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

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.

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 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.