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• Lactuca sativa

Lactuca sativa — cultivated lettuce

Facts

Cultivated lettuce (Lactuca sativa) has been around for thousands of years, but is apparently derived from prickly lettuce (Lactuca serriola), native to Eurasia and itself a common weed in North America. As a naturalized weed, cultivated lettuce is typically ephemeral, but it is found throughout most of the world. Lettuce is unquestionably the leafy vegetable most eaten by humans, and hundreds of cultivars exist.

Habitat

Anthropogenic (man-made or disturbed habitats), meadows and fields

Characteristics

• Flowers

  Bract color

  the bracts are not colored or tinged with pink, red or purple

  Bract cycle number

  there are two main cycles of bracts

  Bract inner side hairs

  the bracts are not hairy on their inner surfaces

  Bract outer side hair type

  the bracts are not hairy on their outer surface

  Bract outer side hairs

  the bracts are not hairy on their outer surfaces

  Bract shape

  • the main bracts are lanceolate (widest above the base, then taper narrowly towards the tip)
  • the main bracts are linear (long and very narrow)
  • the main bracts are of a different shape than the given options

  Bract spines

  the bracts have no spines

  Bract tip orientation

  • the bracts are pressed against the plant, or spreading out at the tips
  • the tips of the bracts curve outwards and downwards from the plant

  Bract tip shape

  • the tips of the bracts acute (have a sharp point)
  • the tips of the bracts are obtuse (have a blunt point)

  Bracts

  the bracts in separate cycles are similar or gradually changing from the outer to inner cycles

  Disk flower color

  NA

  Disk flower lobe number

  NA

  Disk flower number

  NA

  Disk flower proportions

  NA

  Disk flower reproductive parts

  NA

  Disk flower shape

  NA

  Flower head number

  each flowering stem has four or more flower heads on it

  Flower head outer flowers

  at the outer edge of the flower head, each flower has a single enlarged lobe or strap

  Flower head platform

  the base has no bristles or papery scales

  Flower head position

  some or all the flower heads are grouped in clusters of two or more

  Flower head profile

  • the disk is flat or nearly flat across the top
  • the disk is rounded across the top

  Flower head shape

  the sides of the flower head are roughly parallel, like a cylinder

  Flower type in flower heads

  the flower head has ray flowers only, meaning all of the individual flowers of the flower head have a strap-shaped ray, which may or may not have teeth at the very tip of the ray

  Height of flower head base

  6–15 mm

  Inflorescence branching (Solidago)

  NA

  Inflorescence shape

  • the inflorescence is flat-topped in profile
  • the inflorescence is not flat-topped but appears rounded, with some flower heads distinctly higher than others

  Number of bracts at flower head base

  5–13

  Ovary beak

  there is a beak on the ovary

  Ovary cross-section

  the ovary is compressed (flattened)

  Ovary hair type

  the ovary has no hairs on it

  Ovary hairs

  the ovary has no hairs on it

  Ovary lines or ribs

  • there are four to six lines or ribs visible on the ovary
  • there are seven to nine ribs visible on the ovary

  Ovary profile

  in profile, the ovary is roughly egg-shaped, but widest above the middle

  Ovary surface

  the ovary surface is textured with tiny points, bumps or wrinkles

  Ray flower color

  • blue to purple
  • yellow

  Ray flower reproductive parts

  the ray flowers have both carpels and stamens

  Ray flowers

  • 11-15
  • 16-25
  • 26-50
  • more than 50

  Reproductive system

  all the flowers on the plant contain both carpels and stamens

  Rim at top of ovary

  the central flowers have a disk-shaped platform above the ovary

  Smaller bracts at base of bracts

  there is no smaller, outer cycle of bracts

  Style branch number

  NA

  Swelling at base of flower head

  the peduncles are not swollen, or only slightly

  Width of flower head base

  1–6 mm

• Fruits or seeds

  Number of pappus parts

  11 or more

  Ovary beak length

  3–5 mm

  Ovary length in developed fruit

  6–9 mm

  Seed hair tuft color

  the pappus hairs are white or off-white

  Seed hair tuft details

  the pappus hairs are hooked or barbed

  Seed hair tuft length

  3.5–4 mm

  Seed hair tuft tips

  the pappus hairs are slender

  Seed hairs uniform

  all the pappus hairs are approximately the same length

  Seed tuft type

  the pappus is made of very fine hairs or bristles

  Tuft or plume on fruit

  at least a part of the plume is made up of fine bristles

• Glands or sap

  Leaf blade glands

  the leaf blades have no glandular (translucent) dots or scales

  Sap

  the sap is milky and opaque, and may be white or colored

• Growth form

  Growth form

  the plant has one or more free-standing stems

  Horizontal rooting stem

  there are no stolons

  Plant lifespan

  • the plant is annual, it lacks evidence of previous years' growth
  • the plant is biennial, it appears as either first year (non-reproductive) plants or second year plants with flowers or fruit

  Spines on plant

  the plant has no spines

  Underground organs

  there is a thickened taproot on the plant

• Leaves

  Hairs on underside of leaf blade

  • the underside of the leaf is fuzzy or hairy
  • the underside of the leaf is not hairy, or has very few hairs

  Hairs on upper side of leaf blade

  the upper side of the leaf is not hairy, or has very few hairs

  Leaf arrangement

  alternate: there is one leaf per node along the stem

  Leaf blade base

  the leaf has no petiole

  Leaf blade base shape

  the base of the leaf is cordate (heart-shaped) or sagittate (arrow-shaped)

  Leaf blade edges

  • the edge of the leaf blade has no teeth or lobes
  • the edge of the leaf blade has teeth

  Leaf blade hairs

  NA

  Leaf blade length

  60–150 mm

  Leaf blade shape

  • the leaf blade is oblanceolate (lance-shaped, but with the widest point above the middle of the leaf blade)
  • the leaf blade is ovate (widest below the middle and broadly tapering at both ends)

  Leaf blade tip

  • the tip of the leaf blade is acuminate (tapers to a long, thin point)
  • the tip of the leaf blade is acute (sharply pointed)
  • the tip of the leaf blade is rounded, with no point

  Leaf blade veins

  the leaf blade has one main vein running from the base towards the tip

  Leaf blade width

  120–250 mm

  Leaf disposition

  the lower leaves are larger, toothier, and/or on longer stalks than the upper leaves

  Leaf spines

  there are no spines on the leaf edges

  Leaf stalk

  the leaves have no leaf stalks, but attach directly to the stem

  Leaf stalk length

  At least 0 mm

  Leaf type

  leaves are simple (i.e., lobed or unlobed but not separated into leaflets)

  Specific leaf type

  the leaves are simple (i.e., lobed or unlobed but not separated into leaflets

• Place

  Habitat

  terrestrial

  New England state

  • Maine
  • Massachusetts

  Specific habitat

  • man-made or disturbed habitats
  • meadows or fields

• Scent

  Plant odor

  the plant does not have much of an odor

• Stem, shoot, branch

  Flowering stem cross-section

  the flowering stem is circular, or with lots of small angles

  Leaves on stem

  there is at least one full leaf above the base of the flowering stem

  Stem bloom

  • the stem has a powdery or waxy film on it that can be rubbed away
  • there is no powdery or waxy film on the stem

  Stem internode hair direction

  NA

  Stem internode hair type

  the stem has no hairs between the nodes

  Stem internode hairs

  the stem has no hairs between the nodes

  Stem wings

  the stem does not have wings on it

Wetland status

Not classified

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae