"How big" is a separate question from "how tall". Most sedums spread far more than they rise, which is why a single plant can colonise a metre of ground while never exceeding 10 cm in height. This page covers typical spread ranges and how to space plants accordingly.
For heights see how tall do sedums grow.
Part of the Complete Sedum Guide.
Spread by growth form
| Growth form | Mature spread from a single plant | Spacing for full cover |
|---|---|---|
| Mat-forming creepers | 45 to 90 cm, indefinite on open ground | 30 cm apart |
| Upright herbaceous (Hylotelephium) | 45 to 60 cm | 45 to 60 cm apart |
| Compact Hylotelephium hybrids (SunSparkler) | 30 to 50 cm | 30 to 40 cm apart |
| Pendant trailers | Stems spreading 60 cm or more, foliage density along them | One per basket |
| Dwarf rosettes and stem-succulents | 20 to 40 cm | 20 to 30 cm apart |
Creeping sedums spread indefinitely; the "mature" spread listed is a realistic 3 to 4 year figure in an open planting where they have room. In paving crevices or on a green roof they spread until they hit a boundary or another colony.
Examples with real dimensions
- Sedum acre — one plant covers 60 cm in three years, more where substrate allows rooting.
- Sedum album 'Coral Carpet' — 45 to 60 cm spread.
- Sedum spurium 'Dragon's Blood' — 45 cm.
- Sedum rupestre 'Angelina' — 45 to 60 cm.
- Sedum kamtschaticum — 30 cm, the tightest of the common creepers.
- Sedum sarmentosum — 90 cm or more; spreads aggressively.
- Hylotelephium telephium 'Autumn Joy' — 60 cm crown width.
- Hylotelephium 'Purple Emperor' — 45 cm.
- Sedum 'Dazzleberry' — 45 cm, about 2 to 3 times its height.
- Sedum morganianum — foliage 15 to 20 cm around the pot, stems hanging to 100 cm.
How big a pot does a sedum need
For the mat-formers, pot size is about the final display rather than the plant's needs. A single S. acre will fill a 20 cm shallow bowl within a season. A S. spurium 'Dragon's Blood' mat for a green-roof section needs at least 30 cm of width per starter plug, planted 30 cm apart.
Hylotelephium in containers need more depth than width. A 30 to 40 cm deep pot for a single mature clump; the tuberous rootstock wants room to bulk down. Wide shallow bowls do not suit this group.
The tender stem-succulents are happy in shallow pots: a 15 to 20 cm bowl is enough for a mature S. rubrotinctum or S. nussbaumerianum.
Pendant trailers (S. morganianum) want a 20 to 25 cm hanging basket. Larger baskets produce more stems; smaller baskets force the plant to stay compact.
When the plant is smaller than expected
A Hylotelephium that is not bulking up after 2 or 3 years is usually in too much shade or has a crowded root ball in a pot too small for it. The cure is more sun or a larger pot. A creeping sedum that is not spreading is almost always in a weed-choked bed; sedums do not compete with faster-growing herbaceous neighbours.
When the plant is much bigger than expected
S. sarmentosum, S. album, and S. acre all spread aggressively on open bare ground. If your planting has escaped its bed, lift the excess in early spring, fragment it, and compost the surplus. They do not have rhizomes or running roots; pulling up the mat removes them cleanly.