Fertilising guide

How to fertilise Lobster Flower (Plectranthus neochilus)— schedule & NPK

Also called Lobster Flower, Blue Coleus, Spur Flower.

More about lobster flower

About Lobster Flower

Plectranthus neochilus · also called Lobster Flower, Blue Coleus · flowering

Plectranthus neochilus is a low-growing, mat-forming, semi-succulent perennial native to southern Africa, instantly recognisable by its lime-green, broad leaves with coppery-purple undersides and its strong, pungent aroma that is widely used as a natural cat and dog deterrent in gardens. It produces upright spikes of soft purple-blue tubular flowers through much of the growing season. The most important care fact is that it is remarkably drought tolerant due to its succulent stems, and overwatering is the primary cause of failure — water only when the soil is fully dry. Multiple sources classify the genus pattern as non-toxic to dogs and cats, and Mountain Crest Gardens specifically lists P. neochilus as pet-safe.

Growth habit: Sprawling, mat-forming semi-succulent groundcover with upright flowering stems; spreads readily by stem layering.

What fertiliser lobster flower actually wants — and why

Lobster Flower flowers best on poor soil — feed it and you get a lush leafy plant with very few blooms, the exact opposite of what you want.

Little or nothing. Rich, especially nitrogen-rich, soil pushes foliage at the expense of flowers in this plant — lean ground is the technique, not a deficiency.

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 lobster flower: 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 lobster flower, 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 lobster flower:

Apply a balanced liquid fertiliser at half-strength once monthly during spring and summer; excessive nitrogen encourages lush, floppy growth at the expense of flowers. In practice: no routine feeding at all for lobster flower — at most a thin compost mulch for soil structure, never a flowering or nitrogen feed.

The dormant-season rule matters more than the exact interval: skip feeding entirely when lobster flower 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 lobster flower

None is the correct answer for lobster flower. The flower-versus-foliage trade-off is the whole point: hold back and you get the display.

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

Signs you are over-feeding lobster flower

Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for lobster flower:

Abundant leafy growth and very few flowers (the classic over-rich symptom).
Soft, floppy stems and a sprawling, leafy habit.
Scorched edges and salt crust if it has been fed in a container.

Signs you are under-feeding lobster flower

Effectively never an issue — these plants flower on poverty.
Only on genuinely dead soil: weak, thin growth and few blooms.
A short-lived plant in completely spent container compost.

If the symptoms point at watering, light or roots rather than nutrition, the full lobster flower care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

If lobster flower has accidentally been fed and is all leaf, a plain-water flush plus a move to leaner soil resets it; otherwise no flushing is needed because you are not feeding it.

Organic vs synthetic feeds for lobster flower

Organic options

A thin compost mulch for soil structure is the absolute most; mostly, give it nothing. UK/US: leave it lean — no manure, no liquid feed. Poor soil is the active ingredient here.

Synthetic / liquid feeds

None. Synthetic feeds, particularly anything with appreciable nitrogen, directly suppress flowering in lobster flower.

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 lobster flower — frequently asked questions

What fertiliser does lobster flower need?

Little or nothing. Rich, especially nitrogen-rich, soil pushes foliage at the expense of flowers in this plant — lean ground is the technique, not a deficiency. Lobster Flower flowers best on poor soil — feed it and you get a lush leafy plant with very few blooms, the exact opposite of what you want.

How often should I feed lobster flower?

Apply a balanced liquid fertiliser at half-strength once monthly during spring and summer; excessive nitrogen encourages lush, floppy growth at the expense of flowers. Apply a balanced liquid fertiliser at half-strength once monthly during spring and summer; excessive nitrogen encourages lush, floppy growth at the expense of flowers. In practice: no routine feeding at all for lobster flower — at most a thin compost mulch for soil structure, never a flowering or nitrogen feed.

What strength of feed for lobster flower?