Fertilising guide
How to fertilise Oxydendrum arboreum (Oxydendrum arboreum)— schedule & NPK
Also called Sourwood, Sorrel Tree, Lily-of-the-valley Tree.
More about oxydendrum arboreum
About Oxydendrum arboreum
Oxydendrum arboreum · also called Sourwood, Sorrel Tree · flowering
Sourwood is a graceful deciduous tree offering three seasons of interest: drooping sprays of fragrant white lily-of-the-valley-like flowers in summer, exceptional crimson autumn foliage, and persistent silvery seed capsules. A member of the heath family, it demands acid, moist, well-drained soil and full sun to part shade, rewarding patience with outstanding ornamental value.
Growth habit: Slow-growing, slender deciduous tree with a narrow, pyramidal to rounded crown and gracefully arching, drooping branch tips. Often develops an irregular, picturesque outline with age, and deeply furrowed grey-brown bark.
Watch for — Chlorosis on alkaline soil: As an acid-lover, it yellows badly and declines on chalky or high-pH ground. Plant only in genuinely acid soil and feed with ericaceous fertiliser and chelated iron if needed.
What fertiliser oxydendrum arboreum actually wants — and why
Oxydendrum arboreum is an acid-loving plant — it can only take up nutrients in acidic soil, so the feed itself matters less than using an ericaceous formula and never liming.
An ericaceous (acidic) fertiliser, formulated to keep the soil pH low and supply iron and trace elements in a form acid-loving roots can absorb. Ordinary feeds and any lime lock out iron and yellow the leaves.
For the language behind the three numbers on the bottle — what nitrogen, phosphorus and potassium each do — see the NPK ratio explained entry. The short version for oxydendrum arboreum: match the feed to the job the plant is doing right now, not to a generic “plant food” on the shelf.
How often to feed oxydendrum arboreum, and which months
Feeding only earns its keep while the plant is in active growth and can use the nutrients — pour feed into a dormant or low-light plant and it simply builds up as root-burning salt. For oxydendrum arboreum:
Feed as an acid-loving plant: an ericaceous (rhododendron/azalea) fertiliser in early spring plus a leaf-mould or pine-needle mulch. Avoid lime and alkaline feeds; if foliage yellows between the veins, apply chelated iron and acidify the soil. In practice: an ericaceous feed in spring as growth resumes, repeated through the main growing months; never apply lime, bonemeal or wood ash, which raise pH.
The dormant-season rule matters more than the exact interval: skip feeding entirely when oxydendrum arboreum is resting. For the wider context on indoor feeding rhythms across the seasons, the houseplant fertiliser schedule walks through the year month by month.
What strength to mix for oxydendrum arboreum
Follow the ericaceous product's own rate — these are formulated for the plant, so the dilution on the label is right for oxydendrum arboreum. The variable that actually matters is pH, not concentration.
Feeding always goes onto already-damp soil, never dry roots — water oxydendrum arboreum first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the oxydendrum arboreum watering schedule.
Signs you are over-feeding oxydendrum arboreum
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for oxydendrum arboreum:
- Brown, scorched leaf margins from too strong or too frequent a dose.
- White salt crust on the soil surface.
- Soft, lush growth that fruits or flowers poorly.
Signs you are under-feeding oxydendrum arboreum
- Yellowing leaves with green veins (iron chlorosis from high pH).
- Weak growth, poor cropping and an overall pale, stressed look.
- Stunted new shoots in spring despite adequate water and light.
If the symptoms point at watering, light or roots rather than nutrition, the full oxydendrum arboreum care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush oxydendrum arboreum with rainwater (not hard tap water, which raises pH) if salts build up; better still, mulch with pine needles or composted bark and water with rainwater to hold the acidity.
Organic vs synthetic feeds for oxydendrum arboreum
Organic options
Composted pine bark, pine-needle mulch, used coffee grounds and an organic ericaceous feed gently maintain acidity. UK: Vitax or Westland Ericaceous; US: Espoma Holly-tone or Dr. Earth Acid Lovers. Slow, soil-improving, hard to overdo.
Synthetic / liquid feeds
A liquid or granular ericaceous feed — UK: Miracle-Gro Ericaceous, Vitax or Westland; US: Miracle-Gro Acid-Loving Plant Food or Espoma Holly-tone. Pair with rainwater and an acidic mulch for it to work.
Brand names are examples, not endorsements, and UK and US ranges differ — check the label’s own NPK and dilution rate, since formulations change.
Fertilising oxydendrum arboreum — frequently asked questions
What fertiliser does oxydendrum arboreum need?
An ericaceous (acidic) fertiliser, formulated to keep the soil pH low and supply iron and trace elements in a form acid-loving roots can absorb. Ordinary feeds and any lime lock out iron and yellow the leaves. Oxydendrum arboreum is an acid-loving plant — it can only take up nutrients in acidic soil, so the feed itself matters less than using an ericaceous formula and never liming.
How often should I feed oxydendrum arboreum?
Feed as an acid-loving plant: an ericaceous (rhododendron/azalea) fertiliser in early spring plus a leaf-mould or pine-needle mulch. Avoid lime and alkaline feeds; if foliage yellows between the veins, apply chelated iron and acidify the soil. Feed as an acid-loving plant: an ericaceous (rhododendron/azalea) fertiliser in early spring plus a leaf-mould or pine-needle mulch. Avoid lime and alkaline feeds; if foliage yellows between the veins, apply chelated iron and acidify the soil. In practice: an ericaceous feed in spring as growth resumes, repeated through the main growing months; never apply lime, bonemeal or wood ash, which raise pH.
What strength of feed for oxydendrum arboreum?
Follow the ericaceous product's own rate — these are formulated for the plant, so the dilution on the label is right for oxydendrum arboreum. The variable that actually matters is pH, not concentration.
What does over-feeding oxydendrum arboreum look like?
Brown, scorched leaf margins from too strong or too frequent a dose. White salt crust on the soil surface. Soft, lush growth that fruits or flowers poorly. Feeding oxydendrum arboreum an ordinary fertiliser, or growing it in hard tap water / limey soil, is the defining mistake — it triggers lime-induced chlorosis (yellow leaves, green veins) no amount of feeding fixes until the pH comes down.
Should I flush the soil of oxydendrum arboreum?
Flush oxydendrum arboreum with rainwater (not hard tap water, which raises pH) if salts build up; better still, mulch with pine needles or composted bark and water with rainwater to hold the acidity.
Keep reading
- Oxydendrum arboreum care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water oxydendrum arboreum — the watering schedule
- The houseplant fertiliser schedule — feeding through the year
- NPK ratio explained — what the three numbers on the bottle mean
- How to fertilise peace lily
- How to fertilise bird of paradise
- How to fertilise hoya
- All 5561 fertilising guides in the Growli library