Why are the edges of my plant leaves turning brown and crispy?
Margin scorch is a transport symptom: the edge of a leaf is the end of the plumbing, so it is the first tissue to fail when water or a nutrient cannot reach it. The plant is telling you about supply, not about infection.
The one observation that decides it
Note which leaves are affected. Scorched margins on the OLDEST leaves with the centre still green is potassium deficiency. Scorch on the YOUNGEST inner leaves, while the outer ones stay perfectly green, is tipburn — a calcium transport failure driven by fast growth and fluctuating moisture, not a shortage in the soil. Blackened, limp tips that dried to brown paper within days, all over the plant and after a cold night, are frost damage.
Start from the plant in front of you
7 things it could be
Ordered by how much they can cost you — if the first entry fits what you can see, rule it out before considering the milder ones.
Dark brown or black streaks run along young stems, leaves turn straw-brown and drop suddenly, leaving bare patches that spread outwards. In humid weather a white bloom of spores is visible on the underside of infected leaves.
Conditions: 18–25°C · humidity ≥90% · wet leaves / rainFirst move: Treat, then re-check in 5–7 daysLeaves and shoot tips blacken, go limp and hang down, then dry to brown paper within a few days. Blossom turns brown at the centre and sets no fruit. Split bark and dieback on woody plants may not appear until weeks later.
Conditions: ≤2°CFirst move: Fix the cause, not the leafSeen on: Walnut trees, Lavender
Wilting despite obviously wet soil, yellowing of the lower leaves, and leaf drop. Stems may show soft brown rot at the base, and the soil smells sour or of rotten eggs. Growth stops entirely and the plant becomes an easy target for Phytophthora.
Conditions: humidity ≥90% · wet leaves / rainFirst move: Fix the cause, not the leafGrowing tips distort or die back, young leaves are small with hooked, scorched or curled edges, and hearts of lettuce and cabbage brown internally. In fruit it shows as blossom end rot in tomatoes and peppers and as bitter pit in apples.
Conditions: dry air ≤45%First move: Fix the cause, not the leafYellowing and browning (scorch) of leaf margins on older leaves while the centre stays green, weak stems, and poor, uneven fruit colour and ripening.
Conditions: Spread by handling, insects or soil — not weather-triggeredFirst move: Fix the cause, not the leafPale, papery, blistered or sunken bleached patches on the sun-exposed side of fruit that may later rot; on tree trunks, cracked, sunken dead bark on the south-west side.
Conditions: 32–45°C · dry air ≤50%First move: Fix the cause, not the leafBrown, dry, papery scorching along the margins of the youngest inner leaves, while older outer leaves stay perfectly green. In hearting lettuce it is hidden inside the head until it is cut, and secondary rot often follows in the damaged tissue.
Conditions: ≥24°C · dry air ≤50%First move: Fix the cause, not the leafSeen on: Lettuce