Iceberg lettuce has a good number of outer leaves, which help protect the head during transport and handling.
This lettuce type is often sold in banana boxes, and varieties with darker leaves are preferred.
Quality is often determined by the stage of harvesting. As the lettuce becomes older, the appearance may not change, but the eating quality certainly does.
I once watched lettuce harvesting in California. A row of workers walked just in front of the harvester testing the quality of the produce before the packers placed it in boxes.
Each quality tester would place a flat hand on the head of the lettuce, exert slight pressure, then cut the stem. If the head was too hard, it would be left on the ground.
Buyers for supermarkets who require individually wrapped lettuce heads choose varieties where only the head is of good quality; outer leaves are neither desired nor required.
If you plant lettuce for home use, avoid iceberg types, as the entire crop matures at virtually the same time (about 55 days from transplanting). This means you have a very short window to harvest them at the right stage and enjoy them at their best.
As a home grower, rather opt for leaf types, as these can be harvested earlier. Moreover, with so many varieties available, you can harvest individual lettuce leaves for up to two months.
If you would like to experiment with different types, buy a packet of seed mixture, then allow your favourite one or two varieties to go to seed and plant these.
Apart from choosing the correct type for marketing, you need to select the variety that best suits your climatic conditions.
Different cultivars within a category vary in their seasonal adaptability. Some are widely adaptable, while others do well only under certain climatic conditions and in certain temperature regimes.
Disease resistance is another consideration. Humidity and rainfall can induce diseases such as downy mildew and bacterial spot. If you farm under these conditions, select varieties resistant to these diseases.
Some years ago, the Highveld went through an extended phase of early autumn rain.
This resulted in extensive outbreaks of downy mildew and bacterial spot, and many farmers ended up producing unmarketable or low-grade lettuce heads.
The resistant varieties available at the time had slightly smaller heads and a lighter colour. Farmers had to choose to take a chance with the weather and plant a higher-yielding, darker variety, or a lighter-coloured variety with disease resistance in case of unfavourable weather.
If it was rainy, prices would spike and the lighter-coloured, but marketable variety would ensure a very high income.
If it was a dry year, the darker varieties would be in demand, but market prices would be lower.
Bill Kerr is a vegetable specialist and a breeder of a range of vegetables.