Fertilising guide
How to fertilise Black Lily Magnolia (Magnolia liliiflora 'Nigra')— schedule & NPK
Also called black lily magnolia, dark purple magnolia, purple tulip magnolia.
More about black lily magnolia
About Black Lily Magnolia
Magnolia liliiflora 'Nigra' · also called black lily magnolia, dark purple magnolia · flowering
Magnolia liliiflora 'Nigra' is a compact deciduous shrub bearing exceptionally deep wine-purple, multi-petalled flowers with pale interiors. Blooming in mid-spring and often reflowering sporadically into summer, it is one of the most intensely coloured magnolias available. It suits small gardens and provides a long ornamental season.
Growth habit: Compact, upright, multi-stemmed deciduous shrub
Watch for — Insufficient flowering: Poor flower set is often caused by alkaline soil pH, lack of sun, or high-nitrogen feeding. Test soil pH and acidify if above 6.5; reposition if shaded by neighbouring plants.
What fertiliser black lily magnolia actually wants — and why
Black Lily Magnolia 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 black lily magnolia: 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 black lily magnolia, 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 black lily magnolia:
Feed with an ericaceous or acid-lover fertiliser in early spring as buds swell, and again with a potassium-rich feed (e.g., sulphate of potash) in July to encourage the secondary flush of flowering. Avoid nitrogen-heavy fertilisers after midsummer. 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 black lily magnolia 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 black lily magnolia
Follow the ericaceous product's own rate — these are formulated for the plant, so the dilution on the label is right for black lily magnolia. The variable that actually matters is pH, not concentration.
Feeding always goes onto already-damp soil, never dry roots — water black lily magnolia first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the black lily magnolia watering schedule.
Signs you are over-feeding black lily magnolia
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for black lily magnolia:
- 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 black lily magnolia
- 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 black lily magnolia care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush black lily magnolia 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 black lily magnolia
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 black lily magnolia — frequently asked questions
What fertiliser does black lily magnolia 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. Black Lily Magnolia 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 black lily magnolia?
Feed with an ericaceous or acid-lover fertiliser in early spring as buds swell, and again with a potassium-rich feed (e.g., sulphate of potash) in July to encourage the secondary flush of flowering. Avoid nitrogen-heavy fertilisers after midsummer. Feed with an ericaceous or acid-lover fertiliser in early spring as buds swell, and again with a potassium-rich feed (e.g., sulphate of potash) in July to encourage the secondary flush of flowering. Avoid nitrogen-heavy fertilisers after midsummer. 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 black lily magnolia?
Follow the ericaceous product's own rate — these are formulated for the plant, so the dilution on the label is right for black lily magnolia. The variable that actually matters is pH, not concentration.
What does over-feeding black lily magnolia 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 black lily magnolia 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 black lily magnolia?
Flush black lily magnolia 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
- Black Lily Magnolia care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water black lily magnolia — 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 medusa orchid
- How to fertilise rothschild's bulbophyllum
- How to fertilise lobb's bulbophyllum
- All 6887 fertilising guides in the Growli library