Repotting guide

When & how to repot Crystal Palace lobelia (Lobelia erinus 'Crystal Palace')

Also called Crystal Palace lobelia, edging lobelia, trailing lobelia, annual lobelia.

More about crystal palace lobelia

About Crystal Palace lobelia

Lobelia erinus 'Crystal Palace' · also called Crystal Palace lobelia, edging lobelia · flowering

Crystal Palace lobelia is a compact, mounding cultivar of Lobelia erinus bearing a dense carpet of deep navy-blue flowers with a white eye above dark bronze-green foliage. A cool-season annual, it thrives in bright conditions with consistent moisture and is ideal for edging, containers and hanging baskets. Contains lobeline alkaloids — treat as toxic to pets.

Mature size: 10-15 cm tall, 20-30 cm spread

How to tell crystal palace lobelia needs repotting

Repotting on a calendar is less reliable than reading the plant. For crystal palace lobelia, 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 crystal palace lobelia 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 crystal palace lobelia

Pot on seedlings as they grow; not a perennial repot. Crystal Palace lobeliais grown for one season, so the question is really “how often to pot on” — keep moving it up before the roots circle. Compact mounding annual — low spreading cushion.

What size pot to step crystal palace lobelia up to

Pot crystal palace lobelia 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 crystal palace lobelia

Pot crystal palace lobelia 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 crystal palace lobelia

Pot on before it is root-bound. Check crystal palace lobelia 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 moist, fertile, free-draining loam or all-purpose potting compost 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 crystal palace lobelia 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 crystal palace lobelia

Crystal Palace lobelia wants moist, fertile, free-draining loam or all-purpose potting compost. Performs best in fertile soil with good moisture retention and reasonable drainage. In containers use a quality peat-free multipurpose compost mixed with a little perlite for drainage. Avoid heavy clay without amendment, as stagnant moisture encourages root rot and basal stem 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 crystal palace lobelia — frequently asked questions

How often should you repot crystal palace lobelia?

Pot on seedlings as they grow; not a perennial repot for crystal palace lobelia. Crystal Palace lobelia is a seasonal crop, so you pot it on as a growing plant rather than repotting a perennial. Step seedlings up gradually into moist, fertile, free-draining loam or all-purpose potting compost 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 crystal palace lobelia need?

When is the best time of year to repot crystal palace lobelia?

Can you put crystal palace lobelia straight into a much bigger pot?

No. Even a fast-growing crystal palace lobelia 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 crystal palace lobelia after repotting?

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