When to Harvest Cranberries: The Bounce Test and How to Store Them

When the berries are ready

Cranberries color through autumn, turning from white through pink to a deep red, and they take their time about it. The berry reaches full size well before it reaches full color, and full color arrives a week or two before the flavor is at its best. As with most fruit that carries little starch, the sugars and the deep red pigments build in the last stretch on the vine, and picking early gives you fruit that is hard, pale-fleshed and sharper than it should be.

The trigger to start picking is a couple of light frosts. A frost or two firms the berries and deepens the color, and it is the traditional signal in every cold-winter region. What you must not do is leave them through a hard freeze, because berries that freeze solid on the vine turn soft and translucent when they thaw and will not keep at all.

Berries on the shaded inner part of the mat color later than those on the sunny edges. Go over the bed twice rather than stripping it in one pass, and the second picking is usually the better fruit.

The bounce test

A ripe cranberry has four small air chambers inside it, and those chambers are what make it float and what make it bounce. A firm, sound, properly ripe berry dropped from a few inches onto a hard surface will bounce back an inch or two. A berry that is bruised, soft, over-ripe or rotten inside thuds and stays put. This is not folklore; it is the principle behind the sorting machines used commercially, where the fruit is dropped over a series of barriers and only the bouncers make it across.

The test is genuinely useful at home because internal rot in a cranberry is often invisible from the outside. A berry can look perfectly red and be soft-centered, and one of those in a stored batch will spoil the fruit around it. Bouncing a harvest before you store it is five minutes well spent.

1. Set up a simple board Lean a smooth board at a shallow angle over a tray, or simply use a baking sheet on the worktop. Anything hard and flat works; you are only looking for the difference between a bounce and a dead stop.
2. Drop from about four inches (10 cm) Tip small handfuls from that height. Sound berries visibly rebound and roll away. Bruised or rotten ones land flat and stay where they fell.
3. Keep the bouncers, cook the rest The bouncers go into storage. The ones that failed are not usually wasted; unless they are actually rotten they are perfectly good cooked the same day in a sauce or a compote.
4. Repeat before long storage If you are keeping fruit for months, bounce it again after a few weeks. Any berry that has gone soft in the meantime is easier to find this way than by looking at them.

Floating works on the same principle and is a rough alternative: sound berries float on their air chambers while damaged ones sink. Dry the floaters thoroughly before storing, because wet fruit will not keep.

Picking dry

The home harvest is a dry harvest. Commercial beds are flooded and the vines beaten so the buoyant berries float free, which is fast, damages the fruit, and produces berries fit only for juice and sauce that must be processed at once. Nobody floods a garden bed to pick a few pounds of fruit, and dry-picked berries keep vastly better anyway.

Kneel at the edge and work through the mat with your fingers, lifting the runners and picking the berries off the uprights beneath. A wide-toothed berry scoop or comb speeds it up on a larger bed, drawn through the vines in the direction of growth so it combs rather than tears. Expect somewhere around a pound or two per square foot (5 to 10 kg per square meter) from a mature, well-managed bed.

Pick on a dry day, and after the dew has gone. Fruit picked damp goes moldy in store no matter how carefully you sort it.

Storing a crop that keeps for months

Cranberries store better than any other soft fruit a garden produces, and the reason is their high acidity and their benzoic acid content, both of which suppress the molds that ruin other berries within days. Unwashed, dry, in a single loose layer or a shallow ventilated container, they hold for two to three months in a fridge or a cold shed just above freezing.

Do not wash them until you use them. Do not seal them in an airtight bag, because trapped moisture is the one thing that will spoil them. Pick out any soft berry you spot, since one rotten fruit in a shallow tray will take its neighbors with it. For longer keeping, they freeze exceptionally well: spread them dry on a tray, freeze until hard, then bag them, and they hold a year with almost no loss. Frozen cranberries go straight into cooking without thawing.

Any berry that fails the bounce test but is not actually rotten should be cooked within a day or two. It has the same flavor; it simply will not survive storage.

Yield, and what to record

A cranberry bed does not give a real crop for three or four years. The first year is roots, the second is runners, the third brings a scatter of flowers on the first uprights, and only by the fourth does a closed mat carry a proper harvest. Knowing that in advance is what stops people digging up a perfectly healthy bed in its second summer for producing nothing.

Record the date of the first frost, the date you picked, and the rough weight from the bed each year. Add a note of how much sand you spread and how hard you raked the previous spring. Because a cranberry crop reflects work done a full year earlier, that pairing of dates and weights is the only reliable way to tell whether your management is actually improving the bed.

Note where in the bed the fruit actually came from. Concentrated fruiting along a sunny edge and none in the middle is the clearest possible evidence that the mat needs raking out.