Why Are the Edges of My Lettuce Leaves Brown?

When the edges of your lettuce leaves turn brown, dry and crispy — especially the younger leaves toward the centre of the head — you are seeing tip burn. It is a frustrating problem because it often strikes just as the head is maturing, ruining the look and inviting rot. The cause is specific and, once you understand it, largely preventable. Let me explain.

What tip burn is

Tip burn is the browning and death of the leaf margins, typically on the newer inner leaves of heading lettuce. It is a physiological disorder, not a disease — no fungus or bug caused it. The tissue at the leaf edge died because it did not get enough calcium during a burst of rapid growth. The damaged margins then often become an entry point for rot, especially in a tight head where air does not circulate, which is why tip burn can quickly turn into a slimy mess inside the head.

The real cause is water and fast growth, not low calcium

Like blossom end rot on fruiting crops, tip burn is rarely about a true calcium shortage in the soil. The problem is that the plant cannot move calcium fast enough to the rapidly growing inner leaf edges, because calcium travels in water and goes preferentially to the outer, more transpiring leaves. When lettuce grows very fast — pushed by heat, heavy nitrogen, or a sudden growth spurt after irregular watering — the inner leaf margins outpace their calcium supply and die. Inconsistent watering makes it worse by interrupting the steady flow of water and calcium.

How to prevent it

The key is steady, moderate growth and even moisture. Water consistently and deeply so the soil stays evenly moist, never swinging between dry and soaked — erratic watering is a major trigger. Avoid over-feeding with nitrogen, which forces the fast soft growth that outruns calcium delivery. Keep the plant cool where you can, since heat drives the rapid growth and water stress behind tip burn; shade during hot spells helps. And don't let lettuce sit overcrowded, as good airflow keeps the heads drier and less prone to the rot that follows tip burn.

Variety and harvest

Some lettuce varieties are far more prone to tip burn than others, and tip-burn-resistant varieties are widely available — a real help if it keeps recurring. Loose-leaf types, with their open structure and better airflow, suffer less than tight crisphead types. Harvesting promptly when heads mature, rather than leaving them to sit and grow on in heat, also reduces losses. Affected outer leaves can be peeled away and the rest of the head used, but prevention through steady watering, moderate feeding and cool conditions is far better than salvaging damaged heads.