Plum
Cultivars and varieties:
Prunus domestica 'Czar' - Doesn't need sun to ripen, will grow and fruit on a north-facing wall.
Prunus domestica 'Early Rivers'
Prunus domestica 'Marjorie's Seedling'
Prunus domestica 'Oullins Gage' [AGM] (Dessert) - Self-fertile.
Prunus domestica 'Victoria' - The most commonly grown plum. It's self-fertile and will grow well on a north-facing fence or wall.
Seeds to sow now:
Indoors or in a greenhouse
Antwerp hollyhock, Fig-leaved hollyhock, Hollyhock
Bristly hollyhock
Outside
What else to plant now:
Apple & pear trees (bare rooted)
Roses (bare rooted)
Cyclamen
Outside under cover
Onion
Pea
Potato Onion