Fertilising guide

How to fertilise Cape Leadwort (Blue Plumbago) (Plumbago auriculata)— schedule & NPK

Also called Cape leadwort, Blue plumbago, Cape plumbago, Blue jasmine, Sky flower.

More about cape leadwort (blue plumbago)

About Cape Leadwort (Blue Plumbago)

Plumbago auriculata · also called Cape leadwort, Blue plumbago · flowering

Cape leadwort is a vigorous, frost-tender South African shrub prized for sky-blue phlox-like blooms from summer into autumn. Give it full sun, moderate water and well-drained soil; hard-prune in late winter. It is not ASPCA-listed but contains plumbagin, a skin irritant, so treat it as mildly toxic and verify with a vet.

Growth habit: Sprawling, semi-climbing evergreen-to-deciduous shrub with long, lax stems that can be left to mound, trained up a trellis or wall, or clipped into a looser hedge. Flowers form on new growth, so timing of pruning matters.

What fertiliser cape leadwort (blue plumbago) actually wants — and why

Cape Leadwort (Blue Plumbago) is feeding to flower, not to grow leaves — it needs a higher-phosphorus / specialist bloom feed, given little and often, to set and hold its display.

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 cape leadwort (blue plumbago): 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 cape leadwort (blue plumbago), 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 cape leadwort (blue plumbago):

Feed monthly through spring and summer with a balanced liquid fertiliser to fuel continuous flowering; a high-potash bloom feed can boost flower count. Stop feeding in autumn and winter while growth slows. The pattern that matters: feed little and often through active growth and budding — monthly — and ease right off during the rest period that triggers the next flush.

The dormant-season rule matters more than the exact interval: skip feeding entirely when cape leadwort (blue plumbago) 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 cape leadwort (blue plumbago)

Very dilute — quarter strength, the classic "weakly, weekly" approach for cape leadwort (blue plumbago). These plants have fine roots that scorch easily and a steady trickle beats an occasional strong dose for flowering.

Feeding always goes onto already-damp soil, never dry roots — water cape leadwort (blue plumbago) first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the cape leadwort (blue plumbago) watering schedule.

Signs you are over-feeding cape leadwort (blue plumbago)

Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for cape leadwort (blue plumbago):

Lush green leaves but few or no flowers (too much nitrogen).
Brown, scorched leaf tips and edges — a classic fine-root burn.
White salt crust on the medium or pot, and stalled buds.
Bud blast: buds forming then shrivelling and dropping.

Signs you are under-feeding cape leadwort (blue plumbago)

Sparse or no flowering despite good light and the right season.
Smaller, paler new leaves and a generally weak, tired plant.
Flowers that are smaller or fade faster than they should.

If the symptoms point at watering, light or roots rather than nutrition, the full cape leadwort (blue plumbago) care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

Specialist and bloom feeds leave salts that scorch fine roots — flush cape leadwort (blue plumbago) thoroughly with plain water until it runs clear every 4-6 weeks in the feeding season, and always between feeds for orchids.

Organic vs synthetic feeds for cape leadwort (blue plumbago)

Organic options

Gentler options exist: a dilute seaweed feed (mildly potassium-rich) or worm-casting tea. UK: Westland seaweed, or a dilute tomato feed like Tomorite for bud-formers; US: Espoma Orchid! / Violet! or Neptune's Harvest. Lower burn risk, slower response.

Synthetic / liquid feeds

A species-matched bloom feed at quarter strength — UK: Baby Bio Orchid / African Violet food, or a high-potash Tomorite/Phostrogen for budding bloomers; US: Miracle-Gro Orchid or Bloom Booster, Schultz African Violet.

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 cape leadwort (blue plumbago) — frequently asked questions

What fertiliser does cape leadwort (blue plumbago) need?

A higher-phosphorus "bloom" formula or a species-specific feed (orchid food, African violet food, or a tomato-style high-potash/phosphorus liquid). A high-nitrogen general feed gives you lush leaves and almost no flowers. Cape Leadwort (Blue Plumbago) is feeding to flower, not to grow leaves — it needs a higher-phosphorus / specialist bloom feed, given little and often, to set and hold its display.

How often should I feed cape leadwort (blue plumbago)?

Feed monthly through spring and summer with a balanced liquid fertiliser to fuel continuous flowering; a high-potash bloom feed can boost flower count. Stop feeding in autumn and winter while growth slows. Feed monthly through spring and summer with a balanced liquid fertiliser to fuel continuous flowering; a high-potash bloom feed can boost flower count. Stop feeding in autumn and winter while growth slows. The pattern that matters: feed little and often through active growth and budding — monthly — and ease right off during the rest period that triggers the next flush.

What strength of feed for cape leadwort (blue plumbago)?

What does over-feeding cape leadwort (blue plumbago) look like?

Lush green leaves but few or no flowers (too much nitrogen). Brown, scorched leaf tips and edges — a classic fine-root burn. White salt crust on the medium or pot, and stalled buds. Bud blast: buds forming then shrivelling and dropping. Using an ordinary high-nitrogen houseplant feed on cape leadwort (blue plumbago) is the headline mistake — you get a healthy-looking plant that simply refuses to bloom. The second is feeding through the rest period and breaking the dormancy cue it needs to set buds.

Should I flush the soil of cape leadwort (blue plumbago)?