Lettuce

Lactuca sativa L.

Order: Asterales

Family: Asteraceae

Names:

Lactuca is from the Latin lac or lactis meaning milk and refers to the milky sap.
Sativa is Latin for sown or planted referring to it as the cultivated form.
Lettuce

Other Names:

Summary:

A salad vegetable widely cultivated for its compact crisp head of leaves.

Description:

Cotyledons:

Two.

Leaves:

Form a compact globular head.
Stipules -
Petiole -
Blade -
Stem leaves -

Stems:

Flower stem -

Flower head:

Flowers:

Ovary -
Calyx -
Perianth -
Sepals -
Petals -
Stamens -
Anthers -

Fruit:

Seeds:

Roots:

Taproot.

Key Characters:

Biology:

Life cycle:

Annual. Seed is sown at any time of year. Heads are harvested 6-12 weeks after planting.

Physiology:

Sensitive to frost. Sensitive to high temperatures. Seed stalks form when temperatures are 20-270C

Reproduction:

By seed.

Flowering times:

Seed Biology and Germination:

Vegetative Propagules:

None.

Hybrids:

Allelopathy:

Population Dynamics and Dispersal:

Spread mainly by intentional planting of seed or seedlings.

Origin and History:

Distribution:

ACT, NSW, NT, QLD, SA, TAS, VIC, WA.
Not naturalised.

Habitats:

Climate:

Cool temperate. Prefers temperatures between 10 and 200C. Cool nights required for good quality. High temperatures lead to bitterness.

Soil:

Well drained with a pH of 6-6.5.

Plant Associations:

Significance:

Beneficial:

Detrimental:

Toxicity:

Not recorded as toxic.

Legislation:

None.

Management and Control:

Thresholds:

Eradication strategies:

Herbicide resistance:

Biological Control:

Sensitive to Necrotic Yellows virus which is spread by aphids from Sowthistle to the crop. Lettuce is also affected by a seed borne mosaic virus.
Important diseases include Downy Mildew, Grey Mould Rot, Sclerotinia Rot and anthracnose.
Pests include Aphids, Light Brown Apple Moth and Rutherglen Bug.

Related plants:

Prickly Lettuce (Lactuca serriola) is probably the wild parent of Lettuce.
Wild Lettuce (Lactuca saligna) has narrower lobes and no spines on the stem leaves.

Plants of similar appearance:

References:

Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne).

Reid, R.L. (1990) The Manual of Australian Agriculture. (Butterworths, Sydney). P145, 341.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.