Blehnum, or Derbyanka – capricious fern care

Blehnums, or Derbyanki – ferns in culture are quite capricious. They do not tolerate cold or drafts. They need high humidity and at the same time do not respond well to spraying. It is best to grow Blehnums on a “tropical window”. The leaves are a bit like the “cap” of palm leaves. In older specimens, the trunk is clearly visible at the base. Read about the features of growing this fern in our article.

Blechnum humb, or Derbyanka hump (Blechnum gibbum). Farmer plantsrescue


Derbyanka is a botanical description

Derbyanka clan, or Blehnum (Blechnum) has about 140 species of ferns of the Derbyankov family (Blechnaceae), distributed mostly in tropical and subtropical regions. Under natural conditions, one species of Derbyanka grows in Russia – Spikelet Derbyanka, or Spiked Blehnum (Blechnum spicant).

In nature, Derbyanka is a large, palm-like plant with branches reaching 1 m in length. The stem of the fern is a modified rhizome; in old plants in indoor conditions it reaches a height of about 50 cm, covered with brown scales. Its branches are once pinnately dissected, about 50-60 cm long, light green in color. Sporangia on the underside of the leaf, closer to the edge of the segments.

Types of Blehnum

In indoor conditions, the following types of Derbyanka are most often grown:

  • Blehnum humpbacked, or Derbyanka humpback (Blechnum humps). Differs in bright green leaves with little or no petioles. The most popular type in indoor floriculture.
  • Blehnum brazilian, or Derbyanka Brazilian (Blechnum brasilense). It has wide leaves of olive green color.
  • Blehnum Moore, or Derbyanka Mura (Blechnum moorei). A small shrub about 30 cm in size, the leaf petioles are almost black, while the leaves themselves are dark green and shiny.
  • Blehnum serrated, or Derbyanka serrated (Blechnum serrulatum), synonym – Indian Blehnum, Indian Derbyanka (indigo Blechnum).

Requirements for growing Blehnum

Lighting: the place must be necessarily shaded from direct sunlight – i.e. diffused light or light partial shade. Blehnum is a shade-tolerant plant, it is recommended to place it on the north or west windows, as well as in the back of the room. Direct sunlight can harm the plant.

Watering: only with warm, settled water that does not contain lime. Watering in spring and summer is abundant, in winter it is moderate, but the soil should be moist all the time. For blehnum, both drying out and excessive soil moisture are equally harmful. It is advisable not to water the young plant from above, but to lower it into the water together with the pot, leaving it for 1-2 minutes. After that, the excess water must be allowed to drain.

Air humidity: Like many ferns, Blehnum loves humid air, but spraying can ruin the leaves. Therefore, pots with plants are placed on pallets with wet expanded clay. The batteries are covered with a damp cloth in winter.

Transfer: transplant is carried out in the spring, when the roots fill the entire pot. The soil should have a slightly acidic reaction. Blehnum is planted in a soil substrate suitable for most ferns. Typically, it consists of 2 parts of peat soil, 2 parts of humus, 1 part of chopped moss and 1 part of sand. Transplant the plant as it grows, when it becomes cramped in the pot. The fern should be watered two days before transplanting.

Additional fertilizing: in summer, liquid fertilizer for indoor ornamental deciduous plants every two weeks. Blehnum is very sensitive to excess fertilizers, so the dose should be taken 2 times less than the manufacturer’s recommended dose. Winter-autumn – no feeding.

Undercut: does not need.

Temperature: the most optimal for growing ferns – 18-22 ° C. High temperatures can cause the plant to get heat burns. Blehnum must be protected from drafts.

Blechnum Mura, or Derbyanka Mura (Blechnum moorei)
Blechnum Mura, or Derbyanka Mura (Blechnum moorei). Farmer Stan Shebs

Reproduction Blehnum

Derbyanki are propagated by spores and division of rhizomes. When transplanting, the rhizomes are divided into parts with a sharp knife, the cuts are sprinkled with crushed charcoal, each part is planted in a separate pot. You should pay attention to the number of growth points. If there is only one growth point or they are few in number, then it is impossible to divide the plant, this can lead to death. Young plants do not start growing immediately after division.

You can try to propagate the plant from the spores that form on the underside of the leaves. They are sown in early spring, best of all in a nursery, heated from below, where a temperature of 21 ° C is maintained. Cut off a leaf from the plant and scrape the spores onto paper. Fill the nursery with a layer of drainage and decontaminated soil for sowing seeds. Water the soil well and scatter spores as evenly as possible. Cover the nursery with glass and place in a dark, warm place.

Remove the glass briefly each day to ventilate, but do not let the ground dry out. The nursery should be kept in the dark until the plants appear (this will happen in 4-12 weeks). Then transfer it to a lighted place and remove the glass. When the plants grow, thin them out, leaving the strongest at a distance of 2,5 cm from each other. Young specimens that develop well after thinning can be transplanted into pots with peat soil – 2-3 plants together.

Blechnum humb, or Derbyanka hump (Blechnum gibbum)
Blechnum humb, or Derbyanka hump (Blechnum gibbum). Farmer Forest & Kim Starr

Diseases of the Derbyanka, or Blehnum

Leaves turn yellow, brown spots appear on them – it means that the temperature in the room is too high (above 25 ° C), which is not desirable for ferns. Irregular or insufficient watering and frequent spraying may also be the reason.

Leaves turn yellow, the plant grows poorly – too low humidity in the room, proximity to the heating system, similar symptoms can be observed if the plant is planted in very heavy soil or too large a pot.

Leaves are faded, translucent, lethargic – too intense sunlight.

Leaves are pale or dull, the ends turn yellow or brown, the plant does not grow or grows poorly – lack of nutrition, too small or too large a pot.

Leaves can turn yellow, turn brown, curl and fall off, young leaves wither and die – when the room temperature is too low, from exposure to cold drafts, watering with cold water, when watering with hard or chlorinated water.

Blechnum spicant, or Derbyanka spikant (Blechnum spicant)
Blechnum spicant, or Derbyanka spicant (Blechnum spicant). Farmer Tigerente

Nobody says that fern is easy to grow, but that’s the whole interest, the main thing is to get it. Although moody, the result is worth it!


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Anna Evans

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