Swamp isotome – info, planting, care and tips

Swamp isotome (Isotoma fluviatilis)
Swamp isotome (Isotoma fluviatilis)

Swamp isotome is a carpet-forming ground cover with a long flowering time. Here you will find useful planting and care tips for the blue star creeper.

Profile of swamp isotome:

Scientific name: Isotoma fluviatilis

Plant family: bellflower family (Campanulaceae)

Other names: blue star creeper

Planting time: spring

Flowering period: May until October

Location: sunny to partially shaded

Soil quality: loamy, nutrient rich

These information are for temperate climate!

Use in: flower beds, ground cover, group planting, planters, underplanting, borders, flower garden, natural garden, rose garden, potted garden

Winter hardiness: hardy, USDA Plant Hardiness Zones: 7 (-15 °C / +5 °F)

Bee and insect friendly: Yes

Plant characteristics and classification of swamp isotome

Plant order, origin and occurrence of swamp isotome

The swamp isotome belongs to the bellflower family (Campanulaceae). In addition to swamp isotome it is also known as blue star creeper. The botanical name has also changed several times. Today it is called Isotoma fluviatilis, but many perennial nurseries still sell it as Pratia pedunculata or Laurentia fluviatilis. The home of the swamp isotome is on the southeast coast of Australia and Tasmania, where it prefers to settle in moist, acidic locations.

Characteristics of swamp isotome


Swamp isotome grows as a perennial, hardy perennial. By means of runners, it forms dense, flat, mat-like leaf carpets relatively quickly. Even with flowers, the plants are only 5 centimeters (2 in) high.


The evergreen leaves of the blue star creeper are round to egg-shaped and can grow up to 9 millimeters (0.36 in) long.


Swamp isotome is a real permanent bloomer. From May to October light blue, sometimes almost white star-shaped flowers appear, which sit on short, about 5 centimeters (2 in) long stems above the foliage. They are small and no more than 7 millimeters (0.28 in) in diameter.


The flowers sometimes form small, fleshy berry fruits that are reddish to purple in color.

Swamp isotome – cultivation and care


The blue star creeper grows in sunny to shady or even partially shaded places. That depends on the water storage capacity of the soil.


Fresh, nutrient-rich soils are ideal for the swamp isotome. What the plants don’t like are locations that are too dry and very calcareous. The soil should hold water well, but not be waterlogged. If the subsurface is permanently fresh, as is the case with loamy soils, even very sunny places are no problem. On the other hand, sandy soils that dry out quickly should be in partial shade if you don’t want to water permanently.

Planting swamp isotome

For the blue star creeper, planting in spring is recommended. This leaves enough time for it to take root before winter so that it can safely survive the cold season. Always place several specimens, in small or large groups, with a distance of 20 centimeters (8 in).

Care / Watering / Pruning

Swamp isotomes are very easy to care for if they are in the right location. You will quickly notice whether they feel good: if the blue star creeper spreads, everything is fine. It needs a lot of additional watering in too dry places. If it grows too lush, you can control it simply by cutting off. Cutting or mowing does not damage the mats either, rather it seems to strengthen their vigor.


Regular dividing of the plant is not necessary to keep it vigorous, vital and blooming. However, you can easily propagate swamp isotome by cutting off pieces. It is best to do this in spring, as this is the best time to plant.


Swamp isotome can be easily propagated by dividing it. Simply cut off sections with the spade, remove them from the ground and replant them elsewhere.

Diseases and pests

The blue star creeper is a very robust plant, which at most can be troubled by a wrong location. So if it withers or even disappears, you should give it another place next time. Swamp isotome can also be in trouble the winter sun, but shading the shoots helps. Otherwise, pests and plant diseases are not an issue.


The extremely vigorous blue star creeper is hardy down to -15 °C / +5 °F. It is not so much the cold that troubles it, but the winter sunshine. The plants appreciate it if you protect them from this with a shade, such as a fleece. They survive the winter uncovered, but sometimes look quite worn out. But don’t worry, it usually gets better in the course of spring.

Use in the garden

The ground cover is wonderfully suitable for greening large areas and covering them with flowers throughout the summer and into autumn. Swamp isotome is perfect as an underplanting of roses and other shrubs or even perennials that tend to become bare at the base. Swamp isotome can also act as a lawn substitute in partially shaded or shady areas with fresh soil. Since it forms very dense mats, weeds are reliably suppressed. The blue star creeper can also be used in bowls and trays. Suitable plant partners are, for example, the earlier flowering silver lady’s mantle (Alchemilla hoppeana) and the primrose (Primula vulgaris), earleaf bellflower (Campanula cochleariifolia) and Cheddar pink (Dianthus gratianopolitanus), in shady places also small hostas and sedges.


There are different types of swamp isotome, such as the white ‘Alba’, the variety ‘Treadwellii’, whose white flowers show light blue stripes, or the deep blue ‘County Park’. They all bloom just as tirelessly from May to October, form dense mats and are just as winterproof.

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