Fertilising guide

How to fertilise King George aster (Aster amellus 'King George')— schedule & NPK

Also called King George aster, King George Italian aster.

More about king george aster

About King George aster

Aster amellus 'King George' · also called King George aster, King George Italian aster · flowering

'King George' is a long-established cultivar of Italian aster, prized for its large, rich violet-blue daisy flowers with deep golden-yellow disc centres produced freely from late August through September. It is compact, reliably mildew-resistant, and thrives in alkaline, well-drained soils. An AGM-awarded plant from the Royal Horticultural Society, it is one of the finest selections of A. amellus for late-season colour.

Growth habit: Compact, upright clump-forming herbaceous perennial; slightly more robust than the species average, with sturdy branching stems and grey-green foliage

What fertiliser king george aster actually wants — and why

King George aster 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 king george aster: 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 king george aster, 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 king george aster:

One application of balanced granular fertiliser in early spring is sufficient. Avoid high-nitrogen or rich compost mulches — they encourage vegetative growth at the expense of flowers and plant longevity. In practice: no routine feeding at all for king george aster — 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 king george aster 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 king george aster

None is the correct answer for king george aster. 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 king george aster first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the king george aster watering schedule.

Signs you are over-feeding king george aster

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

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 king george aster

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 king george aster care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

If king george aster 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 king george aster

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 king george aster.

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 king george aster — frequently asked questions

What fertiliser does king george aster 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. King George aster 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 king george aster?

One application of balanced granular fertiliser in early spring is sufficient. Avoid high-nitrogen or rich compost mulches — they encourage vegetative growth at the expense of flowers and plant longevity. One application of balanced granular fertiliser in early spring is sufficient. Avoid high-nitrogen or rich compost mulches — they encourage vegetative growth at the expense of flowers and plant longevity. In practice: no routine feeding at all for king george aster — at most a thin compost mulch for soil structure, never a flowering or nitrogen feed.

What strength of feed for king george aster?