Hydrangea: lower leaves turning yellow

What it is likely to be on hydrangea

1. Lime-induced chlorosis

   Candidate 1occasional on this plant

   ·source

   Sourced guidancemoderate confidence

   • Royal Horticultural Society: Hydrangea — cultivation
   • Home and Garden Information Center — Clemson Cooperative Extension: Hydrangea problems

   Checked 2026-08-13

   Yellowing between the veins of the YOUNGEST leaves while the veins stay green. The soil usually contains plenty of iron; what is wrong is that the pH is too high for the plant to take it up. Adding iron to the soil without correcting the pH changes nothing.

   Points towards it

   • · iron cannot move within the plant, so shortage shows as yellow tissue held in a green vein network
   • · the newest leaves are affected first, which is the signature that separates an uptake problem from a shortage of something the plant can move
   • · it tracks the pH of the ground it is planted in

   Argues against it

   • · yellowing on the oldest leaves only is a mobile-nutrient or ageing pattern; iron is immobile and cannot produce it — this rules it out entirely.
   • · an evenly yellow leaf with the veins going yellow too is not an iron pattern

   Check this next

   Look at the newest leaves at the shoot tips and ignore the flowers entirely. Hydrangea flower colour follows soil pH through aluminium and tells you nothing about the foliage; yellow NEW leaves with a green vein network on chalky ground or after years of hard tap water is iron that the plant cannot reach.

   What to do now

   Test the soil pH before reaching for anything. Where it is genuinely alkaline, mulch annually with composted bark or leafmould and water with stored rainwater — a sequestered iron feed will green it up for one season and the yellowing will return, because the pH that caused it has not moved.

   ·source

   Sourced guidancemoderate confidence

   • Royal Horticultural Society: Lime-induced chlorosis

   Checked 2026-08-13

2. Underwatering

   Candidate 2very common on this plant

   ·source

   Sourced guidancehigh confidence

   • Royal Horticultural Society: Hydrangea — cultivation

   Checked 2026-08-13

   Easier to correct than overwatering and easily confused with it, because a plant short of water and a plant drowning both wilt. The distinguishing observation is not the plant at all — it is the compost, and it takes two seconds to check.

   Points towards it

   • · a hydrangea carries more leaf area than its roots can supply on a dry summer day, and it is the first shrub in a border to feel it
   • · a shrub short of water sheds its oldest leaves first to protect the newest
   • · the yellowing follows a hot dry spell rather than appearing gradually

   Argues against it

   • · the ground is wet, so the plant is not short of water — this rules it out entirely.

   Check this next

   Go out and look at it first thing in the morning rather than in the afternoon. A hydrangea that has flagged in the heat and stood back up overnight was merely thirsty for an hour; one that is still limp with yellowing lower leaves at breakfast has been genuinely short of water for days, and the name of the plant is a fair description of what it wants.

   What to do now

   Water heavily and infrequently rather than little and often — two full cans into the root zone soaks the depth a hydrangea roots at, where a daily sprinkle wets only the mulch. Then mulch thickly, and if it is in a pot in full sun accept that it will need this every day in July.

   ·source

   Sourced guidancehigh confidence

   • Royal Horticultural Society: Watering trees and shrubs

   Checked 2026-08-13

Narrow it down

This page lists everything at once, which is the right shape for reading and the wrong shape for deciding. The interactive tool asks one question at a time, starting with whichever would separate these causes fastest, and stops as soon as further answers would not help.

Opens with the plant and the symptom already set. Nothing you answer is stored or sent anywhere — the answers live in the address bar and nowhere else.

What this does not cover

These are the causes GrowingHQ holds rules for on hydrangea — not every cause there is. Where several problems look alike, the honest answer is often that they cannot be told apart by eye, and a page that named one would be guessing. If none of the above fits, the general lower leaves turning yellow page lists causes across all plants, and the Hydrangea profile lists the problems it is prone to.