Growing lettuce

Most Queensland lettuce is produced in:

  • Lockyer Valley (autumn, winter, spring)
  • Eastern Darling Downs (spring, summer, autumn)
  • Granite Belt (spring, summer, autumn).

Varieties

The quality and success of a lettuce crop will depend on the varieties you plant, growing methods and location. Carefully consider all aspects of growing and marketing this highly perishable crop before you choose to become a grower.

Lettuce varieties suitable to your growing area are constantly changing. Contact a commercial seedling nursery or seed supplier for the most up-to-date information. Varieties are bred to perform under a distinct temperature range, so make your choice with seasonal and recent weather patterns in mind.

Temperature fluctuations during the growing period have a major impact on performance:

  • a cool-weather variety grown under warm conditions will tend to bolt
  • warm-weather varieties will not produce high quality heads once temperatures exceed their optimal growth range
  • winter varieties will tolerate mild frosts, but no varieties will withstand heavy frosts.

Nutrient level and time of application also impact lettuce quality.

Test different varieties

Test varieties over several seasons, to help develop a variety plan for your farm.

Test new varieties by planting them side-by-side with standard varieties so you can easily compare throughout the growing season. Start with small quantities at first – such as 2 to 3 new varieties every time you plant.

Autumn or spring harvest

In the Lockyer Valley or Darling Downs there's a chance of a light frost in autumn or some hot days in early spring. Be careful to choose a lettuce variety that can handle variations in temperature, since it will often change from day to day during autumn and spring harvest.

Some commercial growers plant 2 varieties, during critical temperature change over periods (e.g. spring into summer) so that at least half of the planting will perform well if the weather is cooler or warmer than usual.

Pests and diseases

Insect pests

  • Thrips
  • Aphids

Diseases

Soil requirements

Lettuce thrives in loose, nutrient rich soils with a pH between 6.0–6.8.

The nitrogen requirements of lettuce depend on the variety, soil type and season:

  • some varieties may not heart up properly with high nitrogen applications
  • the excess nitrogen may endanger groundwater quality, since it can be leached through the soil
  • excess nitrogen application is associated with reduced shelf life as well as with the physiological disorder 'Jelly Butt', which reduces yield and market acceptance.

Irrigation

Plan your irrigation carefully according to lettuce variety and production season:

  • During cool-season production, water every 4–6 days once the crop is established.
  • In warm conditions, you may need to irrigate daily even on clay soils.

Lettuce has a shallow root system and is highly sensitive to water stress and tipburn.

You may need to irrigate frequently:

  • if you're using overhead sprinkler systems on sandy soils (irrigate daily)
  • if you're using drip systems
  • if you're establishing transplants (daily)
  • in hot conditions.

Tensionmeters

A tensiometer measures the tension or suction that a plants' roots must exert to extract water from the soil. This tension is a direct measure of the availability of water to a plant.

Use tensiometers to help you determine irrigation requirements once the crop is established.

  • Place the tip of the shallow tensiometer about 15cm below ground level and another one about 45cm deep. The shallow tensiometer tells you when to irrigate:
    • in cool conditions, irrigate when the gauge is near 25 centibars (kPa)
    • in warm conditions irrigate when the shallow tensiometer reads 15 or 20kPa.
  • The deep tensiometer should normally read between 10 and 15kPa.
  • If it drops to less than 5kPa after irrigation, you should apply less water next time and monitor what is happening using the deep tensiometer.

It is best to have a tensiometer site for each planting. Tensiometers are useful for scheduling irrigations once the crop is established, 10 days to 2 weeks after transplanting.

Hydroponic growing

A hydroponic solution should be easy to make and use fertiliser-grade nutrients.

Nutrient solution recipes are published by researchers and hydroponic societies, and these could be used as the basis of a good hydroponic solution. Published nutrient solutions often have slightly different recipes for summer and winter production so you can change them with the season.

If you're buying a nutrient solution from a store, check that it has a detailed nutrient analysis. If you have growing problems, being aware of the nutrient make-up will help you to find the correct solution.

  • Last reviewed: 14 Feb 2023
  • Last updated: 14 Feb 2023