Blechnum penna-marina

Low-growing, compact, evergreen fern from 5 to 25 cm in height, depending on conditions.

Dark green fronds can grow to 20cm long and 2cm wide. Young fronds are tinged red. Fronds are spread via rhizomes to form clumps.

Prefers moist, humus-rich soil in a sheltered site. However, it is quite hardy and can be grown in a wide variety of situations. Best results are achieved if the soil is slightly acidic and contains plenty of decomposed organic matter.

Surprisingly ferns are not that fussy about soil as long as the small roots (rhizoids) are able to spread through an organic layer with most species preferring good drainage. Watering is usually necessary during dry summer months and a good mulch will help keep moisture around the roots.

Always choose healthy well-grown plants and plant after autumn rains. Before planting ensure the root ball is saturated and remove the planter bag or pot with minimal root disturbance. Trim any broken roots and plant at the same level as in the container. Dig a hole twice the diameter of the root ball and firm in and water once planted. Make sure the plants are watered well until established if planting in a drier period. Plant with some general slow release fertiliser and then every spring apply an organic based fertiliser such as blood and bone at a handful per square metre as new growth begins. Plant approximately 50cm apart. Containers can be planted at any time of the year as they require frequent watering.

Requires well-drained soil with plenty of organic matter. Mulching helps conserve moisture and suppress weeds. Organic materials, such as sawdust and bark, contribute to soil structure as they decompose. Keep mulch away from plant stems.

The root ball sometimes dries out despite the surrounding soil being moist. When this occurs, directly water down the plant stem to saturate the root ball. The first summer and autumn after planting are critical for young plants, so water thoroughly during dry periods. When grown in full sun and exposed conditions, the fronds can become windburnt.

Requires no major maintenance. Remove old fronds when they become unsightly. Benefits from regular applications of fertiliser.

No pest and disease issues.

Native Identification Trail

Blechnum penna-marina is a native alpine water fern that can survive temperatures as low as -25 C.

Its natural range covers the North and South island, as well as Stewart, Chatham, Antipodes, Macquarie and Auckland Campbell Islands. It is present on Mt Taranaki. It also grows in Australia, some Pacific islands and in South America. This species' habitat is coastal to alpine, in open forest, subalpine scrub, grassland, alpine herb fields, and in moss fields on shaded rock outcrops. Frond length decreases with altitude to a few centimetres near the upper limit of its range.