Blechnum: Growing Ribbed Ferns Indoors

A close-up of blechnum spicant
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The Blechnum genus is not particularly common as houseplants, which is a shame because there are some beautiful species of fern in this group. Blechnum are mostly native to medium-altitude tropical areas, where they grow in conditions that would be familiar to any fern grower: humid, cool but not cold, diffuse light. Given the right conditions indoors, they can be lovely ferns that will round out a collection of ferns.

Although their foliage is not particularly unique—somewhat resembling a cross between a tree fern and a cycad—the most common species in cultivation does have one lovely characteristic: the new fiddleheads on the red form are red when they emerge, gradually fading to green as they mature. Colorful foliage is relatively rare among ferns, making this an interesting characteristic. Overall, however, these are not particularly difficult ferns to grow, and if you have success with some of the more common species of ferns, you can likely grow these dependable and interesting ferns.

Growing Conditions

  • Light: Like many ferns, they prefer partial shade or dappled sunlight at the very most. They dislike direct sunlight and will strenuously object. It is possible to acclimate your fern to a greater amount of light, but only by providing proportionally greater amounts of water and humidity.
  • Water: Blechnum ferns prefer regular water throughout the growing season. These are fairly cold hardy as far as ferns go, so do not relish any prolonged dry period. It's also very important to provide high humidity, whether through a mister, humidifier or by setting the pot in a tray full of damp pebbles.
  • Fertilizer: Blechnum is not typically high consumers of fertilizer. However, they do appreciate a dose of a good controlled-release fertilizer at the beginning of the growing season.
  • Soil: Preferably a rich, humusy potting mix. They do not like mucky conditions, however, so be careful of soil that has compacted into a solid ball.

    Propagation

    Blechnum can be propagated through spores, using bottom heating to increase their germination. The most common species, B. brasiliense, is a short, single-stemmed plant that does not clump, so it won't be possible to propagate through division. In general, only serious hobbyists go the spore propagation method.

    Repotting

    Repot younger plants at the beginning of the growing season, stepping up the pot size slowly over the years. Mature plants can reach a height of 6 feet on a short trunk, resembling a primitive tree fern. The more attention you pay to proper potting, the larger and healthier your plant is likely to become.

    Varieties

    Blechnum deserve wider recognition in general, but a few species, in particular, are noteworthy:

    • B. brasiliense. Native to South America, this is the most popular species seen in cultivation. This plant looks like a tree fern when mature, and the red form sends up curled and red fiddleheads that mature to green. The trunk can reach three feet tall in mature plants, with tall fronds arching up from the stem.
    • B. gibbum. This plant can handle somewhat warmer temperatures than other Blechnum species. It grows on a tall, slim stem with stiff, nearly straight fronds. It's somewhat smaller than its cousin, B. brasiliense.

      Grower's Tips

      Immature Blechnum species look more like typical ferns, but as they grow and begin to form their typical trunk, they start to distinguish themselves. They resemble tree ferns but are considerably easier to grow and much smaller, so if you want a tree fern but don't have room, a Blechnum is a good option. If you like in a humid area, consider moving your plant to a patio or balcony in the summer. It will appreciate the outdoor growing season. If your plant begins to look brown along the leaf margins, it's likely suffering from lack of humidity. Try to increase the humidity. When kept too dry, Blechnum is vulnerable to mealybugs and aphids.