AHEIA - Providing leadership to support and strengthen Australia's trade in horticultural produce.

Lettuce

Lettuce

History

Originally viewed as a weed, it was only used for its oil rich seeds until the ancient Egyptians later cultivated it for its leaves. The explorer Christopher Columbus introduced lettuce to the Americas in the 15th century and by the late 20th century, the world was consuming lettuce. Lettuce seeds arrived in Australia on the First Fleet and now days, this popular vegetable is often found in backyard gardens around the country.

What are they

Lettuce is a part of the daisy family and is grown as a leafy green vegetable. Lettuce varieties range in sizes, shapes, colours and flavours however crisphead (iceberg), romaine (cos), butterhead and looseleaf are the most popular in Australia.

  • Crisphead has a compact, round head and firmly packed leaves
  • Cos has long, dark green leaves
  • Butterhead has soft green or brown-red leaves
  • looseleaf varieties do not form heads and come in various shapes and colours

How are they grown

Lettuce grows best at relatively cool temperatures and does not like extreme heat or cold. High daytime temperatures greater than 30°C at or near harvest can cause wilting. Lettuce can be grown from seeds or seedlings and requires plenty of water as it has shallow roots.

Where are they grown

Lettuce is grown all over Australia however the main lettuce production regions in Australia are the Lockyer Valley and Eastern Darling Downs (SE Qld); Hay and Central West (NSW); Lindenow and Robinvale (Vic); Manjimup and Gingin (WA); Virginia (SA) and Cambridge, Richmond and Devonport (Tas).

How to know when they are ripe

Lettuce plants are usually ready to harvest in six to 12 weeks. Around a week before your estimated harvest date, pick a few lettuces that appear to be ready to harvest. Push on the top of them to see how firm they are.  If the larger lettuces are firm, cut a few in half and check how closely leaves are packed in the head. If they are packed closely and most of the field has heads of about that size and firmness, the crop is ready to harvest.

Knowing when they are ready for harvest differs between varieties.  This depends on variety, season and the weather conditions

Seasonality

 

Jan

Feb

Mar

Apr

May

June

Jul

Aug

Sept

Oct

Nov

Dec

Lettuce

 

 

 

 

 

 

 

 

 

 

 

 

 

Weather impacts

Heavy winter frosts of -3C will damage lettuce and kill young seedlings. During extensive rainy weather the plants are likely to become infected with diseases.

Local market

Fresh consumption including pre packaged salads.

Storage

Lettuce should be pre-cooled to as close to 1°C as possible within 1 to 2 hours of harvest. After pre-cooling they should be stored at 4°C and 95 to 100% relative humidity.

Nutrition

Depending on the variety, lettuce typically has a good source of Vitamin A, C and K, Iron and folate.

Packaging

Solid lettuce heads are cut, trimmed to 4 to 5 wrapped leaves and packed into waxed cartons, 12 to 16 heads per carton. Lettuce heads should be tightly packed in the carton to avoid movement during transport. Pack in two layers with hearts to the bottom and top, and butts to the middle.

 

 

References

Agriculture Queensland ‘Critical Temperature Thresholds Lettuce’ By Peter Deuter, Neil White, David Putland  http://www.managingclimate.gov.au/wp-content/uploads/2012/02/Critical-temperature-thresholds_Lettuce_V2.pdf (Febrary 2016)  
Queensland Department Agriculture and Fisheries http://era.daf.qld.gov.au/1660/4/3growlet.pdf (January 2016)