How to propagate boston fern?

Boston Fern Propagation: How To Divide And Propagate Boston Fern Runners

The Boston fern (Nephrolepis exaltata ‘Bostoniensis’), often referred to as a sword fern derivative of all cultivars of N. exaltata, is a houseplant popularized during the Victorian era. It remains one of the quintessential symbols of this time period. The commercial production of the Boston fern began in 1914 and includes around 30 tropical species of Nephrolepis cultivated as potted or landscape ferns. Of all fern specimens, the Boston fern is one of the most recognizable.

Boston Fern Propagation

Propagating Boston ferns isn’t too difficult. Boston fern propagation may be accomplished via Boston fern shoots (also referred to as Boston fern runners) or by dividing Boston fern plants. Boston fern runners, or stolons, may be removed from a mature parent plant by taking the offset whose runners have formed roots where they come into contact with the soil. Thus, the Boston fern shoots create a new separate plant.

Historically, the early nurseries of central Florida grew stock Boston fern plants in beds of cypress-covered shade houses for the eventual harvest of the Boston fern runners from older plants to propagate new Boston ferns. Once harvested, these Boston fern shoots were wrapped in newspaper bare rooted or potted and shipped out to the Northern reaches of the market.

In this modern era, stock plants are still kept in climate and environmentally controlled nurseries wherein the Boston fern runners are taken (or more recently tissue cultured) for propagating of Boston fern plants.

Propagating Boston Ferns via Boston Fern Runners

When propagating Boston fern plants, simply remove the Boston fern runner from the base of the plant, either with a gentle tug or cut with a sharp knife. It isn’t necessary that the offset have roots as it will easily develop roots where it comes into contact with soil. The offset may be planted immediately if removed by hand; however, if the offset was cut from the parent plant, set it aside for a couple of days to allow the cut to dry and heal over.

Boston fern shoots should be planted in sterile potting soil in a container with a drainage hole. Plant the Boston fern shoot just deep enough to remain upright and water lightly. Cover the propagating Boston ferns with a clear plastic bag and place in bright indirect light in an environment of 60-70 F. (16-21 C.). When the offshoot begins to show new growth, remove the bag and continue to keep damp but not wet.

Dividing Boston Fern Plants

Propagation may also be achieved by dividing Boston fern plants. First, allow the fern roots to dry out a bit and then remove the Boston fern from its pot. Using a large serrated knife, slice the fern’s root ball in half, then quarters and finally into eighths.

Cut a 1- to 2-inch section and trim all but 1 ½ to 2 inches of roots, small enough to fit in a 4- or 5-inch clay pot. Put a piece of broken pot or a rock over the drainage hole and add some well-draining potting medium, covering the centered new ferns roots.

If the fronds look a bit sickly, they may be removed to reveal the young emergent Boston fern shoots and fiddleheads. Keep moist but not wet (set the pot atop some pebbles to absorb any standing water) and watch your new Boston fern baby take off.

Nephrolepis exaltata ‘Bostoniensis’ (Boston Fern)

Boston Fern Care Guide

Light

Reasonable light levels are needed. A Boston Fern will accept some full Sun and some quite shady areas, but for a happy and healthy looking plant you should aim for a fairly bright spot which does not receive harsh sunlight.

A North facing window would be ideal. East (or West in a pinch) would be acceptable, but South facing in full sunshine should be avoided.

Watering

All ferns are sensitive to watering routines and the Boston Fern is no different. The soil should be almost always moist in all seasons except for winter, during which you only need to water when the soil surface is dry. This means you could be easily watering this plant several times a week during hot weather.

Moisture is great, but do not over water a Boston Fern

Moisture is great, but do not over water to a point where the soil becomes sodden and completely saturated. Try where possible to use rain water, but if you can’t provide this, tap water is okay. Just make sure its been allowed to sit at room temperature for an hour because very cold water can shock the roots.

Humidity

Boston Ferns do need a high level of humidity to really thrive. They absolutely love moist air, will accept average levels, but will suffer if humidity is low. Avoid placing near radiators or hot air vents which dry out the air considerably.

This is the plant for the bathroom providing it has natural light and you can fit it in somewhere. Wherever it ends up, if practical mist the leaves regularly or check out some other ways to increase humidity.

Feeding

Feed using a general all purpose fertiliser at normal strength once every couple of months.

Temperature

Warm to average warmth during the day with a natural decrease in temperature at night will work wonders on the foliage, 16°C – 26°C / 60°F – 80°F. In any case, no lower than 10°C / 50°F.

Repotting

Only repot if you are happy for the plant to grow bigger and even then, only when the roots have filled the existing pot. Take extra care to keep the fern at the same soil level it sat at before. It’s really important not to bury the crown as this will lead to crown rot and the eventual death of your plant.

Propagation

Some owners like to try and propagate by growing the spores which a healthy and mature fern will produce. This is quite complex and time consuming, in addition some plants sold as “Boston Ferns” are not actually pure species and thus the plant wont produce viable spores anyway.

So it’s usually more productive to divide a large plant into 2 or 3 pieces when you repot, or a more reliable approach is to look out for “baby” ferns appearing on “runners” at the edges of the pot. After they are large enough to handle they can be cut away from the “runner” and potted up in a similar compost mix.

Speed of Growth

Expect rapid and regular growth for much of the year when conditions are favorable. Growth will slow in cooler temperatures or if the roots have no where left to grow.

Height / Spread

A max height of 90cm / 3ft and a spread of 180cm / 6ft after many (many) years.

Flowers

Almost all houseplants have flowers of some kind, even if quite rare. Ferns are the exception. No matter what you do you will never get the Boston Fern to bloom. Instead you may find it develops brown spots or “spores” on the underside of the fronds .

It’s really important you can recognise these as they are all too often mistaken for some sort of insect infestation, at which point the plant is either thrown away or its owner reaches for the insecticide and sprays the fern to death. It’s true they can look like Scale, but where as Scale will appear in a random pattern, spores appear in rough lines and in an easy to see pattern. (See photo right).

Is the Boston Fern Poisonous?

The Boston Fern is non-toxic to people, cats and dogs.

Anything else?

Due to the plants sensitive nature of chemicals (and because it’s too fiddly anyway) avoid leaf shine products. If you want to wash off any accumulated dust, run it under the shower for a few minutes.

Boston Fern Problems

Dark brown spots on the underside of the leaves

This is normal and shows you have a healthy plant!

Pests

Scale can be a problem and so can Red Spider Mite if the air around the plant is dry. You don’t want an infestation of Scale as they are especially hard to remove from a fern as the plant itself doesn’t take chemical pesticides well.

Therefore check the plant for these bugs every few weeks and remove the effected fronds completely or look at organic means of pest control. Red Spider Mite can be deterred by providing high levels of humidity (which the fern prefers anyway).

Brown leaves / fronds

In most cases this is a result of dry air, or allowing the soil to dry out too much before re watering. Annoyingly it can also be a indication you’re overwatering.

The soil should be moist for much of the time, so think back over what you have been doing and adjust to better meet the Boston Ferns requirements. Cut the brown off as the green won’t return.

Boston Fern Leaf Drop

Some leaf drop is normal. By “some” we literally mean the odd couple of leaves every week or so. If you’re getting more than that it’s likely a watering issue. Namely not enough.

I’ll be honest here. Our watering routine for our ferns is not the best. The soil does dry out completely from time to time and we get lots of leaf drop. Sometimes you can “rake” the fronds with your hands and end up with 20 or 30 leaves falling onto the floor! However our Boston is pretty old and pretty big. 30 leaves is nothing to our plant so there is no lasting damage or negative effects appearance wise.

These are forgiving plants and will recover easily providing you don’t leave it too long before noticing the roots are dry. Give it some water and after a few weeks new growth will take off.

Yellow leaves / fronds

Many possible causes. It could be from using hard cold water, exposure to draughts, chemicals or toxic smoke, i.e. from coal fires. Natural ageing also produces yellowing leaves. Study the care requirements detailed above and try to meet these requirements to keep the rest of the frond healthy and green.

About the Author

Tom Knight

Over the last 20 years Tom has successfully owned hundreds of houseplants and is always happy to share knowledge and lend his horticulture skills to those in need. He is the main content writer for the Ourhouseplants Team.

Also on Ourhouseplants.com

Credit for the Boston Fern in the Blue Bucket – Article / Gallery – bfishadow
Credit for the Boston Fern showing its leaf spores – Article / Gallery – David Eickhoff

How to Propagate a Boston Fern

About Boston Ferns

Ferns still have characteristics they developed millions of years ago and are often used to illustrate the concept of reproduction through spores. They do not flower or develop seeds. Spores have a distinct survival advantage, as they can remain viable for many years. To some extent, spores in Boston ferns are a back-up mechanism, as the plant can also reproduce from offsets.

Propagating with Spores

This takes time. Here’s how:

  • Cut a frond and fold in a sheet of paper; ripe spores will drop within 24 hours.
  • Dust spores over sterilized earthworm compost mix; cover with clear plastic.
  • Place under cool white fluorescent lights for 14 hours a day.
  • Mist green haze that appears after several weeks.
  • Two weeks later, transplant small clumps to pots and grow on.

Dividing the Plant

Like most perennials, Boston ferns can be propagated by dividing the original plant. Spread the leaves of your fern and you will see multiple crowns, similar to a clump of daisies or other perennial flowers. Remove the plant from its pot, divide in quarters or eighths with a sharp knife and replant the divisions.

Boston Fern Offsets

Boston ferns will begin to develop offsets if they are healthy and well-established. In the wild, these new plantlets would drop to the soil surrounding the mother plant and send down roots. In this way, the plant would gradually expand, with the healthiest new plants always on the outer perimeter and moving into fresh soil.

Propagating from Offsets

Offsets on a Boston fern look like miniature ferns hanging from a long rhizome, with two to four leaves and a root mass. Cut or pull the offset from the mother plant. Wrap the roots around your index finger and push the root coil into a small pot full of commercial potting soil. Don’t bury the crown. Place in indirect light and mist two to four times a day.

Growing On

New plants from spores, young transplants and divisions need a little pampering. Keep them out of direct sunlight, which can burn leaves. A windowsill or green house with bright indirect light and a shade to keep out full sunlight is ideal. Water to keep the soil moist, but don’t let it get soggy. Do not fertilize young Boston ferns, as they are easily burned by fertilizer.

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