Lettuces can be grouped in four botanical varieties, although some other types are distinguished in marketing, according to the sprouting, the type of leaves, the colour, etc. Some of these types are composed by the lettuce " Romana’, " Iceberg", " Trocadero’, " Baby Roman", etc. New varieties are continuously obtained within these types, having better characteristics: resistance to diseases, better sprouting...

Within the species Lactuca sativa, there are four botanical varieties distinguished:

Lactuca sativa var. longifolia, which includes the lettuces that are cultivated for their leaves, although they do not form a real heart. The leaves are usually oval.

Lactuca sativa var. capitata: these are the lettuces forming a tight sprouting of leaves that may show variable shapes.

Lactuca sativa var. Intybacea: these are lettuces of loose and separated leaves.

Lactuca sativa var. augustana, which are lettuces cultivated for their stems, having pointed and lanceolate leaves. They are frequently cultivated in China, and they are know as " asparagus lettuces’.

The two first varieties the most cultivated in the western world.

Lettuces are also grouped in different commercial types according to some agronomic characteristics, like the capacity for sprouting, the consistency of the leaves or the adaptation to a given season. Within the most traditional types we find the ‘Roman’, the "Iceberg" lettuce and the "Trocadero’ type. The most recent types are the "Baby Roman", ‘Little Gem" or baby hearts, "Lollo Rosso’, "Oak leaf’ and "Lollo biondo’.

The "Roman’ lettuce belongs to the longiflora botanical variety; it does not form a real heart. The leaf has an oblong shape and a wide central nerve. This type includes some other types classified according to the shape, colour, bubble, the leaf border and their behaviour:

Valladolid: this type is adapted to winter culture. It bears compact lettuces, 1kg of average weight. They are usually of dark green colour, slightly bubble, with bright leaves and even leaf edge.

Inverna: the lettuces of this type are more voluminous, of a pale green colour, wide, thin and slightly saw-like leaves. Somewhat bubble, the hearts are less tight than those of the type Valladolid.

Parrish Island or Cos: the varieties of this type bear lettuces of intense green colour, with very bubble, thick and crispy leaves.

Romana del Prat: these are narrower, thin lettuces of intense green colour. The edge of the leaf is even. The hearts are badly formed, although they are highly appreciated for their taste and texture.

The group of " Iceberg" lettuces is the one that has undergone a greater growth in the last years. These lettuces belong to the botanical variety capitata and the commercial varieties are distinguished according to colour, bubble and leaves edge. As with the "Roman’ lettuce, this type comprises many others:

Empire: it is adapted to hot climate. It has an average green colour and slightly bubble leaves, of curly edges.

Grandes Lagos: of bright green-coloured leaves, non bubble and with curly edges, it bears medium-size hearts. This type has practically disappeared.

Calmar: they are varieties of bright green leaf, somewhat bubble and with curly edges. It has almost disappeared.

Salinas: it is the most spread type, since the hearts are well-formed and it has a better taste. The leaves are of mate green colour, somewhat bubble and with even edge. The heart is spherical.

Vanguard bears vigorous plants, with dark leaves, bubble and with even edges. They are cultivated in winter.

Another group of lettuce varieties is Trocadero. These belong to the group of lettuces that form a heart (variety capitata). Some varieties of this type are Remco, Dominó and Ventura.

The type Batavia is included within the botanical variety ‘capitata’. It develops a heart of crispy leaves, with a more or less deep saw-like shape. Two varieties of this group are Maravilla de Verano and Dorada de Primavera.

The baby Roman type lettuces have been recently obtained. Their size is uniform and suitable for a familiar salad. They form a heart, they are crispy and they taste good. They measure 20cm, and the weight of the heart ranges between 250 and 450g. Some varieties are Lincoln, Livro, and Doncella.

Another type of lettuces are the baby hearts or Little Gem. They are long-leaf varieties; they form compact hearts of 10-15cm long and 8-10cm of diameter. Some varieties are Ferro, Bambi and Serwood.

Some recent varieties do not form the heart:

Lollo Rosso: these lettuces have red leaves of even texture. Some varieties are Lotto, Valeria and Malibú.

Oak leaf: they are lettuces of red leaf and strong texture, with curled edges. Magalie is one of the varieties of this type.

Lollo biondo: they are lettuces of extremely curled edges, yellowish green colour and even texture. One of the varieties is Cireo.

Due to the commercial importance of this species, there are new varieties obtained as a result of the selection: lettuces with more compact hearts and better formed, adapted to certain climatologic conditions, resistant to diseases, etc.