Sweet-fern
Comptonia peregrina
also called sweetfern
Not a fern but a low aromatic shrub with fern-cut leaves that perfume the air around them on a warm day, thriving on roadside sand and gravel that starves everything else.
- Type
- Shrub · Perennial
- Botanical family
- Mixed / other
- Foliage color
- Green
- Sunlight
- Full sun to light shade
- Watering
- Low
- Soil
- Poor, acidic, dry sand or gravel; rich soil ruins it
- Feeding
- Gentle all-organic
- USDA zones
- 2b–6b
- Frost tolerant
- Yes
- Plant out
- at the last spring frost
- Plant spacing
- 3 ft 11 in
- In-row spacing
- 3 ft 3 in
- Between rows
- 4 ft 11 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
- 10–20 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.
A nitrogen fixer that spreads by rhizome across poor sandy ground, which is what it is for. It resents being moved once settled, so plant it small and let it go.
The habit is Sweet-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
- Leaves for tea and drying through summer; no other harvest and almost no other care.
- What to look for
- Full-grown leaves on a warm day, when the resinous smell carries.
- How to harvest
- Strip a few handfuls of leaves, dry them loose in a basket out of the sun. Crush a leaf on the way past regardless; that is the daily harvest.
- How often
- As wanted; the plant never misses what you take.
- Storing the crop
- Dried leaves keep a year and make a woodsy tea. The patch itself needs nothing but the poor dry ground you promised it.
- Generally trouble-free No notable pest or disease problems when grown in the right conditions — one of the easy ones.
Like a legume it fixes its own nitrogen through root bacteria, which is how it makes a living on subsoil and mine spoil. The dried leaves make a woodsy tea, and a handful crushed on the way past is the whole reason to plant it by the path.
The Cottage Garden Companion — the gardener's herbarium at cottagegardencompanion.com