General
American cranberry is a low, evergreen, vine-like shrub forming runners that root and produce vertical ‘uprights’ bearing flowers and fruit. It thrives in cool climates with acidic, organic soils that stay evenly moist. Unlike commercial flooded bog production, home gardens should grow cranberries in raised, contained, acid beds or large planters. Aim for pH 4.0–5.5, high organic matter (peat/sphagnum + sharp sand), and consistent moisture with good aeration. Contain the bed to keep acidity, and mulch with pine needles or coarse peat to suppress weeds and conserve moisture. Plants spread 1–2 m but stay only 10–20 cm tall. Flowers in early summer; berries ripen deep red in autumn and store or freeze well.
Light
Full sun to light partial shade; 6–8 hours of sun gives best fruiting.
Soil type
Moist, acidic, organic-rich medium (peat/sphagnum with sand), well-drained yet evenly wet; avoid lime and high-carbonate water.
Water requirement
High. Keep consistently moist, never waterlogged in winter freeze. Use rainwater if possible.
Nutrient requirement
Low. Light feeding only; excessive nitrogen causes rank runners and poor fruiting.
Precultivation
- Seeds: Stratify cold and moist for 8–12 weeks (refrigerator, barely moist sphagnum), then sow on the surface under bright light at 18–22°C. Germination usually 2–5 weeks. Grow on cool and bright; pot up into acidic mix.
- Cutings/divisions: Preferred. Take 7–10 cm runner cuttings in late spring–summer, remove lower leaves, insert into acid medium (2:1 sphagnum peat:sharp sand) with high humidity. Root in 3–6 weeks. Overwinter young plants frost-free their first year if poorly rooted.
Planting
Plant when soil temperatures are above 5°C and risk of deep frost has passed. Prepare a 20–30 cm deep raised bed or large container lined (optional) with plastic/pond liner pierced for drainage; fill with 60–80% peat or milled sphagnum and 20–40% sharp sand. Target pH 4.0–5.0. Space plants 30–45 cm apart; 3–5 plants/m² for faster coverage. Water thoroughly with rainwater, then mulch 3–5 cm with pine needles or coarse peat. Install edging to prevent surrounding alkaline soil or lime leaching into the bed.
Pruning
Cranberries benefit from light, regular pruning. In late winter/early spring, thin a portion of old, woody uprights and shorten overly long runners to direct energy into fruiting wood. In midsummer, pinch vigorous new runners to encourage upright formation. Every 3–5 years, rejuvenate by removing a third of the oldest uprights.
Maintenance
Keep evenly moist; never allow to dry out. Use rainwater to avoid raising pH. Mulch annually with pine needles to suppress weeds and retain acidity. Fertilize sparingly in spring with an acid-forming, low-N feed (e.g., half-strength rhododendron fertilizer). Avoid manures and ashes. Protect flowers from late frosts with fleece. Net against birds if pecking occurs. Monitor for tip blight or fruit rots in wet summers; improve airflow and remove affected material. Iron chelate may help if leaves yellow from high pH.
Harvest
Harvest when berries are fully colored, firm, and bounce slightly—typically mid-September to late October. Pick by hand; no flooding needed. Store fresh at 3–5°C for 3–6 weeks or freeze whole. Best flavor develops after the first light frost. Use for sauces, baking, and dried fruit.
Common issues
- Yellowing leaves: Often high pH or hard irrigation water; switch to rainwater and add acidic mulch.
- Excessive runners, little fruit: Too much nitrogen or deep shade; reduce feeding, increase sun, summer pinch runners.
- Drought stress: Wilting and berry drop; increase watering and mulch.
- Frosted blossoms: Cover during late spring cold snaps.
- Fungal rots (fruit rot, tip blight): Improve drainage and airflow; remove infected parts; avoid overhead watering late in the day.
Pollination
Self-fertile, but cross-pollination by bumblebees/honeybees increases yield and berry size.
Companion plants
Blueberry (Vaccinium corymbosum), lingonberry/cowberry (Vaccinium vitis-idaea), bog rosemary (Andromeda), heathers (Erica/Calluna), dwarf conifers that prefer acidic soils.
Incompatible plants
Lime-loving plants (lavender, thyme, many vegetables), brassicas in limed beds, plants requiring high phosphorus or alkaline fertilizers.
