Cranberries are the staple fruit of Christmas, creating the sauce synonymous with turkey or adding warmth to winter punches, relishes and jellies.
The plant was first named by early European settlers in America who felt the expanding flower, stem and petals resembled the neck, head, and bill of a crane.
Most cranberries are still grown in boggy areas of North America and eastern Europe. They’re not widely grown in this country, although specialist fruit nurseries may offer a few types and the RHS also sells them.
“Cranberries like boggy soil conditions and it’s quite difficult to create an environment in which they thrive in the UK,’ says Leigh Hunt, principal horticultural adviser with the RHS. “But we can control the moisture and soil type by planting them in containers.”
If you have problems with drainage in your garden, the cranberry might actually be for you. They need extremely acidic soil, with a pH of less than five, and semi-bog conditions. They prefer sun but will also withstand light shade. If you’re planting them in the ground, dig a hole 40cm (16in) deep and line the base and sides with plastic sheeting. Fill with an ericaceous compost and mulch with 5cm (2in) of sawdust or wood shavings. Punch a few small holes in the sides of the plastic just above the bottom to allow water to seep out. If you can, use rain water to thoroughly wet the compost and trample it like grapes until the soil is soaking.
“Keeping them well watered is really important and early to mid-summer is critical,” adds Leigh. “Most days you will need to check the pot. They have a shallow root run so a pot 12 inches deep would be sufficient and ideally you want a pot which is wide but shallow.”
In spring, feed the plants with sulphate of ammonia, sulphate of potash and bonemeal and top-dress with ericaceous compost. If you are growing in pots you can control the conditions more effectively by spring planting in peaty ericaceous compost enhanced with around 10 per cent lime-free grit. You’ll need to keep the plants really wet, so stand the pots in wide saucers that remain topped up with water, particularly rainwater, as tap-water contains too much lime.
Feed the plants every week during the growing season with a product specifically formulated for acid-loving plants and you should be harvesting the berries in September and October. They will keep in the fridge for a good few weeks or you can freeze them or pop them in the oven on its lowest setting for a few hours to dry them.