Why Are My Grapevine Leaves Turning Yellow?

Yellowing grapevine leaves are one of the most common concerns for home growers, and the good news is that most causes are treatable once you identify which pattern of yellowing you are dealing with. The colour change can start at the leaf margins, between the veins, or uniformly across the whole canopy — and each pattern points to a different underlying problem. Understanding what you are seeing is the first step toward restoring the vine to full health.

Iron or magnesium deficiency causing interveinal chlorosis

When the tissue between the leaf veins turns pale yellow while the veins stay green, the vine is suffering from iron or magnesium deficiency — or more accurately from alkaline soil conditions that lock those nutrients out. Grapevines are sensitive to high pH and grow best in slightly acidic to neutral soils (pH 6.0–7.0). Apply chelated iron as a foliar spray or soil drench, and test soil pH. Incorporating sulphur chips over time can gradually bring alkaline soils into the right range.

Nitrogen deficiency causing pale overall yellowing

A general fade from deep green to pale yellow-green starting with the oldest basal leaves signals nitrogen shortage. Vines grown in very sandy soil, in competition with grass, or left unfed for several years commonly show this. Apply a balanced fertiliser in early spring as the buds swell — a product designed for fruiting plants works well. Avoid heavy nitrogen doses in summer as they encourage leafy growth at the expense of fruit ripening.

Waterlogging and root stress

Grapevine roots need well-drained soil. In a poorly drained position, especially after a wet winter or spring, roots suffocate and stop supplying nutrients to the canopy. The leaves turn yellow and may eventually brown at the margins despite the soil appearing moist. If the problem follows heavy rainfall, improving drainage around the base of the vine is more important than any feeding programme. Raised beds or mounded planting positions help enormously in gardens with clay or compacted soils.

Downy mildew causing pale patches

Early downy mildew infection produces pale, oily-looking yellow patches on the upper leaf surface, often with a white fuzzy growth on the underside. If the yellowing is irregular and blotchy rather than uniform, check the underside of the leaf carefully. Treat with a copper-based fungicide and improve air circulation by thinning dense canopy growth.

Natural autumn leaf change

Grapevines are deciduous and turn vivid shades of yellow, orange, and red in autumn before leaf drop. If yellowing begins in late September and the rest of the vine looks healthy and cropped well, this is entirely normal seasonal behaviour. No action is needed; the vine is simply preparing for dormancy.