What causes tip burn on lettuce or brown inner leaves on cabbage and other greens?
Tip burn on lettuce and internal browning on cabbage are caused by localized calcium deficiency in the fastest-growing inner tissue — the same mechanism as blossom end rot, but in leafy crops.
On lettuce, calcium deficiency appears as browning or die-back along the very tips and margins of young inner leaves. The outer leaves may look healthy; the problem is concentrated in the newest, most rapidly growing tissue at the center of the head. On cabbage, the symptom is similar but hidden: outer wrapper leaves look fine while inner leaves have brown or glassy-looking margins and a scorched tip — sometimes called internal tipburn or internal browning. Kale, spinach, and Chinese cabbage can show similar tip browning under stress. The affected tissue tends to smell off or rot quickly after harvest because it's already dead.
Calcium moves through the plant only in the water stream pulled from the roots — it travels with transpiration flow. Inner leaves and tightly wrapped heads don't transpire well; their interior surfaces have low airflow and minimal water movement. Even when calcium is abundant in the soil and present throughout the rest of the plant, it simply doesn't reach the innermost, fastest-growing cells in large quantities. Hot weather accelerates growth rate and can outpace calcium delivery. Low humidity and high temperatures also intensify the problem by further limiting transpiration in enclosed leaf tissue.
Consistent, even soil moisture is the most important factor — calcium transport depends on steady water movement through the plant. Avoid letting soil dry significantly between waterings during the heading stage of lettuce or cabbage. Reducing fertilizer nitrogen during head formation can help slow the growth surge that outpaces calcium supply. Some growers apply foliar calcium sprays directly into the head of lettuce during rapid growth, though reaching the innermost leaves is difficult. Spacing plants to improve airflow around heads tends to reduce severity. Looseleaf and butterhead lettuce types are generally less prone than crisphead (iceberg-type) varieties.
Tip burn doesn't indicate the whole head is lost — mild cases affect only a small portion of interior leaves and the remainder of the head is fine. Severe tip burn that extends through multiple layers indicates the crop has been under chronic moisture or temperature stress. Harvest slightly earlier than peak maturity during prolonged heat to get ahead of the damage. Improve irrigation consistency in the bed before the next planting to reduce recurrence.
- LettuceA cool-season leaf crop that thrives in spring and fall, sulks in summer heat.
- CabbageA long-maturing head that splits if you water it wrong at the wrong time.
- KaleThe cold-weather workhorse that improves when everything else quits.
- SpinachA cold-weather green that gives you leaves when almost nothing else will grow.
- AphidSoft, clustered insects on new growth causing curled leaves and sticky honeydew.
- Black RotV-shaped yellow lesions at brassica leaf margins with blackened veins inside — a bacterial disease that moves through the vascular system.
- Blossom End RotDark, sunken, leathery patch on the blossom end of tomato or pepper fruit — a calcium deficiency disorder.
- Gray Mold (Botrytis)Gray-brown fuzzy mold on fruit, flowers, or stems — soft, collapsing tissue beneath the coating in cool, wet conditions.
- Brown Marmorated Stink BugSunken, corky dimples on fruit and pods caused by a mottled brown shield bug feeding through the skin.
- What is that black leathery patch on the bottom of my tomatoes?Blossom end rot is a calcium deficiency at the fruit level, almost always caused by irregular watering rather than a lack of calcium in the soil.
- Why are the leaves on my tomatoes or peppers yellowing between the veins while the veins stay green?Interveinal chlorosis on older, lower leaves is a classic sign of magnesium deficiency — the plant is pulling magnesium from mature tissue to feed new growth.
- We're in a drought — how do I keep my garden going?Mulch, deep infrequent watering, and cutting back on what you're growing are the three adjustments that make the biggest difference during drought conditions.
- What does drought stress actually look like, and how do I know when to water versus when something else is wrong?Drought stress progresses from midday wilting to all-day wilting, leaf curl, and eventually aborted fruit and flowers — the key is catching it before the plant has been dry long enough to abort reproductive structures.