Blechnum penna-marina

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The alpine water fern forms a dense groundcover and features coppery-red new growth.

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December 7, 2018
Mark Leichty
Blechnum penna-marina growing in a rock wall at Bloedel Reserve, Bainbridge Island, Wash.
Photos by Mark Leichty

I began writing this column in January of this year, and led off with an extraordinary fern, Asplenium trichomanes, or maidenhair spleenwort. It seems like a fitting act of completion to end the year with another of my favorite ferns, Blechnum penna-marina, or alpine water fern. The common name is a bit misleading, as the fern does not grow in water at all and is in fact somewhat drought tolerant. The name water fern was bestowed anecdotally by pteridologists who noted that it thrives near waterways. It is a native of the Southern Hemisphere, with indigenous populations in Chile and Argentina, New Zealand, Tasmania and Australia.

I’m a fan of this fern for several reasons. First, its coppery-red new growth each spring is striking, with the fronds fading to a rich green as the summer progresses. The red colors are richer if the plant is in a sunnier location and it will grow in full sun with plentiful summer water. Ideally, it would be placed in light shade with acidic soil that is well-drained with moderate summer water. Now comes the good part. Blechnum penna-marina is a groundcover fern, reaching a height of 10 inches or less. It spreads slowly via creeping rhizomes and forms a dense mat that suppresses weed growth. A single plant can cover a diameter of 5 feet. It grows more compactly in higher sun conditions.

Blechnum penna-marina is an exceptional container plant as well. It’s useful as a front-tier plant in a large container, perhaps accompanied by Asplenium trichomanes, black mondo grass, or even larger Sempervivums such as ‘Carmen’ or ‘Black.’

 

Why grow Blechnum penna-marina?

  • It forms a dense groundcover that does well in a wide variety of exposures.
  • It’s deer and slug resistant.
  • It has beautiful coppery-red new growth.
  • Being a groundcover, customers usually buy multiple plants, therefore increasing sales.