Sensitive fern
Onoclea sensibilis
Broad, un-ferny, almost tropical pale-green fronds that spread into a knee-high ground cover for wet shade, with beaded fertile spikes that stand all winter like bronze rattles.
- Type
- Flower · Perennial
- Botanical family
- Mixed / other
- Foliage color
- Green
- Sunlight
- Shade to sun if the ground stays wet
- Watering
- High
- Soil
- Moist to wet, any texture; happiest in muck
- Feeding
- Gentle all-organic
- USDA zones
- 4a–8b
- Frost tolerant
- Yes
- Plant out
- at the last spring frost
- Plant spacing
- 23.6 in
- In-row spacing
- 17.7 in
- Between rows
- 2 ft 6 in
- Square-foot density
- Not suited to SFG
- Root system
- Running rhizomes
- Working depth
- 4–12 in
- Can reach
- 18 in down where the soil allows
- Spread
- 6–12 ft across, about 2–4× the width of the plant
- Shallowest pot
- 12 in of soil
It travels underground, and it does not stop where you would like it to. Taking the tops off does nothing at all to the run, and every fragment left behind is a new plant. In open ground the only boundary that holds is a barrier sunk two spits deep, or a container with its rim standing clear of the soil.
The habit is Sensitive fern’s own; the figures are what that habit usually comes to at this size, not a measurement of this species. Roots follow the soil either way: a compacted pan, a high water table or heavy clay stops them well short of any of it, and deep open ground lets them go further.
- When
- Beaded fertile fronds for dried arrangements, cut any time from fall to late winter.
- What to look for
- The fertile spikes hard, dark and fully beaded; the green fronds will have gone with the first frost.
- How to harvest
- Cut the bronze bead-sticks at the base; they are already dry and ready to arrange. Pull the rhizome back where it has run past its welcome — it comes up easily in soft wet ground.
- How often
- One cutting; edge patrol once a season.
- Storing the crop
- The beaded fronds keep for years in a dry vase, shedding spores once indoors (shake them outside first).
- Generally trouble-free No notable pest or disease problems when grown in the right conditions — one of the easy ones.
The "sensitive" is to frost: the first touch in fall drops every green frond overnight. The beaded fertile fronds are cut for winter arrangements, and the plant colonizes ground too wet to walk on, which is exactly where to use it.
The Cottage Garden Companion — the gardener's herbarium at cottagegardencompanion.com