Fan Maidenhair

About

Adiantum tenerum is a tropical maidenhair with arching fronds made up of many small, fan-shaped, fresh-green leaflets. Each leaflet sits on a fine, wiry, dark stalk, giving the plant a soft, lacy look. It grows larger than the small wall-crevice maidenhairs, but it is also more tender and needs more moisture.

Its background is the warm, humid forest of tropical America, in shaded, moist, sheltered pockets, so it needs steady warmth, high humidity and a root ball held evenly damp at all hours. Its main weakness, the one behind the alias brittle maidenhair, is that the delicate leaflets brown and fall within hours the moment the air goes dry or the compost is left to dry out.

Grown in a warm, humid, softly lit spot and never allowed to dry, it is a beautiful, lacy plant, though it needs more than the tougher southern maidenhair fern. A steamy bathroom, a terrarium or a grouped, humid corner suits it far better than a dry, draughty room. Give it warmth, damp air and steady moisture, and it grows into a soft green mound.

Appearance and character

The fronds arch and divide finely into many small, fan-shaped or wedge-shaped fresh-green leaflets, each on a fine, wiry, gleaming black-brown stalk.

The dark, hair-thin stalks and the delicate green fans give the plant its soft look and its common name, and the fronds stir at the least movement of air.

It grows from a tufted crown, arching outward, larger than the small hardy maidenhairs, and its new fronds open pale and coppery before they green and expand.

It reproduces by spores carried beneath the leaflet margins, and it is grown wholly for its lacy foliage, no maidenhair bearing a flower.

Where it is from

Adiantum tenerum grows in the warm, humid forests of tropical America, in shaded, moist, sheltered spots, often on banks and rocks near water. It is a plant of unbroken warmth and damp, not of open or dry ground.

That forest habitat explains its care. It needs steady warmth, high humidity and even moisture, under bright but filtered light. It cannot take frost, chill or a dry atmosphere, and its delicate leaflets brown and drop fast if the air dries or the root ball is allowed to parch.

How it grows

It grows across the warm months, unrolling fresh lacy fronds, and it needs warmth and humidity year round to keep them. Warm, damp, filtered conditions keep it healthy; a single dry spell or a cold draught can brown and shed the leaflets.

Root it in a loose, peat-free growing medium that drains freely yet holds its damp, in a pot matched to its roots, and keep that medium evenly damp at all hours with rainwater or filtered water. Never let it dry, even once.

Give it bright but filtered light, steady warmth over roughly 13 deg C, and high humidity from a humidifier, a pebble tray or grouped plants. Keep it well clear of radiators and cold draughts. If it browns badly, cut the fronds back and hold the warmth and damp, and it often shoots again.

Increase it by dividing the crown in spring, or from spores, which is slow.

Through the seasons

Spring starts fresh, lacy growth. Divide it if you want more, restart the feeding, and hold it evenly damp and humid.

Summer is the main growth period. Keep the medium evenly damp, the air humid, feed monthly, and keep the fronds off any direct sun.

Autumn slows growth as the light fades. Cut the feed back but keep the warmth and humidity up against the drying effect of heating.

Winter rests the fern. Keep it over about 13 deg C, evenly damp and humid, well clear of cold draughts and dry heat.

Care difficulty

Moderate to demanding, entirely because it must never dry and needs unbroken warmth and humidity. Given those, it is a lush, lacy plant. It declines quickly if the air goes dry, the compost parches, or a cold draught reaches it, when the delicate leaflets brown and fall. It is a fern for a warm, humid spot such as a bathroom or a terrarium instead of an ordinary dry room.

Watering

Keep the medium evenly damp at all hours, never letting it dry even once, since a single dry spell browns and drops the leaflets. Water with rainwater or filtered water, as it dislikes the salts and fluoride of hard tap water.

Never leave it waterlogged either, since the roots rot in a sodden, airless medium; the aim is steady, even damp. It needs slightly less water in winter but must still never dry.

Warning signs, diseases and pests

Browning, dropping leaflets are the common problem and mean the air is too dry, the compost parched, or a cold draught reached it. Restore warmth, humidity and even damp, and cut back badly browned fronds to encourage fresh ones.

Warm, dry air also brings on spider mites, which stipple the delicate fronds; raise the humidity and treat early. Scale insects may settle on the wiry stems and be wiped off.

A plant that has browned badly is often not dead. Cut it back, hold it warm, humid and evenly damp, and it usually shoots again from the crown.

Growing environment

Bright but filtered light suits it, matching its shaded forest habitat. Direct sun scorches the delicate fronds, and deep shade thins them. A bright spot out of the sun is ideal.

Warmth and humidity are essential. Keep it over about 13 deg C and raise the humidity with a humidifier, a pebble tray or grouped plants, well clear of radiators and cold draughts.

Grow it in a loose, moisture-holding, peat-free growing medium, standing it in a warm, humid, softly lit spot such as a bathroom or a terrarium.

Feeding

Feed monthly across the growing season with a weak, balanced liquid. It is a light feeder and dislikes strong fertiliser, which can scorch the delicate fronds.

Ease off through autumn and feed little over winter. An occasional flush of plain water clears the salts to which it is sensitive.

Troubleshooting

The leaflets are browning and dropping. The air is too dry, the compost parched, or a cold draught reached it. Restore warmth, humidity and even damp, and cut back badly browned fronds to encourage fresh ones.

It dried out and looks dead. It often is not. Cut the browned fronds back, hold it warm, humid and evenly damp, and it usually shoots again from the crown.

Why is it fussier than my other maidenhair? This is a tender tropical species that must never dry and needs unbroken warmth and humidity, where the southern maidenhair fern is a touch tougher. Both dislike dry air.

The fronds look dull and speckled. Spider mites, from warm, dry air. Raise the humidity and treat early.

Is it safe around pets? Yes. No maidenhair is listed as toxic, so it is safe alongside cats, dogs and children.