These fruits are also called heathland berries as they occur in the wild on heaths, often in peaty acid soil and exposed to the elements including lots of rain. With this in mind you can grow good harvests of these tasty fruits, by imitating these natural conditions.
Planting Cranberries and Blueberries
Being acid-loving plants (particularly cranberries) it’s advisable to grow this fruit in containers, unless you know you have acidic soil in the garden. (If you have healthy established blue hydrangeas, or healthy, non-yellowing-leaved rhododendrons). Water your potted blueberry or cranberry plant well (preferably with rain water) in the container it arrived in, while you prepare to replant in containers or into the ground.
Choose a 30cm (12in) diameter pot to transfer and ensure it has drainage holes at the bottom.
Fill your pot with ericaceous compost. As you fill the pot, place the plant at a height, so that the soil mark on the main stem(s) is level to about 2cm (3/4 in) from the very top of the pot. Fill the pot to this level and firm the compost down so that if you tug at the tree, there’s quite a bit of resistance.
Water the top 2cm (3/4 in) of the pot and let that absorb into the soil and repeat. Set the pot in as sunny a position as possible. As the tree grows you will need to re-pot again. Try to choose a dry but dull day to do this. Follow the instructions above placing the tree into a 40cm-45cm (16-18in) diameter pot.
NB – Don’t be tempted to plant patio trees directly into a large 45cm (18in) pot. If there’s too much surrounding soil to the pot, the soil can get wet and cold – which is not good for developing roots. Better to pot up in degrees (e.g first a 30cm (12in) pot then a 45cm (18in) pot as the tree grows and you notice roots just start to form around the soil edges, if you lift the pot.
In open soil
Dig a planting hole 15cm (6in) wider than the root system once it has been spread out, and to a depth whereby the soil mark from the nursery on the stem of the young tree will be just covered. This should mean that the graft union (the knobbly part at the base of the stem) is about is 12-15cm (5-6in) above soil level when you have finished planting. Fork into the sides of the hole which will encourage the roots to penetrate the surrounding soil and establish well. After placing the plant in the hole, spread out the roots and add layers of soil, firming down with your foot. Repeat until you’ve filled the hole with soil. The tree should be firm enough in the soil that it does not up-root when you pull the main stem and it shows resistance. Water the area generously after planting and add a layer of warming and moisture-locking mulch around the tree, making sure that the mulch does not come into direct contact with the main stem(s).
NB- For more than one plant, space Blueberries 1m (3ft) apart, and Cranberries 30cm (1ft) apart.
Feeding Cranberries and Blueberries
Add Bonemeal at planting. If you notice that foliage is yellowing – it is probable that the soil is not acidic enough. Amend this by feeding with ericaceous plant food according to packet instructions.
Watering Cranberries and Blueberries
Water well in dry spells, especially plants grown in containers. After a while tapwater will build up too much alkalinity in the soil, much to the dislike of Cranberries and Blueberries.
If you have a water butt in the garden- collect rainwater and use this to water your Cranberries and Blueberries plants. (Rainwater is at the ideal acidity for these heathland fruits.)
Training Cranberries and Blueberries
In winter, cut out any damaged or dead branches. It is also recommended that each year, a few old stems that have borne fruit are cut back to ground level to promote new growth in the following spring.
The perfect time for picking is when your fruit is fully coloured and shiny, if the surface is dull then you have waited too long. Unfortunately not all fruit will ripen at once so you will need to go over your bushes at least 2-3 times.
The largest fruit is borne on the thicker, more vigorous shoots. Prune in early March when the fruit buds are visible. Young plants need little pruning in the first three years. Just remove any horizontally growing shoots, weak stems, as well as dead or diseased wood, to produce an open centred bush. Prune to an upright shoot or a fat healthy bud. On mature plants remove thin, twiggy stems as well as any damaged or diseased shoots, or stems close to the ground. To maintain a strong productive shrub, cut back some of the older branches to the base and others to strong upright shoots. Although these blueberries are hardy, plants in pots should be moved to a sheltered position during winter to prevent the roots from freezing. Wrapping pots in fleece or bubble-wrap will give extra protection.
Pests and Diseases of Cranberries and Blueberries - Birds, Aphids