Caring for Indoor Ferns

Mistakes in care; pests and diseases

First aid for your ferns

Compared to other groups of plants, ferns are rarely infested with pests. Far more often they are the victims of mistakes in care because their species-determined requirements have not been met. However, should unwelcome visitors appear, you will find some useful advice here.


Common mistakes in care

Withering fronds may signal a whole range of problems but are usually caused by too little or too much watering. Fading young fronds, as a rule, indicate lack of water. Once you notice this, you should water immediately. The best thing to do in such cases is to immerse the whole plant in water.

ferns make an attractive feature for any homeOn the other hand, if you give too much water this will result in water-logging and the entire plant will wither. If all the air spaces in the compost around the roots are filled with water, no oxygen will be available to the roots, which they need in order to absorb water and nutrients. In spite of a plentiful supply of water, the plant will die of thirst. A fern that is withering because of persistent water-logging cannot be saved. The only thing left to try is to take the plant out of its pot-holder so that excess water can run away. Do not water again until the compost is slightly dry and then water sparingly in the future.

Dried up fronds are an indication that the rootstock of the fern has dried out. As long as this state of affairs is fairly recent, you can try to encourage the plant to produce new shoots by Immersing the rootstock in water.

Pale green fronds: The adult fronds of some fern species do not actually wither but will lose their fresh green colour and turn pale green. Finally, the feathery divisions of the frond fall off. These symptoms may indicate too much or too little water as well as a position that is too dark or too cool, particularly in the case of Nephrolepis. Check the rootstock with your finger to make sure the moisture content is correct and choose a position with enough warmth and light but out of direct sunlight.

Veins that turn brown and show up like lots of little lines on the feathery leaves of maidenhair fern (Adiantum) point to a position that is too cool and has high humidity. Place the maidenhair fern in a warmer position.

Brown edges to leaves are usually the result of humidity that is too low. In the case of Asplenium they may also be the result of a position that is too cool. Raise the humidity level and move the plant to a position that is sufficiently warm.

Dark brown, decaying parts of the leaves occur in Platycerium and Blechnum if they are misted and do not then dry off in a short space of time. These species do better if they are not misted all over but are supplied with indirect humidity.


Fungi and bacteria

Harmful fungi do attack ferns, particularly those that propagate by means of spores. The most frequent problem is grey mould which covers the sown spores with what looks like greyish-white fur. This leads to decay of the prothalli and young plants. The best remedy is good hygiene, as described in the chapter on propagation, Fungi or bacteria rarely occur on adult plants indoors. They are encouraged, however, by placing plants too close together, if they are too wet or if they do not have adequate ventilation.

Depending on the fungus species, infestation manifests itself through different symptoms. Grey mould forms a thick, grey white film which causes individual parts of the plant to decay and finally leads to the death of the entire plant. Other fungi cause irregular, grey to reddish-brown patches or growths on the leaves. In the case of Asplenium nidus bacteria may cause small, glassy spots to appear on the upper parts of the fronds, which may then spread rapidly in unfavourable circumstances.

In all diseases caused by fungi and bacteria, the infested fronds should be removed, you should refrain from wetting the plant and should offer a different position and less humidity. Combating the problem with synthetic agents (fungicides) is not usually worth the effort.

Animal pests

Among the few pests that occur on ferns it is gnats (Diptera, Sciaridae), scale insects and spider mites that are met with most frequently.

Occasionally you may also discover aphids, thrips, snails and slugs and leaf blotch eelworm.

If a plant is infested with harmful organisms, you can try various remedies.

Mechanical means are time consuming but very effective and entirely non-toxic. They can be used for aphids, Diptera, Sciaridae and slugs and snails.

• Scale insects can be scraped off with a knife.

• Aphids can be washed off with water.

• In the case of Diptera and Sciaridae, it is usually sufficient to catch the adult insects and prevent them from laying more eggs. This job is successfully carried out by using sticky yellow tags (available in the gardening trade) which can be hung up near the plants. The small gnats are attracted by the yellow colour and then get caught on the sticky surface of the yellow tags. You should also make sure that no stagnant moisture is allowed to lie around.

• Slugs and snails can be gathered up and removed.

Biological control, by means of useful insects, can be tried in the case of an infestation with aphids, spider mites or thrips. Useful insects like ladybirds, lacewings, gall midges and predatory mites will prey on pests. Others, like ichneumon flies, lay their eggs in the larvae of the pests and, on hatching, the ichneumon larvae consume their hosts.

Washes, teas or fermented brews are plant-based, pest-regulating agents that can be prepared at home. They are employed against aphids and spider mites as well as against fungal infections. The addition of an agent like washing up liquid, which will break the surface tension of water, will help the brew to stick to plant surfaces.

Chemical plant protection agents: Among the plant protection agents obtainable in the trade are insecticides and acaricides for use against pests. If at all possible, it is far better to leave these agents alone. It is true that they are broken down in the compost after a certain amount of time, but new compounds are created during this process and the effects of these have not yet been established. In addition, if these agents are used several times, strains of pests may develop that are immune to the effects of the agents.


Handling plant protection agents

• Seek advice from experts in the trade when buying chemical plant protection agents.

• Protect your environment by not using sprays containing CFC propellant gases.

• Always follow the instructions and advice on dosage given on the packaging meticulously.

• Before preparing any spray, work out the amount you will require so that all of the liquid is used up.

• Only spray outside.

• Do not spray on windy days and avoid allowing a spray cloud to drift into a neighbour’s garden.

• Wear gloves and do not breathe in the mist.

• When spraying, make sure you spray as evenly as possible and wet the undersides of leaves thoroughly.

• Carry out the recommended number of treatments at the intervals prescribed by the manufacturer in order to eliminate successive generations of pests.

• Store plant protection agents in their original packaging out of reach of children and domestic pets and make sure they are locked away.


The employment of chemical plant protection agents and mineral oils is particularly undesirable for ferns as these plants are very sensitive to many agents, particularly plants with young fronds. Always test any such spray treatment on a few leaves first. A preferable alternative is to use agents that do not harm useful insects. In the past plant protection agents containing pyrethrum, an extract from a species of chrysanthemum, or synthetic related substances (pyrethroids) were considered to be without risk for humans or nature. You should, however, be very careful with these agents as they have been suspected of creating allergies, having mutagenic properties, causing cancer and having other harmful effects. The direct penetration of pyrethrum into the bloodstream, for example through a cut, is considered to be particularly dangerous.

01. June 2011 by Dave Pinkney
Categories: House Plants, Indoor Ferns, Pests and Diseases, Plant Care | Tags: | Comments Off on Caring for Indoor Ferns


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