What fruit to plant

Below are compact guides as to what fruit you could grow in your windowbox and how to grow it, with recommended cultivars that are known for their ease of growing, good flavour, size or hardiness. For obvious reasons I've not included any fruit trees here, but certain fruit bushes and shrubs may be possible depending on the size of your windowsill.

Currants

Berries (H-Z)

Berries (A-G)

Blackberries (Brambles)

Unfortunately due to their vigorous nature blackberries are not suitable for growing in a windowbox.

Vegetables

Cape Gooseberry - See Physalis

Cranberry

Cranberries prefer damp, boggy acidic soil, so if you’re prepared to give a windowbox over to them, it’s best to line your windowbox with a plastic liner (eg. Pond liner) punched through with only two or three small holes. You will need to use a peat-based compost or a soil mix manipulated to be make it more acidic*. Water copiously in summer, preferably with rainwater.
Plant: Pot-grown plants at any time of year.
Varieties: CN, Early Black, McFarlin

Blueberry

Blueberries require an acidic soil, so will need to be planted in a peat-based soil or that which has been manipulated to make it more acid. Cut unproductive stems back to soil level each year (in the spring)
Plant: Pot-grown or bare root bushes from autumn to spring, avoiding frosty weather
Varieties: Berkeley, Bluecrop

Gooseberry

Red, green or yellow gooseberries are available and many new varieties now also come without the savage thorns that make picking such a hazard. Gooseberry bushes require good drainage and preferably shelter from frost. Plant in fertile, well-drained soil .
Plant: Pot grown or bare root bushes from autumn to early spring
Varieties: Careless, Greenfinch, Whinham’s Industry

Cowberry

Cowberry, lingonberry or mountain cranberry is a groundcover plant with a mass of bell-shaped pink or white flowers in summer, followed by delicious claret-red berries. Requires an acidic soil.
Plant: pot grown plants in spring or autumn