There are two main colors of lettuce: green and red. There are many combinations of both.
There are four popular types of lettuce grown in the United States: romaine, butterhead, head and loose-leaf lettuce. Although the growing and care process is similar for all types, each lettuce has distinct characteristics in the garden.
Lettuce is hardy and can be planted as early as the soil can be worked. It is a cool weather crop and grows best at temperatures of 60–65°F. Careful variety selection is important for hot weather plantings. Sow every 3 weeks for a continuous supply of fresh lettuce.
Lettuce seed can enter thermal dormancy when exposed to high temperatures. Optimum germination results at soil temperatures of 60-68°F. The priming process in pelleted lettuce seeds broadens the temperature range in which the seeds will germinate, overcoming some of their thermal dormancy.
I suggest that you start 2 to 3 seeds in a three or four inch CowPot.
These are made from cow manure and will decompose in about a year or less.
The advantage is CowPots can be directly planted in the soil which does not disturb their roots. But they do dry out faster than black pots and will need to be watered every couple of days.
It is important that the pots be kept below 75 degrees while in the germinating stage.
Before planting outside, harden seedlings off. Harden seedlings by reducing water and temperature for 2-3 days before planting outdoors. Properly hardened transplants can survive temperatures as low as 20°F.
Transplant iceberg and romaine lettuce 10-12" apart, in rows 18" apart. Other types 8-10" apart in rows 12-18" apart for full-size heads or 6" apart for mini heads.
When direct sowing keep in mind that seeds will germinate even at low, 40 degrees, soil temperature, but poorly above 75 degrees depending on the variety and seed lot.
Sow seeds 6 seeds per foot, rows 12-18" apart. Cover seed lightly, about 1/8", and firm soil gently.
Thin iceberg and romaine lettuce to one plant every 10-12", other types 8-10" for full-size heads or 6" for mini heads. Dry soil must be watered to ensure coolness and moisture, and for uniform germination.
A variety's description followed by MT0-30 indicates that the seed offered for sale has been tested for the presence of Lettuce Mosaic Virus and that no LMV was found in a sample of at least 30,000 seeds.
Leaf types can have leaves picked and will continue to grow. On head types, like iceberg, harvest the whole head. It will not grow back.
Aphids can easily destroy a lettuce patch. Leaves curl and wilt as nutrients and water are sucked away. Aphids also spread disease and create mold issues. You’ll find these annoying little white pests hiding on the undersides of lettuce leaves. There isn’t a systemic insecticide to control aphids, so your best option is to encourage natural predators, such as lady beetles, or to apply a horticultural soap or neem oil.
Snails, slugs and caterpillars also love lettuce. Insecticides are one option, but traps, organic bait and hand picking provide organic solutions to these common pests.
If you notice your lettuce beginning to brown and curl, it could be suffering from a physiological condition known as tipburn. Tipburn is often seen on lettuce when moisture is not consistent. Simply trim the browned lettuce and begin a consistent watering schedule.
There are many good videos on YouTube that talk about growing lettuce.