Why is my lettuce bitter?

Where bitterness comes from

Lettuce produces sesquiterpene lactones — chiefly lactucin and lactucopicrin — as a defence. The concentration rises with heat, with age, with water stress, and sharply once the plant begins to flower. It is the same compound family that gives chicory and endive their bite; lettuce simply has less of it until something goes wrong.

What raises it

• Heat. A week above 25 °C will do it, even in a mild variety.
• Age. Over-mature heads are bitter heads. This is the most common cause at home.
• Drought stress. Shallow roots, so dry spells hit hard.
• Bolting. The moment the stem stretches, bitterness climbs.
• Nitrogen shortage. Pale, slow, bitter plants are often simply underfed.

What genuinely helps

• Harvest younger. Cut leaf lettuce at 5–6 weeks rather than waiting for size. Heads are best the day they firm up, not a week later.
• Harvest in the morning. Sugar content is highest and the leaves are turgid.
• Chill immediately. Plunge into cold water for five minutes. This does not remove the lactones but it measurably softens the perception of them.
• Keep water even. Mulch, and water before the soil dries rather than after.
• Shade in heat, as with bolting — the two problems share a cause.
• Pick a mild variety on purpose. Flavour is documented per variety in our catalogue; the mildest are listed below.

Dressing covers a lot

Fat, salt and acid blunt bitterness: oil, a little salt, lemon or vinegar. That is why the same leaf tastes fine dressed and harsh plain. Cooking removes most of it — bitter lettuce is good braised or in soup.

Varieties documented as mild

The short version

Bitterness is a heat-and-age problem, not a defect in the seed. Grow it cooler, cut it younger, water it evenly, and choose a variety whose flavour record actually says mild.

Questions

All 110 lettuce varieties →  ·  Browse the catalogue