Shrub · Ericaceae
Cranberry
Vaccinium macrocarpon
Give it acidic peat, full sun, and steady moisture, and this low creeping vine pays out tart red berries through fall.
Full sun
Every 2–4 days
USDA 3–7
4–8 in · 10–20 cm
Overview
Picture a low evergreen vine pressed flat to the ground, its thin wiry stems trailing across the surface and striking root as they travel. This is the cranberry, native to the cool bogs and wetlands of northern North America, a member of the heath family alongside blueberries and lingonberries. Its small, leathery leaves stay green year round, and like its cousins it lives for very acidic, peaty ground that would starve most garden plants. The vines mound only a few inches tall while spreading wide.
Look closely and the plant's habit gives it away: a dense weave of creeping runners studded, in late spring, with delicate pink and white flowers, followed by the familiar red berries that color up through fall. It is also a fussy thing. The bed must stay evenly moist yet drained, the soil must sit near pH 4.0 to 5.5, and the plant wants full sun to set fruit well. Hardy and long-lived once it takes hold, it tests your patience before it pays you back.
This is a plant for a dedicated corner, not a mixed border. Give it a contained bog bed or a wet, acidic patch where the trailing runners can roam and mat out, keep the lawn and vegetables well clear, and a cranberry planting can keep throwing red fruit for decades.
Care
The short version: full sun, steady even moisture, and acidic peaty soil around pH 4.0 to 5.5. Keep fertility low, leave the creeping runners room to mat out, and rake the surplus away in early spring.
Light
Cranberries set the most fruit in full sun, with 6 or more hours a day landing on the bed. They will hang on in partial shade, but a shaded planting runs to leafy trailing runners and gives back only a scatter of berries.
Water
Hold the bed in constant, even moisture, watering roughly every 2 to 4 days so the peat never dries out. Drainage has to keep pace, though: the shallow roots want damp ground, not a standing pond, so give the water a clear way to drain off.
Soil
Bed the vines in acidic, organically rich peat and sand, kept consistently moist but well-drained. Aim for a pH of 4.0 to 5.5, far below what most plants will stand, which is exactly why cranberries need a patch of their own.
Temperature
This is a tough, cold-hardy vine, easy from -40°F to 86°F (-40°C to 30°C). Bitter winters do it no harm; it is summer heat above that ceiling, not the cold, that pushes it past its limit.
Humidity
Average humidity in the 40% to 70% band suits the plant fine. Air moving through the mat of runners counts for more than any precise figure, since stagnant, damp growth is what opens the door to fruit rot.
Feeding
Feed sparingly from spring through early summer with a food made for acid-loving plants. Cranberries want low fertility, so hold back: too much nitrogen drives runners and leaves and robs the plant of fruit.
Pruning
There is little to prune. Rake or mow out the surplus trailing runners in early spring to push the vine toward upright fruiting shoots and to keep air moving across the bed.
Repotting
A bog-container planting seldom needs moving. Refresh the acidic media every 2 to 3 years, and watch for roots winding round the pot or runners crowding the surface as the cue that it is time.
Size & spacing
The vines hug the ground, just 4 to 8 inches (10 to 20 cm) tall, yet they reach 1 to 6 feet (30 to 180 cm) across. Allow for that creep and give each plant room to mat out over the bed.
When to plant
The cranberry keeps to the northern seasons and settles into USDA zones 3 to 7. Set rooted cuttings or vine pieces out in spring once the soil can be worked, watch the pink and white flowers open in late spring, and gather the ripe red berries from early fall.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: Set rooted cuttings or vine pieces out in spring once the soil can be worked (April to May).
- Harvest: Blooms May to June with pink and white flowers; fruit ripens and is harvested September to November.
Hardiness
USDA hardiness zones: 3–7
Temperature: down to -40°C
Troubleshooting
Nearly every cranberry problem comes back to one of two things: soil that has slipped out of the acidic range, or a bed left too wet and stagnant. The plant tells on itself early, in the color of its small leaves and the firmness of its berries, so read those signs and you can usually fix the cause before the planting falls behind. Match what you see below, then act while it still counts.
Small leaves washing out to yellow or flushing red
Those small, leathery evergreen leaves draining of green or taking on a reddish cast is chlorosis, the look of iron locked out of the roots once the soil climbs above about pH 5.5. Check the bed with a meter first, then drop the reading back with elemental sulfur or a top-up of acidic peat. Watering with non-alkaline water and a food made for acid lovers brings the deep green back to the foliage.
Fix:
- Acidify soil with elemental sulfur or amend with acidic peat
- Irrigate with non-alkaline water
- Apply a fertilizer formulated for acid-loving plants
Red berries turning soft, sunken, and shriveled
A warm, soggy, stagnant bed breeds fungal fruit rot, and you see it as berries that go mushy under a thumb, dull in color, and dimpled where they should be plump and firm. Strip off and bin each spoiled berry, then loosen the bed so water and air can move through the dense mat. Reach for a registered fungicide only when the rot outpaces your hand-picking.
Fix:
- Improve drainage and air circulation
- Remove and discard infected fruit
- Apply a registered fungicide per label if severe
A thick green tangle of runners and barely a berry
When the bed becomes a dense carpet of trailing runners and few stand-up shoots rise from it, the culprit is usually too much shade or too much nitrogen, steering the plant into leaf and stem rather than fruit. Open it to full sun and pull back on the feed. Raking or clipping the surplus runners in early spring nudges the vine back toward the upright shoots that hold the flowers and berries.
Fix:
- Site in full sun
- Reduce nitrogen fertilization
- Rake or prune excess runners in early spring
Toxicity
Nothing to worry about here: the cranberry is non-toxic from root to berry. The fruit is a kitchen staple, and the extract is even fed to cats and dogs for urinary health. The most a greedy pet faces is a mild stomach upset from packing in too many berries at once.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
The small leaves and tart red berries hold nothing harmful for cats, and the fruit shows up in feline urinary supplements. A cat that bolts a heap of berries may get a passing queasy stomach and little else.
Dogs None
A dog can chew the firm berries with no harm, and the extract is given to them on purpose for urinary health. The one snag is a loose stool or a bit of gas after raiding a full bowl.
Horses Safe
The low creeping vines and the tart fruit they carry hold no danger for horses grazing past the bed.
Rabbits Safe
Rabbits can crop the small evergreen leaves and the berries without harm, though the fruit is better as a now-and-then bite than a steady ration.
Livestock Safe
Cattle, goats, and sheep take no harm from the trailing vines or their red fruit.
Birds Safe
Wild birds strip the ripe red berries off the vines freely and scatter the seeds, with nothing to fear from the fruit.
People Safe
People eat the bright red berries cooked, dried, and pressed to juice. Raw off the vine they are simply sharply tart, never unsafe.
No special handling needed; the plant is non-toxic, though eating large amounts of fruit may cause mild digestive upset.
Varieties
A small group of cultivars carries most of the cranberry crop, chosen for color, yield, and how well the berries keep. These are the names worth knowing.
Stevens
A heavy-cropping, disease-resistant hybrid that has grown into the most widely planted commercial vine.
Ben Lear
An early ripener valued for its deeply saturated red fruit and drawn on heavily as breeding stock.
Howes
An old Massachusetts heirloom whose firm, dense berries hold and store far longer than most.
Companions
Plant near
Lowbush blueberry (Vaccinium angustifolium): Shares the same very acidic, peaty, moist soil and growing conditions.
Lingonberry (Vaccinium vitis-idaea): Another acid-loving evergreen groundcover with matching soil and moisture needs.
Keep apart
Lawn grasses and most vegetables: They need near-neutral soil and cannot tolerate the very acidic, wet conditions cranberries require.
How to propagate
Cranberries almost always start from cuttings or by layering, both of which copy a known cultivar straight off the parent vine. Seed is possible but slow and unreliable, so few growers go that way.
Stem cuttingsModerate
Spring to early summer · Roots in a few weeks; 3 to 5 years to a full fruiting bed
This is the commercial route. Press 6 to 10 inch lengths of vine into damp acidic peat and sand from spring through early summer and hold them steadily moist. Roots strike within a few weeks, but count on 3 to 5 years before the mat knits together and fruits in earnest.
LayeringEasy
Spring to summer · One growing season to root
The vine layers without any prompting from you. A trailing runner sets roots wherever it rests on damp soil, so pin one down in spring or summer and it anchors into a fresh plant across a single growing season.
SeedDemanding
After cold stratification in late winter · Several years
Seed seldom repays the effort. It needs a cold spell in late winter to break dormancy, the seedlings inch along for several years, and they will not match the parent cultivar.
Myths
Cranberries grow underwater in flooded bogs.
The fruit forms on low trailing vines rooted in moist, well-drained acidic peat, not beneath standing water. Growers flood the beds only in short bursts, for wet harvest and winter cover. During the growing season the soil is kept drained, never sunk under water.
Cranberry berries are toxic to dogs and cats.
Plain berries do no harm to pets, and the extract is sold as a urinary supplement for them. Only a large helping might cause mild stomach upset, the same as nearly any fruit eaten by the bowlful.