Diagnostic Questions

Yellowing has many possible causes: water stress, waterlogging, nutrient shortages, cold roots, pests, disease and simple ageing. Note whether older or newer leaves changed first, whether the yellow is even or between veins, and check soil moisture at root depth. The leaf route walks through the patterns.

Both can cause wilting and yellowing, which is why the soil matters more than the leaves here. Dry soil ten centimetres down suggests underwatering. Cold, wet, sour-smelling soil with soft brown roots suggests overwatering or poor drainage.

Only when the evidence supports it. Rule out water, drainage and root problems first, and ideally confirm with a soil test. A plant with damaged roots cannot use extra nutrients, and excess fertiliser can scorch roots further.

A photo is useful evidence, but rarely enough for a definitive diagnosis. Pattern, soil conditions and growth history fill the gaps, and some diseases can only be confirmed by laboratory testing. Our contact form helps you record all of this.

Not necessarily. Many insects are predators such as ladybird larvae, or simply passing through. Look for direct evidence: insects feeding on damaged tissue, honeydew, cast skins or distorted growth.

Start with a hand texture test, a jar sedimentation test and a drainage test. A home pH kit gives a useful indication, and a laboratory analysis gives reliable nutrient levels. See Investigate the Root Zone.

Usually not. Yellowed, scorched or spotted leaves rarely return to normal. Judge any change by the new growth that appears over the following two to four weeks.

Seek local help for large trees, suspected regulated pests or diseases, rapid decline across many plants, possible contamination, risks to buildings or people, and uncertainty about edible crops.

Home compost heaps often do not reach temperatures high enough to kill all pathogens. Dispose of diseased material according to local guidance, and never move suspected regulated material until you have checked the rules.