Repotting guide

When & how to repot American Cranberry (Vaccinium macrocarpon)

Also called large cranberry, American cranberry.

More about american cranberry

About American Cranberry

Vaccinium macrocarpon · also called large cranberry, American cranberry · edible

American cranberry is a low, creeping, evergreen bog plant grown commercially for its tart red berries used in juice and sauce. It needs permanently moist, strongly acidic, sandy peat and full sun. Wiry trailing runners root as they spread, while short upright shoots carry the pink flowers and fruit through autumn harvest.

Mature size: 10-20 cm tall, with runners spreading 60-90 cm or more.

Watch for — Drying out: As a bog plant it cannot tolerate dry soil even briefly; runners and fruit shrivel fast. Keep the root zone permanently moist, standing pots in water during summer.

How to tell american cranberry needs repotting

Repotting on a calendar is less reliable than reading the plant. For american cranberry, watch for these signs:

Roots circling the bottom of the module or pot, or poking out of the drainage holes.
The seedling dries out within a day and growth has visibly stalled.
Roots are white and matted in a tight spiral when you tip the plant out.
It has outgrown its current container for the stage of the season — pot american cranberry on before it becomes hard root-bound.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot american cranberry

Pot on seedlings as they grow; not a perennial repot. American Cranberryis grown for one season, so the question is really “how often to pot on” — keep moving it up before the roots circle. Trailing, mat-forming evergreen groundcover; long horizontal runners root and spread, with short vertical fruiting uprights rising from them..

What size pot to step american cranberry up to

Pot american cranberry on gradually — a seedling jumped straight into a huge pot sits in cold, wet, airless soil and stalls. Step up one or two sizes at a time as the roots fill each container, finishing in a large final pot or the ground. The aim is roots that never circle and never check.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot american cranberry

Pot american cranberry on through the active growing season, whenever roots fill the current container — there is no single date, just "before it becomes root-bound". Avoid potting on during a cold snap.

Step-by-step: repotting american cranberry

Pot on before it is root-bound. Check american cranberry regularly; move it up as soon as roots reach the edge of the cell or pot, not after they have circled.
Step up one or two sizes. Choose the next container up — not a giant one. Cold, wet, unused soil around a small root system stalls seedlings.
Knock it out gently. Support the stem, tip the pot, and ease the rootball out without breaking it. A little teasing of circled roots at the base is fine.
Pot into rich mix. Set it into fresh strongly acidic, sandy peat, moisture-retentive at the same depth (tomatoes are the exception — they can go deeper to root along the stem).
Water in and grow on. Water well, keep it in good light, and resume feeding once it is established and growing again.

Aftercare

Water american cranberry in well and keep it in bright light; a freshly potted-on seedling can wilt for a day while roots settle, so do not overcompensate by drowning it. Do not fertilise for about 1 week — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for american cranberry

American Cranberry wants strongly acidic, sandy peat, moisture-retentive. Requires pH 4.0-5.5. Grow in a sand-and-peat ericaceous mix that stays wet; ideal for bog gardens, lined beds and trays. Sharp drainage is not wanted here. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting american cranberry — frequently asked questions

How often should you repot american cranberry?

Pot on seedlings as they grow; not a perennial repot for american cranberry. American Cranberry is a seasonal crop, so you pot it on as a growing plant rather than repotting a perennial. Step seedlings up gradually into strongly acidic, sandy peat, moisture-retentive so the roots never circle the cell, ending in a large final container. A root-bound transplant stalls and never fully recovers.

What size pot does american cranberry need?

When is the best time of year to repot american cranberry?

Can you put american cranberry straight into a much bigger pot?

No. Even a fast-growing american cranberry should only go up one pot size at a time. A vastly oversized pot holds a reservoir of wet soil the roots cannot reach, which stays cold and soggy and rots the roots — the opposite of what you wanted.

Should you fertilise american cranberry after repotting?

Not immediately. Wait about 1 week after repotting american cranberry. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.