Repotting guide

When & how to repot Annual Phlox 'Sugar Stars' (Phlox drummondii 'Sugar Stars')

Also called Annual phlox, Drummond phlox.

More about annual phlox 'sugar stars'

About Annual Phlox 'Sugar Stars'

Phlox drummondii 'Sugar Stars' · also called Annual phlox, Drummond phlox · flowering

'Sugar Stars' is an annual phlox with distinctive star-shaped, lavender-blue petals edged and centred in white. A bushy, free-flowering Texas native annual, it blooms from late spring through summer in dense fragrant clusters, excellent for borders, containers and cutting. It performs best in cool to mild conditions and loves full sun.

Mature size: 20-30 cm tall and 20-25 cm wide.

How to tell annual phlox 'sugar stars' needs repotting

Repotting on a calendar is less reliable than reading the plant. For annual phlox 'sugar stars', watch for these signs:

Roots circling the bottom of the module or pot, or poking out of the drainage holes.
The seedling dries out within a day and growth has visibly stalled.
Roots are white and matted in a tight spiral when you tip the plant out.
It has outgrown its current container for the stage of the season — pot annual phlox 'sugar stars' on before it becomes hard root-bound.

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 annual phlox 'sugar stars'

Pot on seedlings as they grow; not a perennial repot. Annual Phlox 'Sugar Stars'is grown for one season, so the question is really “how often to pot on” — keep moving it up before the roots circle. Bushy, mounded to slightly spreading annual with narrow green leaves and dense terminal clusters of flat, star-tipped flowers..

What size pot to step annual phlox 'sugar stars' up to

Pot annual phlox 'sugar stars' on gradually — a seedling jumped straight into a huge pot sits in cold, wet, airless soil and stalls. Step up one or two sizes at a time as the roots fill each container, finishing in a large final pot or the ground. The aim is roots that never circle and never check.

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 annual phlox 'sugar stars'

Pot annual phlox 'sugar stars' on through the active growing season, whenever roots fill the current container — there is no single date, just "before it becomes root-bound". Avoid potting on during a cold snap.

Step-by-step: repotting annual phlox 'sugar stars'

Pot on before it is root-bound. Check annual phlox 'sugar stars' regularly; move it up as soon as roots reach the edge of the cell or pot, not after they have circled.
Step up one or two sizes. Choose the next container up — not a giant one. Cold, wet, unused soil around a small root system stalls seedlings.
Knock it out gently. Support the stem, tip the pot, and ease the rootball out without breaking it. A little teasing of circled roots at the base is fine.
Pot into rich mix. Set it into fresh fertile, well-drained loam at the same depth (tomatoes are the exception — they can go deeper to root along the stem).
Water in and grow on. Water well, keep it in good light, and resume feeding once it is established and growing again.

Aftercare

Water annual phlox 'sugar stars' in well and keep it in bright light; a freshly potted-on seedling can wilt for a day while roots settle, so do not overcompensate by drowning it. Do not fertilise for about 1 week — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for annual phlox 'sugar stars'

Annual Phlox 'Sugar Stars' wants fertile, well-drained loam. Moist but free-draining, moderately fertile soil rich in organic matter, pH 6.0-7.5. Avoid heavy, waterlogged ground, which encourages root rot. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting annual phlox 'sugar stars' — frequently asked questions

How often should you repot annual phlox 'sugar stars'?

Pot on seedlings as they grow; not a perennial repot for annual phlox 'sugar stars'. Annual Phlox 'Sugar Stars' is a seasonal crop, so you pot it on as a growing plant rather than repotting a perennial. Step seedlings up gradually into fertile, well-drained loam so the roots never circle the cell, ending in a large final container. A root-bound transplant stalls and never fully recovers.

What size pot does annual phlox 'sugar stars' need?

When is the best time of year to repot annual phlox 'sugar stars'?

Can you put annual phlox 'sugar stars' straight into a much bigger pot?

No. Even a fast-growing annual phlox 'sugar stars' should only go up one pot size at a time. A vastly oversized pot holds a reservoir of wet soil the roots cannot reach, which stays cold and soggy and rots the roots — the opposite of what you wanted.

Should you fertilise annual phlox 'sugar stars' after repotting?

Not immediately. Wait about 1 week after repotting annual phlox 'sugar stars'. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.