Repotting guide

When & how to repot King George aster (Aster amellus 'King George')

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.

Mature size: 50–60 cm tall and 30–40 cm wide (20–24 in tall, 12–16 in wide)

Watch for — Root rot in wet or clay soils: The main risk for this cultivar is sitting in waterlogged soil over winter. Excellent drainage is non-negotiable. Plant on a slight slope or raise the bed if the native soil holds moisture.

How to tell king george aster needs repotting

Repotting on a calendar is less reliable than reading the plant. For king george aster, watch for these signs:

Roots growing out of the drainage holes, or the rootball lifting the plant proud of the rim.
Soil that has shrunk away from the pot sides and no longer holds water.
The pot is unstable because the plant has grown top-heavy.
Old, compacted, broken-down mix that stays wet too long — for a succulent that is a rot risk, so refresh it even if the pot size is fine.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot king george aster

Every 2–3 years, into bone-dry mix. King George aster's growth habit — compact, upright clump-forming herbaceous perennial; slightly more robust than the species average, with sturdy branching stems and grey-green foliage — sets the pace. '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.

What size pot to step king george aster up to

Use a pot only one size up — or even the same pot with fresh gritty mix if the roots have room. King George aster stores water and rots in a large pot of slow-drying soil. A tight terracotta pot that dries fast is far safer than a generous plastic one. Never up-pot a succulent by several sizes.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot king george aster

Spring or summer, while king george aster is in active growth and warm, is best — roots recover fastest then, and the plant is not sitting in cool damp soil. Avoid repotting a succulent in winter dormancy.

Step-by-step: repotting king george aster

Repot dry. Do not water king george aster for several days first. Working with dry roots and dry mix dramatically lowers the rot risk for a succulent.
Pick a snug, fast-draining pot. Choose terracotta one size up at most, with a drainage hole. Have gritty lean to moderately fertile, sharply drained alkaline to neutral soil; ph 6.5–8.0 ready.
Tip it out and clean the roots. Slide the plant out, crumble off the old soil, and trim any black, mushy or dead roots with clean snips.
Pot into dry mix. Set king george aster at its original depth in dry gritty mix, firming gently. Do not bury the stem deeper than it was.
Wait a week before watering. Leave it completely dry and out of harsh sun for about 7 days so any damaged roots callus. Only then water lightly.

Aftercare

Keep king george aster completely dry and out of fierce sun for about a week so any nicked roots callus before they meet moisture; watering a freshly repotted succulent is the classic way to rot it. Then resume the normal lean, dry rhythm. Do not fertilise for about 3 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for king george aster

King George aster wants lean to moderately fertile, sharply drained alkaline to neutral soil; ph 6.5–8.0. Best on chalky, limestone, or gritty loam soils that drain freely after rain. Rich, moist soils cause lush, floppy growth and shorten plant lifespan. Avoid clay without significant grit amendment. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting king george aster — frequently asked questions

How often should you repot king george aster?

Every 2–3 years, into bone-dry mix for king george aster. Repot king george aster every 2–3 years into a snug pot of lean to moderately fertile, sharply drained alkaline to neutral soil; ph 6.5–8.0, ideally in spring or summer. Let it sit in dry soil and do not water for about a week afterwards so any nicked roots can callus. Over-potting and watering straight away is what rots succulents.

What size pot does king george aster need?

When is the best time of year to repot king george aster?

Should you water king george aster after repotting?

No — not straight away. Repot king george aster into dry mix and wait about a week before the first watering so any damaged roots callus over. Watering a freshly repotted succulent is the single most common way to rot one.

Should you fertilise king george aster after repotting?

Not immediately. Wait about 3 weeks after repotting king george aster. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.