Why are my bay tree's leaves going yellow?

Bay is a tough evergreen that puts up with a great deal and shows almost everything on its leaves. Because most bay trees in Britain live in pots — often the same pot for many years — the commonest cause by a wide margin is simply that the plant has exhausted its compost, but the other three causes look different and need different answers.

Step by step

1. Look at the pattern before doing anything.Uniform pale green to yellow all over usually means nutrient shortage. Yellow with brown crisped margins points to wind or cold scorch. Curled, thickened, yellow-edged leaves means bay sucker. Lower leaves yellowing and dropping while the compost is wet means waterlogging.
2. Check the pot and the roots for the commonest cause.Tip the plant out or look for roots emerging from the drainage holes and circling the surface. A bay that has been in the same pot for three or more years has usually exhausted the compost entirely, and nothing else will fix that.
3. Repot or top-dress in spring.Move it into a pot one size larger with fresh loam-based compost, teasing out the circling roots. On a large specimen that cannot be moved, scrape off the top 50mm of compost and replace it with fresh, and add slow-release fertiliser.
4. Feed through the growing season.A balanced liquid feed every two to three weeks from spring to late summer, or slow-release granules in spring. Bay in a pot is entirely dependent on you for nutrients.
5. Deal with cold wind scorch by moving the plant.Brown crisped edges appearing in late winter and early spring are the wind, not a disease. Move the pot to a more sheltered position, or against a wall, and clip off the worst leaves in spring once new growth starts. The plant recovers.
6. Identify bay sucker by the leaf shape.Bay sucker is a sap-sucking insect that makes the leaf margins thicken, curl downward and turn yellow then brown, often with a white waxy residue on the underside. Pick off and bin affected leaves as they appear; on an established plant the damage is cosmetic.
7. Check the drainage if the compost is wet.Waterlogged bay yellows from the bottom up and drops leaves. Make sure the drainage holes are clear, stand the pot on feet, and let the compost dry out somewhat before watering again. Bay dislikes standing in water.
8. Watch for scale insect on the stems.Small brown limpet-like bumps on the stems and leaf undersides, often with sticky honeydew and black sooty mould below. Rub them off with a cloth, or wipe the stems, and improve airflow around the plant.
9. Prune in late spring or early summer.Bay is a true shrub and does regenerate from old wood, so it can be cut back harder than a Mediterranean subshrub. Use secateurs rather than shears — a hedge trimmer slices the large leaves in half and the cut halves brown off and stay on the plant.
10. Give it a good position and it will look after itself.Full sun to light shade, sheltered from cold drying wind, free-draining compost, regular feeding and watering. Bay in the ground in a mild garden needs almost nothing at all.

Tips

• Bay in a pot needs watering far more often than people expect in summer, and far less in winter. Winter overwatering is a common cause of yellowing.
• A bay standard, or lollipop, is repeatedly clipped and therefore hungrier than a free-growing plant. Feed it accordingly.
• Occasional yellow leaves dropping from a healthy bay are normal — evergreens shed old leaves continuously, usually in spring.
• Bay is hardy in most of the UK but can be cut back by a severe winter. Even a badly damaged plant usually reshoots from the base, so wait until May before giving up on it.

Common mistakes

• Feeding a waterlogged plant — Roots sitting in water cannot take up nutrients, and feeding a drowning plant does nothing. Fix the drainage first.
• Leaving a bay in the same pot for years — It exhausts the compost and becomes pot-bound, which is the single commonest cause of a yellow bay tree.
• Clipping bay with a hedge trimmer — The large leaves are cut in half and the cut edges brown off, so the plant looks damaged for months. Use secateurs.
• Assuming cold has killed a scorched plant in March — Wind-scorched bay looks dreadful and usually recovers fully once growth restarts. Wait until May before cutting anything out.

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