Propagate Boston Fern – Divide or Pin a Runner

Propagate Boston Fern – Divide or Pin a Runner guide illustration

Divide Boston fern in spring, or pin a runner to a second pot while it is still attached.

How to Propagate Boston Fern care summary diagram

Divide in spring, or pin a runner while it is still attached

FactorRecommendedAvoid
WhenSpring, when new fronds start, or when the basket is packedDo not split a wilted plant in the dead of winter
DivideCut the root ball vertically so each piece has fronds and rootsDo not carve out a piece with no green fronds
RunnerPin the plantlet onto moist mix while it is still attached, then cut it free once rootedDo not snap the string off before it has roots in the new pot
MixFresh peat-based mix in a draining pot that just fits the divisionDo not drop a small piece into a huge pot of wet mix

Boston fern makes new plants from the root ball and from slender runners. Named kinds do not come true from spores, so divide or pin a runner instead of sowing the brown dots under the fronds. [1] [2]

When should I divide a Boston fern?

In spring, when new fronds start, or when the basket is packed. Late-winter splits work if growth is starting.

Can I root the long strings?

Yes. Those are runners. Pin a plantlet onto moist mix while it is still attached, then cut the string once it has rooted.

How to divide a Boston fern

Work when the plant is hydrated. Each piece needs roots and green fronds so it can recover.

  1. Water the day before so the root ball slides. Ease the plant out of the basket.
  2. Cut the ball in half, then into quarters if it is large, with a clean knife. Keep as many fronds as you can on each piece.
  3. Pot each piece in a draining pot that just fits. Set it at the same depth. Water in, and dump the saucer.
  4. Keep it in bright indirect light while it settles. Skip fertilizer until new fronds start.

How to pin a runner

Runners are the long, thin strings from the base. A small plantlet forms at the tip. Keep that plantlet attached to the parent until it roots. [3]

  1. Fill a small draining pot with moist peat-based mix, and set it next to the parent.
  2. Lay the plantlet on the mix and pin the runner so it stays in contact. Do not crush the stem.
  3. Keep the small pot moist. When a gentle tug meets resistance, cut the runner between the parent and the new plant.
  4. Grow the new plant as a small Boston fern. Care for the parent you already have on How to Grow Boston Fern.

Step up one pot size if you are not splitting

If you want one plant, not two, move it in spring to a pot only one size larger, or trim a few outer roots and return it to the same pot with fresh mix. Do not keep stepping it into an ever-larger container. [4]

  1. Water the day before. Ease the root ball out in one piece.
  2. Choose a pot about one inch wider, with a drain hole. Set the crown at the same depth.
  3. Fill around the sides with fresh peat-based mix. Water in, and dump the saucer.
  4. If the basket is packed with many crowns, split it instead of stuffing the whole clump into a much larger pot.

Can I just move it to a bigger pot?

You can step up one pot size in spring if you do not want more plants. A packed basket is usually split instead of stuffed into a much larger pot.

If you wanted a second plant, split the ball in spring — a frond cutting will not root.

FAQ

Can I grow it from a leaf cutting?

No. A frond without a piece of rhizome will not make a new plant. Divide the ball, or pin a runner.

Will spores make the same plant?

Not on named Boston fern. The brown dots under the fronds are sori. Divide or pin a runner if you want a matching plant.

Recommended plants

References

  1. [1] University of Wisconsin Horticulture - https://hort.extension.wisc.edu/articles/boston-fern-nephrolepis-exaltata-bostoniensis/
  2. [2] New York Botanical Garden - https://libanswers.nybg.org/faq/222598
  3. [3] NC State Extension - https://plants.ces.ncsu.edu/plants/nephrolepis-exaltata/
  4. [4] University of Arkansas Extension - https://www.uaex.uada.edu/yard-garden/resource-library/plant-week/boston-fern-11-18-05.aspx

This note is part of Nephrolepis Guides.

More notes on making another plant live in Propagating Guides.

Updated: Reviewed by Bosquelle Editors

This guide is written for real gardens, not perfect climates. Results vary with site, season, and plant choice. We draw on multiple sources and practical experience; treat the steps here as honest guidance, not a promise that every bed will behave the same.