Why Are My Plum Tree Leaves Turning Yellow?

Yellowing leaves on a plum tree are one of the most common problems growers ask about, and for good reason — the symptom can point to a dozen different causes. Plum trees are shallow-rooted stone fruit that are sensitive to soil conditions, nutrient levels and drainage. Getting the diagnosis right early means the difference between a simple spring feed and a much more serious intervention.

Nitrogen deficiency — uniform pale yellowing

A general fade from healthy dark green to pale yellowish green, starting with the older leaves low in the canopy and moving upward, is the classic picture of nitrogen shortage. Plum trees growing under grass competition are especially vulnerable — lawn grass is aggressive at capturing soil nitrogen. In late winter, apply a balanced fruit fertiliser (or sulphate of ammonia at low rates) raked into the soil under the canopy out to the drip line. Never apply nitrogen after midsummer as it promotes soft late growth that frost will damage.

Iron or manganese chlorosis — interveinal yellowing

When the leaf tissue between the veins turns yellow while the veins themselves remain a clear green, you have interveinal chlorosis. In plums this usually indicates iron or manganese deficiency driven by alkaline soil — plums are sensitive to soil pH above 7. The nutrients are present but locked up in an unavailable form. Apply a chelated iron product as a foliar spray for fast response, and address soil pH long-term by incorporating sulphur chips into the root zone over successive seasons. Avoid over-liming near plum trees.

Waterlogging and root oxygen starvation

Plum roots need oxygen. In heavy clay soils or low-lying areas that stay wet for weeks, the roots suffocate and lose the ability to transport nutrients into the canopy. Widespread yellowing that does not improve with feeding, especially after a wet winter or spring, is a strong indicator of waterlogging. Look for grey mottled soil within 30 cm of the surface — a sign of anaerobic conditions. Improve drainage by cutting channels, installing perforated pipe, or mounding the root zone. Young trees can be moved; established trees are harder to rescue.

Magnesium deficiency — orange-yellow interveinal bands

Magnesium deficiency produces a distinctive pattern: yellowing — often with orange or red tints — between the veins of mid-canopy leaves while the leaf margins and veins stay greener for longer. It often appears in late summer on heavily cropping trees, as the developing fruits pull magnesium from the foliage. A foliar spray of Epsom salts (magnesium sulphate) at 200 g per 10 litres of water applied two or three times in summer gives rapid improvement.

Silver leaf disease — early silvery yellowing

Silver leaf (Chondrostereum purpureum) begins as a silvery sheen on individual branches before affected leaves yellow and brown. If yellowing is restricted to particular branches rather than the whole tree and the foliage has a silvery-grey tinge, suspect silver leaf rather than a nutritional problem. Cut back to clean wood (no brown staining in the wood cross-section) and burn affected material immediately.

Natural autumn leaf fall

Plum trees are deciduous and will yellow and drop leaves naturally from late summer onward. If the yellowing is progressing normally in August to October and the tree otherwise looks healthy, this is the expected annual cycle and requires no action.