the Canada–United States border, which connect to the Atlantic Ocean through the Saint Lawrence River.
Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on earth.